Transcript for:
Human Anatomy and Physiology Overview

what's going on besties this is everything you're going to need to know all in one place when it comes to the ait's version 7 science portion of the exam more specifically human anatomy and physiology let's get started so let's begin by talking about the different parts of this system when you breathe in air is going to enter through your nasal cavity where it's going to be warmed humidified and filtered by the mucus and your hairs these structures include visible nasal hairs and microscopic cyia which are hairlike structures next up the air is going to reach our fairings which is the crossroads between where food is going to go down the esophagus and air is going to go down our larynx air is going to travel down our larynx which is also known as our voice box before It ultimately reaches our trachea it's a very important to note is that food should be traveling down our esophagus and not our trachea the epig is going to play a critical role when it comes to preventing food from getting into our trachea what's really cool about our trachea is that it has this intriguing cylindrical tube supported by these Rings also known as carage which is going to help keep that airway open and allow air to pass through the tracha is going to extend downward splitting into primary broni one leading to each lung speaking of the lungs there are two of them divided into sections known as loes you're going to find three loaves over here on your right lung and two loes located on your left lung most notably that left lung is also going to have something what we call the cardiac Notch it's a small indentation that accommodates the heart making the left lung slightly smaller than our right our primary broni is going to split off into our secondary broni then our tertiary Bron ey and then down into our brachioles so as we move down this system you're going to find find that the space that that air has to get through is going to become smaller and smaller and smaller as we move even further down you're going to see our terminal brones are going to lead into our respiratory brones that are ultimately going to lead down into our alvear ducts each Alvar duct is going to be surrounded by clusters of alvear sacks which resemble grapelike structures a comparison that many of them make whenever they're looking at this particular part of the structure contained in each one of these sax we're going to find Alvi this is where the actual process of gas exchange takes place you're going to need to know two terms when it comes to the te's the conducting Zone and the respiratory zone in the lungs the conducting Zone and the respiratory zones serve distinct functions but are still interconnected the conducting zone is going to include structures like our trachea our broni and our terminal bronchial which facilitate the passage of air to the respiratory zone Zone but do not actually participate in the gas exchange we like to call this space anatomical Dead Space since no gas exchange takes place here this Zone's primary role is to warm humidify and filter the air before it reaches the deeper parts of our lungs as we move down to our respiratory zone this is where the actual gas exchange is going to take place and is going to include structures like our respiratory bronchioles alvear ducts as well as our avioli the avioli which are tiny sacklike structures are pivotal as these are the sites where oxygen enters the blood and carbon dioxide is removed the extensive surface area of the Alvi combined with their rich blood supply makes them highly effective for gas exchange a critical process for maintaining the body's respiratory and overall metabolic balance so as we discussed the circulatory system is intimately connected with our respiratory system the red blood cells traveling through our capillaries pick up that oxygen that we breathe in to distribute it throughout the body and they also collect carbon dioxide as a waste product of our metabolic processes to be exhaled however the respiratory system doesn't work in isolation it collaborates with other body systems as well the skeletal system which includes our ribs help form a protective cage around our lungs additionally our muscular system plays a crucial role when it comes to respiration these structures include intercostal muscles which are located in between our ribs the diaphragm that is situated beneath our lungs and the muscles of our abdominal wall all of these muscles work together to expand and contract the thoracic cavity aiding and breathing while you can control your breathing voluntarily you'll find that it operates involuntarily most of the time when you think about it you don't really think about breathing it just kind of happens this is because our nervous system system manages that autonomic control using pH levels in our blood to help regulate our breathing speaking of pH the pH scale measures hydrogen ion concentration on this scale acidic substances indicated by our lower numbers on the scale have higher hydrogen concentration whereas basic substances which have higher numbers on our scale are going to have lower hydrogen concentrations therefore an increase in carbon dioxide is going to lead to higher levels of hydrogen ion concentration in our blood making the blood highly acidic this change is going to be detected by sensors and Those sensors are going to send signals to our brain in response the brain is going to regulate our intercostal muscles our diaphragm as well as our abdominal muscles to increase the rate of breathing as well as the depth of breathing this adjustment is going to help restore and stabilize the blood pH to around 7 .4 maintaining homeostasis I want you to consider the adjustments your body makes during exercise it's remarkable how finely tuned our system is enabling the increase of our breathing rate and depth in order to match our body's metabolic demands and then lastly we're going to discuss the mechanisms of breathing as well as profusion so when we talk about breathing mechanics we're really talking about two main processes we're talking about inspiration which is inhalation meaning that we're breathing in that's inspiration and then we have expiration which is also known as exhalation meaning that we're breathing out these are facilitated by coordinated actions of the diaphragm and our intercostal muscles so when we talk about inspiration this is an active process where the diaphragm and external intercostal muscles are going to play critical roles the diaphragm which is that Dome shaped muscle that's located below our lungs is going to contract and flatten downwards this contraction is going to increase the vertical dimensions of our thoracic cavity simultaneously those external intercostal muscles which are located in between our ribs are going to contract and they're going to pull that rib cage upwards and outwards this overall action is going to expand that thoracic cavity in both the lateral and anterior posterior Dimensions this increase in volume is going to create NE negative pressure relative to the atmosphere causing air to flow into our lungs in contrast expiration is usually a passive process during normal restful breathing expiration involves the relaxation of our diaphragm and our external intercostal muscles as that diaphragm relaxes it's going to move upwards back into the original Dome shape that we saw before and the rib cage is going to move downward and inward as the external intercostal muscles relax this overall reduction of the volume inside of our thoracic cavity is going to increase the pressure inside the cavity compared to that of the outside atmosphere pushing that air outside of our lungs it's important to note that during forced expirations such as like we see with vigorous exercise or even coughing that expiration process is going to become more of an active process this brings us to our next point Point profusion and ventilation are two critical aspects when it comes to pulmonary physiology that work together to optimize gas exchange in the lungs ventilation refers to the movement of air in and out of our lungs this process ensures that fresh air rich in oxygen is going to reach our Avi and profusion is going to involve the flow of blood to those alv capillaries in this process oxygen depleted blood is brought to the lung from the body via the heart to be oxygenated and have carbon dioxide removed the ideal scenario is when ventilation which is our air flow and profusion which is our blood flow are mashed and balanced in the various regions of the lungs however sometimes this process can become imbalanced and that's when we see hyperventilation and hypoventilation so hypoventilation occurs when the ventilation is inadequate in relation to the body's needs you're going to see a red uced air movement into and out of the lungs leading to an elevation in our carbon dioxide and a decrease in our oxygen we also refer to these as hypercapnea and hypoxia so I want you to think about it what happens if we're not breathing appropriately we're breathing less than what our body needs hence the word hypo well we're not going to be able to Exhale enough of that carbon dioxide from our respiratory tract so if we're not able to Exhale that off we're going to seen increase in our CO2 and also we're not going to get enough oxygen in so we're going to see a decrease in our oxygen because of that mechanism not working appropriately so next let's talk about hyperventilation and this refers to a state where the rate and the depth the breathing is increased excessively leading to increased expulsion of CO2 known as hypocapnea and a rise of oxygen in our blood known as hyperoxia this type of breathing can lead to respiratory alkalosis which is a condition where the pH of the blood increases due to those lower CO2 levels because as we know CO2 is a key component when it comes to our body's acidbase balance it's important to note that both hypoventilation and Hyper ventilation disrupt the normal process of breathing as well as the balance of oxygen and carbon dioxide in the body the cardiovascular system plays an essential role in so many body processes first let's discuss how blood which serves as the vehicle for transporting glucose and gases through our body works there's a common misunderstanding about blood and it's important to note that human blood is always red it's a shade that can either be a dark red or a lighter red depending on the oxygen concentration found inside it in many educational diagrams veins and arteries are depicted as blue and red to indicate lower and higher oxygen levels however this coloring is just a diagrammatic tool and does not reflect the actual colors of blood veins and arteries the veins that you see peeking up underneath your skin may appear to have some blue and green Vibes but that's just a sneaky optical illusion the human blood is quite a multitasker it juggles between maintaining pH temperature and osmotic pressure all vital for keeping the internal environment steady also known as homeostasis blood is also the body's internal FedEx system delivering hormones nutrients and gases wherever they are needed so blood is made up of all kinds of really interesting stuff take plasma for example plasma is the liquid portion of our blood it's basically a cocktail of water proteins salts and lipids then we have our cellular Heavy Hitters our red blood cells are our transport of our gases and our white blood cells help fight off infections but what about platelets platelets really are the unsung heroes because they help the blood clot whenever we scrape our knee how does blood get that signature red color we can thank hemoglobin for that which is an iron-rich protein in red blood cells providing its stylish Hue so as we dip our toes into the circulatory system we're going to focus on how all of these components circulate around our bodies so arteries are the roadways that carry the blood away from our heart just remember a is for away they usually transport oxygen rich blood though there are some exceptions to that rule veins on the other hand bring that blood back to the heart I like to remember this as using the word verb veins efficiently return blood they typically carry that oxygen poor blood back to the heart however what's interesting is both arteries and veins tend to flip the script when it comes to pulmonary circulation this type of circulation is when pulmonary arteries carry oxygen poor blood and pulmonary veins carry oxygen rich blood this is the only exception to that rule and then last up we have capillaries capillaries are tiny little blood vessels where oxygen is delivered to organs and tissues and carbon dioxide hop off for their ride back to the lungs so if we're examining a patient's heart you're going to notice that the right side is actually on our left side right but we have to really it's important to note that we're always looking at the patient's right or the left not from our own perspective so when we're talking about the right side of the heart we're talking about the deoxygenated side the deoxygenated blood side this is where that blood is going to get circulated into our lungs and then come back into the left side of the heart which is the more oxygen rich side sometimes due to congenital heart conditions these two different types of blood tend to mix together we're going to explore this a little bit more later so if we take a look at our heart we're going to notice that we have four chambers we have our right atrium and our right ventricle on one side and we have our left atrium and our left ventricle on the other side a handy nemonic that I like to remember when it comes to the cardiovascular system is that a for Atria comes before V for the ventricles in the alphabet which helps us remember that the Atria are on top and our ventricles are on the bottom so the Atria have thinner walls in comparison to the thicker walled ventricles that we see below the heart is also equipped with valves like we see here these valves are like oneway doors they not only separate the chambers but they also prevent blood from flowing backwards let's take a closer look at how blood flows throughout our heart gets into the pulmonary system and then comes back before it gets pumped out into our body the aits is going to test you on blood flow through the heart it is imperative that you know this process and you have a good understanding of it because you're going to need to know it not only the atits but for most of the healthc Care professions that you'll be going into so let's begin with the blood that's circulating in our fingertips this blood is deoxygenated and needs to return to the heart so that it can be sent to the lungs to pick up oxygen blood is going to return to the heart via the venne Caba whether that's inferior or Superior the inferior venne Cava is going to collect blood from the lower half of our body including our legs our back our abdomen and our pelvis the superior venne Cava is going to collect blood from the upper half of our body including our head our neck our upper Limbs and our upper torso the journey starts when the blood enters into to our right atrium once it's there that right atrium is going to contract and it's going to push blood through our tricuspid valve once it passes that tricuspid valve it's going to enter into our right ventricle and that right ventricle is going to contract propelling that blood through that pulmonary valve which is located right here into our pulmonary artery which again is our deoxygenated blood going through an artery consequently Landing into our lungs once that blood is in our lungs it's going to pick up that oxygen that it got from the environment and it's going to offload that carbon dioxide that it pulled up from the metabolic processes in our body once that blood is oxygenated it's going to return back to the heart where it's going to be pumped to nourish our entire body oxygen rich blood is going to return via our pulmonary veins into our left atrium once it's there that left atrium is going to contract and it's going to push that blood through our mitro valve which is also known as our bicuspid valve from there the blood is going to be pushed down into our left ventricle and that left ventricle is then going to contract forcefully to pump that blood out through our aortic valve and then into to our aorta the aorta is a major artery that that carries oxygenated blood to all parts of the body ensuring that our tissues as well as our organs receive the oxygen that they need and order to function speaking of oxygenation it's crucial not to overlook that the heart itself requires a dedicated blood supply to receive oxygen and glucose this vital Supply comes through coronary arteries which branch off from our aorta these arteries transport blood into tiny capillaries that weave throughout the heart muscle delivering oxygen and nutrients after the heart cells have used up that oxygen they are going to transport that deoxygenated blood back to the heart through the coronary veins this deoxygenated blood is going to return to our right atrium via the coronary sinus allowing it to circulate back through our blood picking back up oxygen and delivering all of those waste products that it picked up along the way before we delve into the heart's electrical conduction system it's essential to recognize that various conditions can disrupt the heart's normal function some of these functions anatomically alter the flow of blood within the heart we discussed previously that sometimes we see blood is going to be mixed between deoxygenated and oxygenated blood we call this sepal defects this is when the septum the muscular wall that divides the heart's left and right sides have some kind of abnormality a sepal defect involves the opening that allows oxygen rich blood and oxygen poor blood to mix depending on the defect size the mixing can lead to significant issues including abnormal heart rhythms even maybe stroke as well as heart failure if we have severe cases more specifically an opening that's found on their inter atrial septum is going to result in atrial sepal defects or mixing of blood occurs between the left and the right Atria similarly a opening between our interventricular septum is going to lead to ventricular sepal def defects which involves the mixing of blood in our ventricles treatment options can include medications to help manage those symptoms or we may even have to do surgical interventions now let's delve into the various components of the electrical conduction system of the heart our starting point is our sinoatrial node and that's situated up here in the right atrium close to where it meets with the superior venne Cava this note is essential when it comes to the heart's primary pacemaker marking the commencement of the electric iCal conduction pathway the activation of this SA node triggers a sequential contraction of atrial myocytes it's also crucial to understand the role of the fibrous tissue found in the septum which separates the left and the right sides of our heart including our Atria as well as our ventricles this separation is vital as it hinders direct electrical signal transmission between those heart sections following an essay note we encounter a structure known as Bachman's bundle it is characterized by its ability to transmit high-speed signals extending from the sa Noe across that atrial subtile wall into our left Atria the internodal pathway consists of three routes we have the anterior middle and the posterior these pathways are chiefly involved in conveying that electrical impulse from the SA node all the way down to our atrial ventricular node the atrial ventricular node is situated in the right atrium but this time it's going to be near the coronary sinus and our tricuspid valve this clusters of cells is specialized to momentarily pause that electrical signal from the SA node before it can proceed down into the ventricles this intentional delay is crucial because it provides sufficient time for the Atria to thoroughly contract and ensure that all of that blood is going to reach the ventricles before the ventricles themselves contract following the ab node we encounter the bundle of His which is comprised of another group of high-speed transmission cells these cells extend from The Av node traversing partially through that right atrium and then into our interventricular septum where they're going to Branch off into our left and our right ventricles in individuals without cardiac abnormalties these Pathways represent the sole Communication channel between our Atrium and our ventricles like we discussed the bundle of His is going to split off into two distinct Pathways we have our right bundle branch and our left bundle branch as you can guess the right bundle branch is going to transmit signals to the right ventricle and the left bundle branch is going to transmit signals to our left ventricle lastly we turn our attention to the preni fibers which project from both the right and the left bundle branches and they directly interface with the heart's meiocytes their primary role is to initiate depolarization within the muscle cells triggering that contraction that we see in in the cardiac muscle similar to the way that atrial myocytes function the ventricular myocytes receive and further transmit those electrical signals to adjacent cells at a slower Pace compared to that of the rapid transmission observed in the high-speed bundle branches an essential characteristic to understand is that the system has its own inherit pacemaker capability of its various cells which essentially govern the heart rate virtually all components of the system we've discussed possess their own intrinsic pacemaker rate what's interesting is that this rate is going to decrease as we progressively move down the electrical pathway you can essentially think of this as the body's contingency plan should a higher pacemaker fail to initiate a lower level pacemaker eventually is going to activate ensuring that the heart's contractions continue an easy pneumonic to remember the order of the heart's conduction system is strong arteries benefit bodies performance where the S and strong stands for our SA node the A and artery stands for our av node the B's and benefit and body stands for our bundle branches and the p and performance stands for our pereni fibers starting with our SA node that is our heart's primary Pacemaker and it has a natural pace of 60 to 100 beats per minute and it can adjust this pace depending on the body's demands following in sequence we have the AV node which is also known as our secondary pacemaker it has its own intrinsic rate of 40 to 60 beats per minute so if the SA node was to fail then the AV node is going to be the next node to kick in and it's going to beat at that intrinsic rate of 40 to 60 beats per minute so that means when we're looking at rhythms originating from The Junction which is where the AV node sits also known as our junctional rhythms we're going to see rhythms that are a little bit slower and then lastly we have our penji fibers which is our last ditch Pacemaker and this is going to be at an intrinsic rate of 20 to 40 beats per minute while these slower rates further down our system are not ideal and potentially life-threatening they afford the body additional time for corrective measures for the te's you're going to need to know the basics when it comes to an ECG we're going to start with our ISO electric line and this line acts as a critical Baseline representing the moment when the heart's electrical activity shows no net movement effectively a zero electrical potential State this Baseline is also essential for interpreting the heart's electrical signals accurately it allows healthc Care Professionals just like you one day to distinguish between the various phases of heart activity such as depolarization and repolarization the first minor Peak that we encounter on this ECG is known as our p-wave it's then proceeded by this very prominent formation known as our Qs complex and it's ultimately going to conclude in the subsequent minor peak of our t-wave this p-wave signifies atrial depolarization and this is when the two atria contract following that we have our Qs complex and this signifies ventricular depolarization the period where the heart's ventricles contract essentially depolarization is just a fancy way of saying contraction how do we differentiate between these two waveforms a helpful hint is that the QRS kind of looks like an upside down V so that inverted V ultimately stands for ventricles V and ventricles V in our curus complex and finally we have our t-wave and our t-wave represents ventricular repolarization marking the period when the ventricles are in the process of relaxing it's essential to remember that each depolarization phase which leads to contraction is invariably going to be followed by a repolarization phase allowing for relaxation so this concept brings up an intriguing question when does atrial repolarization occur if if the QRS complex is associated with ventricular depolarization and the t-wave is associated with ventricular repolarization when might the atrial repolarization occur so what happens is this atrial repolarization happens concurrently during the time frame of that QRS complex that QRS complex being such a pronounced structure overshadows that atrial relaxation this is because the ventricles contract more forcefully than we see with the Atria effectively concealing atrial repolarization inside that QRS complex and lastly we're going to talk about systolic and diastolic pressure so blood pressure measures how forcefully blood is pushing against the walls of Our arteries as the heart circulates it throughout the body a blood pressure reading is going to consist of two numbers our systolic and our diastolic the systolic blood pressure is going to be that top number you see on your reading reflecting the peak pressure in the arteries when the heart contracts and pumps blood out of the heart this ultimately indicates how hard the heart has to work in order to circulate that blood a high systolic reading may suggest the heart is exerting too much effort a potential indicator of hypertension on the flip side our diastolic blood pressure is the bottom number that we see and this represents the lowest pressure in the arteries when the heart is relaxed between beats it measures the resistance to blood flow within Our arteries elev ated diastolic pressure could mean that the arteries are either narrow or they could even be too stiff increasing the risk for heart disease stroke as well as other health issues a typical blood pressure should be around 120 over 80 but ideal ranges are going to vary depending on the individual as well as age structurally the nervous system is divided into two main regions we have the central nervous system system and the peripheral nervous system the CNS is comprised of the brain and the spinal cord functioning as the primary Command Center for processing information in contrast our pns includes all of our nervous system elements such as our nerves distributed throughout the body the pns gathers sensory information and relays it to our CNS which then processes that data and coordinates motor responses and regulates bodily functions as we look at the brain we're going to categorize it into three main regions we have the hindbrain the midbrain and the forebrain starting with our hindbrain it is composed of three main areas we have the medulla ablang the ponds and the cerebellum the medulla ablang which is this region right about here regulates vital functions including things like breathing blood pressure and heart rate the ponds also supports these functions and help coordinate communication between our forbrain and the cerebellum and then lastly our cerebellum plays a key role when it comes to balancing and coordinating movements an easy way that I like to remember these three things is the medulla manages the pawn passes and the cerebellum coordinates as you know the medulla manages essential bodily functions that we talked about when it comes to motor control monitoring heart rate as well as modulating breathing the pwns passes messages between the brain in the body and it plays a critical role when it comes to the patterns of breathing and participates in our sleep cycles and then lastly the cerebellum coordinates complex voluntary movements it controls balance and IT calibrates muscle activity to ensure smooth and balanced motion next up let's talk about our midbrain which is located deep within the brain it's essential for maintaining alertness and managing our sleep wake cycle as well as overseeing some of our motor activities an easy way that I like to remember how the midbrain functions is I like to use the pneumonic mid controls which stands for movement involvement in the Sleep awake cycle and detection of auditory and visual reflexes starting with movement the midbrain is involved in motive movements and coordination particularly eye movement and other reflexive responses when it comes to the involvement of our sleep wake cycle it plays a crucial role when it comes to maintaining our alertness and regulating that sleep wake cycle and then lastly we have detection of auditory and visual reflexes the midbrain processes that audit and visual signals contributing to the reflective responses we get whenever we're introduced to a stimuli next up we have the four brain which contains our cerebrum which is the largest and most developed part of our brain it features a distinct fissure that actually runs down the middle of our brain dividing it into two hemispheres we have the left hemisphere and the right hemisphere but what do we mean by it's the most developed part of our brain well primarily the cerebral hemispheres houses the primary motor and sensory cortices when I mention the word cortices I'm referring to the plural form of Cortex the cortex is simply the cerebrums outer layer it's about 1 to 5 mm thick and it's actually composed of gray matter as you can see here in this picture when we're examining a neuron there's a few key components that we need to identify we have the cell body we have the axon and we have the axon terminal the axon terminal is typically going to connect to another neuron what's important to note is that the axon is enclosed in this milon sheath which is made up of fats and lipids and they appear to be white therefore in the brain we have gray matter which consists of the neuron cell bodies in the area where the synapsing actually occurs while white matter is primarily composed of those axons in the milon sheaths this distinction is crucial because gray matter is where information is integrated and processed essentially where the brain makes sense of the incoming data in contrast white matter acts like highways simply facilitating that rapid transmission of signals from one area of the brain to another so as we talked about before within our cerebral hemispheres lies the primary motor and sensory cortices representing the highest level of neural activity for example the primary motor cortex located in our frontal low if you take a look here that's that purple area that deep purple area right there this is the area that's crucial for initiating voluntary or conscious motor movements for example if you decide to start walking this initiation actually occurs right here in our brain marking it as the highest level of which motor activity is controlled similarly the sensory cortex processes incoming information from both our external and internal environments enabling us to consciously be aware of what's going on this actually occurs right here where you see this dark teal on our brain this area represents the highest level of sensory information integration for example when you touch a hot surface it's that sensory cortex that processes this sensation alerting you of the Heat and enabling you to react appropriately to get your hand away from that hot surface within the sural hemispheres we find association areas that augment the functions of both our primary motor and our sensory cortices these areas are going to integrate paths and present information enabling comparison and contrast of what is already known this process is going to enrich our understanding and providing us a deeper analysis of complex information for instance while the primary motor cortex May initiate basic actions like walking it's really that Association area that enhances the capability by allowing the sequencing and planning of more intricate tasks so let's take for example if you were dancing in ballet or EX executing a series of martial art movements the association area of the mortar cortex would be engaged enabling the planning and sequencing of these more elaborate activities when we're examining the sensory cortex which is located up here in our parietal lob this Association cortices play a crucial role when it comes to helping you interpret the type of sensory information that you're going to encounter for example using the earlier example of touching that hot stove the primary sens cortex alerts you of the sensation of heat but it's the association cortex that then further analyzes that information it assesses the temperature and considers whether it's merely just warm or scolding hot this area also draws upon past experiences like previous encounters with heat to help us identify and understand the sensation thus that Association cortex is integrated into our memories and current sensation it's going to Aid in our primary sensory cortex the cerebral hemispheres are also going to serve as the foundation of our conscious experience when we become consciously aware of something it is because that sensory information or thought processes have reached our cortex as we discussed before this cortex is that thin layer about 1 to 5 mm thick enveloping the outermost part of our hemispheres it is within this critical layer that our Consciousness emerges allowing us to become more aware of the experiences around us while the deeper areas of our brain may receive sensory information or initiate decisions about motor movements these processes do not enter our conscious awareness unless they reach our cerebral cortex therefore for us to consciously be aware of Sensations thoughts and actions they must be processed through the superficial layer of our cerebral hemispheres this is where all elements necessary for conscious awareness are integrated and interpreted the cerebral hemispheres also hous our lyic system which plays a crucial role when it comes to memory and the emotional dimension of behavior let's consider various emotional aspects of our daily life such as relating to eating relationships reproduction and the fight ORF flight response it's the lyic system that influences all of these furthermore the lyic system is integral to the highest level of cognitive function found in our cerebral hemispheres cognitive functions Encompass activities such as planning making judgments experiencing emotions reasoning and ensuring that behavior is appropriate to the context much of our cognitive processing occurs in the frontal lobe specifically known as the prefrontal cortex if we have damage that occurs in this area it is going to significantly impair our Behavior planning and other cognitive functions highlighting its import importance in managing complex behaviors and decision-making processes and lastly we have our occipital low which is back here and we have our temporal lobe which is right here the aital lob's primary functions include processing integration and interpretation of visual and vision stimuli this area houses the primary visual cortex where visual signals are received from our retinas and our temporal lobe is important for processing auditory information and it's home to our Prim primary auditory cortex it plays a key role in the formation of our longterm memory it's also involved in speech comprehension through our wori areas which is on the left temporal lobe and it also assists in recognizing and processing emotion and language so I wanted to give you an easy memory trick when it comes to remembering what each lobe does so we're going to start with the frontal lobe I want you to think forhead frontal lob it's symbolizing our deep thought and decision-making processes so when comes to the parietal lobe I want you to associate it with a parachute because it's covering the top part of our head and it's related to the sensory input from our body below our occipital low which is located here in the back connects to our Optics and our ocular focusing on our role when it comes to vision and then lastly when it comes to the temporal low which is kind of right here on the sides I want you to link it to Tempo when it comes to music reflecting on its connection when it comes to hearing and rhythm in speech and memories so now that we've covered the central nervous system what about that peripheral nervous system from a functional perspective the pns can be further categorized into two main parts we have our somatic nervous system and we have our autonomic nervous system the somatic nervous system is primarily responsible when it comes to the motor functions of our skeletal muscles both encompassing the voluntary actions that are under our conscious control and the somatic reflexes which are not on the other hand we have our autonomic nervous system which primarily manages our body's internal environment regulating functions related to our gastrointestinal expiratory and endocrine systems as well as smooth and cardiac muscle activities it also governs autonomic reflexes and the autonomic nervous system can indeed be split even further yes there's more divisions taking place we have the sympathetic nervous system and we have the parasympathetic nervous system the sympathetic nervous system which is the shorter name of the two is easy to remember because it's associated with the rapid fight or flight response instead of that typical example of running from a bear let's say you're suddenly standing in front of a vending machine your snack has just gotten stuck and it's Out Of Reach while there's a long line forming behind you for those who also want to get some snacks this frustrating scenario could definitely kick that sympathetic nervous system into overdrive this reaction could increase your heart rate it could increase your respiratory rate and your digestive system well that's going to take a backseat to all other things that need to take place first I mean after all you're dealing with an immediate stress be it a bear or a rebellious vending machine digesting food is not your body's main priority now when it comes to our parasympathetic nervous system denoted by the longer word it's frequently referred to as our rest in digest system in this state your heart rate is going to slow down and digestion is going to occur your body as it enters into that phase of rest and Recovery often the parasympathetic and sympathetic systems have inverse effects on the same organs essentially balancing each other out in their regulation of bodily functions let's discuss the two primary types of cells found in the nervous tissue of both the Central and peripheral nervous systems that you're going to need to know when it comes to the teas typically when we think about cells in the nervous systems neurons are the first thing that come to mind while we do recognize that there are various types of neurons let's take a look at the basic structure when it comes to a general neuron as we talked about before a neuron houses a cell body which encompasses most of the neurons organel as well as its nucleus we also have things known as dendrites and these are branch-like structures that receive the signals from other cells and then next up we have our axon which is our long body right here and the way that I like to remember it is I like to think of the phrase axon away because axons are the long f fibers that carry signals away from the neuron to other cells the point in which neurons communicate with one another is known as a synapse and that's done right here at the axon terminal another essential cell you're going to need to know are G cells structurally there are significant emphasis on how gal cells help hold neurons in place the word glea itself deres from the Greek word meaning glue however G cells are far more significant than that some of these cells help maintain the chemical balance balance necessary for signaling between our cells and help sustain that blood brain barrier which prevents many substances in the body from entering our nervous system others produce myin sheath a protective coating that wraps around our neurons axons insulating them in enhancing signal transmission additionally some gal cells generate cerebros spinal fluid which not only protects our brain but it also plays a crucial role in maintaining homeostasis among other critical functions certain gal cells are integral when it comes to our immune function within our nervous system honestly these examples are just scratching the surface of the diverse and essential roles that these gal cells play within our body last for neuro let's break down neuron input and output and how they play a crucial role in how our bodies function first up we have our afferent neurons also known as our Sensory neurons they carry signals towards the central nervous system from our sensory receptors I like to think of afferent as admission or afferent arrives because they admit information into the brain and spinal cord from the body so again using the example we talked about before when we touch a hot stove our sensory receptors in our skin are going to detect this extreme heat it's those afferent neurons that are going to quickly carry that information to our brain signaling that something is painfully hot now moving over to our eent neurons these are known as our motor neurons because they carry signals away from the central nervous system to muscles and glands I like to think of this as eperen exits because these types of neurons exit our brain and spinal cord to actually cause the action to take place so once our brain has processed the information received from our afferent neurons about the hot stove it needs to take action it's going to react it's these eent neurons that are going to carry the instructions from our our brain back to the muscles of our hand telling them to pull away this is the motor response that's initiated by our eent neurons so when it comes to the human digestive system we're going to explore the proficiency of Performing four essential functions we have ingestion digestion absorption and elimination starting with ingestion it's simply the intake of food as we move into digestion this involves the breakdown of large biomolecules recall that we have four major biomolecules that we discussed in our previous ait's videos these particular biomolecules are going to be broken down into their respective building blocks through mechanical and chemical means next as we move into absorption this is where those nutrients are going to be taken up by the body this process is crucial because it allows nutrients to be delivered to the cells supporting their survival function through cooperation with other bodily systems and then lastly we have elimination which deals with the expulsion of substances that were not digested clearing waste from our bodies so let's break these down even further so in humans ingestion begins when food enters our mouth if you think about it even the thought of food can actually make our mouth release saliva so when that food is brought into our mouth this is when that digestion process begins and that is when the saliva that contains enzymes are going to start to break down those biomolecules using things like salivary amase which starts to break down carbohydrates this enzymatic breakdown is known as chemical digestion alongside this we have mechanical digestion which occurs in our mouth mechanical digestion is the physical breakdown of food primarily accompanied by our teeth and they ultimately end up grinding that food into smaller pieces saliva is going to play a multiun functional and underappreciated role when it comes to chemical digestion not only does it contain digestive enzymes but it also includes buffers that are going to neutralize that acidity found inside of our mouth helping to protect our teeth against tooth decay additionally a lack of sufficient saliva is a condition known as dry mouth and this can also pose serious health risks when it comes to our Dental Health saliva not only AIDS in our digestion of food but it also lubricates it making it easier for your tongue to mold that food into a small ball known as a Bolis this Bolis of food is then going to be swallowed as it travels down our esophagus an ingenious feature when it comes to our body is known as the epig Lotus and this epig Lotus is going to act as a protective flap that's going to cover our wind pipes so that we don't have any food going down the wrong hole this is crucial because the trachea and the esophagus are located very very close to one another and this prevents that food from entering the tracha essentially avoiding us from choking on our food the process of peristalsis is then going to take place and what's Happening Here is there's a WAV likee muscle contraction of our smooth muscles in the esophagus efficiently moving that Bolis further downward as it heads towards our stomach so when we talk about the adult stomach the adult stomach actually has a capacity to hold approximately 2 lers of both food and liquid this environment is highly acidic facilitating chemical digestion through the stomach's gastric juice juices this includes our hydrochloric acid HCL and enzymes like pepsin that helps us break down proteins additionally mechanical digestion is also going to take place as the stomach is going to churn its muscles to help churn all of that contents found within it thoroughly mixing them with those gastric juices this process of that churning of the food is going to make it into a semi- liquid mixture known as Kim there's a couple of sphincters you're really going to need to be made aware of when it comes to the aits and that is our lower esophageal sphincter and our pyloric sphincter when it comes to our lower esophageal sphincter it is positioned at the junction where our esophagus ultimately meets our stomach this sphincter primary function is to open and allow food and liquids to enter the stomach and then close it tightly to prevent any of that acidic contents from the stomach reflexing back into our esophagus this ultimately helps prevent things like heartburn and gastro ESOP FAL reflex disease also known as gird on the other end of our stomach we have our pyloric sphincter and this valve is located between our stomach and our small intestine also known as the start of our dadum its main function is to control the passage of partially digested food into our small intestine this sphincter also helps prevent any backflow of intestinal contents into the stomach so let's move on to our small intestine this is the point when digestion ends and absorption Begins the dadum junam and ilium are the three contigous sections when it comes to our small intestine each of them playing a unique role when it comes to digestion and absorption these sections ultimately work together to ensure that nutrients are effectively absorbed into the body so we're going to start with our duum and this is ultimately the first and shortest segment of our small intestine it immediately follows our stomach its primary role is the chemical digestion of Kim facilitated by enzy from the pancreas as well as bile from the liver the Dum is crucial when it comes to the fats proteins and carbohydrates that need to be broken down it also absorbs iron and other minerals in this specific location and then next up we have the gunum which is the middle section of our small intestines and it's primarily responsible for the absorption of nutrients the walls of our gunum are lined with these kind of villi they're these little small finger-like projections that increase the surface area for absorption here most of the carbohydrates and proteins are going to be absorbed into the bloodstream and then last up we have our ilium which is the final segment of our small intestine and it's primarily responsible when it comes to absorbing vitamin B12 bile salts and whatever products of digestion were not absorbed by the junim the ilium is also going to play a crucial role when it comes to absorbing fat soluble vitamins like a d e and K an easy way I like to remember the order of the small intestines is digestive juices intake digestive Sans for aadum juices stands for our junim and intake completes it with our ilens signifying the completion of nutrient absorption next up we have the large intestine and this is an essential part of our digestive tract as it's comprised of several key segments we have our ascending colon our transverse colon and our descending colon starting with our ascending colon this is the first segment of our large intestine and it's located on the right side of our abdomen it begins at the seeum just below that ilocal valve and it receives digested material from the small intestine the primary function of the ascending colon is to absorb water and salt from the remaining digested material this absorption is going to help solidify that waist into a more formed stool next up we have our transverse colon and this is the longest most mobile part of our large intestine the transverse colon stretches across our abdomen from the right to the left it acts as the storage site for the remains of our digested food that was not previously absorbed in the small intestine in this segment further absorption of water and salts continue gradually turning that digestive material into a thicker more solid form as It prepares to enter our descending colon and then last up you guess it we have our descending colon which is located on the left side of our body the Des and colon carries the increasingly Solid Waste downwards towards our rectum it continues that process of water and mineral absorption further consolidating that waste before it's eventually expelled from the body this segment plays a crucial role in storing the feces until defecation and it's integral part of the body's waist management and excretion systems the biggest key takeaway I want you to remember when it comes to large intestines is it's the primary site for water absorption it's the most prevalent place where this takes place an easy way to remember this is ascending absorbs transverse transports and descending drives down this pneumonic ultimately helps encapsulate the primary functions of each segment ascending absorbs water and minerals are absorbed here transverse transports it acts as a conduit while continuing that absorption and descending drives down moves that Solid Waste further down before it gets eliminated then lastly we reach the concluding phase of our digestive system known as elimination and the rectum marks that final segment of our large intestine where feces are stored until they're ultimately expelled from the anus so throughout this talk we've noted organs such as the gallbladder liver and pancreas because they contribute digestive juices to that digestion process though they're referred to as accessory organs their role holes are far from secondary the liver is the largest internal organ not only does it perform various functions outside of digestion but within the digestive system it is crucial for the metabolism of carbohydrates and proteins it also produces bile which is essential for the breakdown of lipids and the gallbladder acts as a storage facility for the bile that the liver produces releasing it when it's needed for the process of digestion meanwhile the pain pus produces pancreatic juices that contain vital digestive enzymes that help neutralize that acidic kind playing a critical role when it comes to the digestive process and lastly we're going to talk about key players when it comes to hormones as well as enzymes that we're going to find in our digestive system these are a few that are going to be crucial for you to know when it comes to the aits first up we have gastrin and gastrin is found in the G cells within our stomach lining their primary function is to help with stimulating gastric glands to secrete pepsinogen it's a precursor for pepsin like we talked about before and hydrochloric acid which is going to Aid in the digestion of proteins it's ultimately going to be released when we eat foods that are high in proteins next up we have choic cystic which are going to be found in the eye cells of our mucus Linings within our duum and our gunum its primary function is to digest fats as well as proteins it's going to stimulate that gall bladder to release and contract all of that stored bile that it has into the intestines cck also prompts the pancreas to secrete its digestive enzymes which are necessary for breaking down proteins carbohydrates and the fats that you find in Kim next up we have secretin which are found in the S cells of our dadum saine's primary role is to regulate the pH balance in the dadum by inhib in gastric acid secretions from the stomach and stimulating the production of bicarbonate from our pancreas bicarbonate is going to help neutralize that acidic kind that enters that small intestine from the stomach next up we have insulin and insulin is found in the beta cells of our pancreas insulin plays a crucial role when it comes to glucose metabolism it's going to facilitate the uptake of glucose by the cells thus lowering our blood sugar levels insulin is also going to stimulate the liver and our muscle cells to store glucose as glycogen and it promotes the synthesis of fats in our adapost tissue then we have glucagon which is found in the alpha cells of our pancreas glucagon is going to do the complete opposite of what insulin does and it's going to work to raise our blood glucose levels it does this by stimulating the liver to break down that stored glycogen into glucose and then that glucose is going to be released into our bloodstream this hormone is essential for maintaining fuel balance and is especially active between meals and during exercise and then last up we have our bile which is produced by our liver and ultimately stored in our gallbladder bile itself does not break down substances but It ultimately emulsifies fats making them more accessible to the digestive enzymes that digest lipids this action is crucial for the efficient digestion and absorb of fatty substances in the small intestine the good thing to know is that the aits is not going to delve into the names of various muscles but it is going to focus more on muscle tissue and the mechanism of muscle contraction particularly when it comes to that actin mein cycle first up let's discuss muscle tissue so muscle tissue consists of muscle fibers which are essential when it comes to muscle cells these fibers have specialized structures that enhance their functionality we're going to cover three types of muscle tissue cardiac muscle smooth muscle and skeletal muscle so starting with cardiac muscle tissue it's as the name implies it's primarily found in our heart these fibers are going to have this branched like appearance and they're going to be striped or striated as well cardiac muscle is going to have this striated appearance due to its presence of sacir which are the basic structural and functional unit when it comes to muscle fibers we're going to be discussing this concept a little bit more into detail in just a moment each fiber is going to contain a single nucleus and at the end of these fibers you're going to see these interc calculated discs which are there to provide a organized wav likee pattern this organized Arrangement allows for efficient coordinated contractions which are essential for pumping blood throughout our body what's important to know is that control of this muscle tissue is involuntary meaning that it operates without our conscious control next up we have smooth muscle tissue which is characterized as a non-striated uniform appearance hence the name smooth unlike striated muscle it lacks visible stripes or bands each muscle fiber has this kind of spindle shape featuring a more broader Center as it tapers off down towards the ends and it also contains a single nucleus smooth muscle is found throughout the body including our digestive system in the walls of Our arteries and our veins in the bladder as well as in our eyes where it adjust the size of our Iris like cardiac muscle smooth muscle also operates involuntarily meaning that it functions not under conscious control it allows it to handle essential bodily functions automatically and lastly we have skeletal muscle tissue which is what typically comes to mind whenever you think of your bicep or your tricep this type of muscle attaches to to both our bones and our skin and this one is actually under voluntary control meaning that we can consciously operate it for instance anytime I think about wanting to pick something up I'm able to consciously control picking that item up this is what we mean by that voluntary control if we were to look closely at these kinds of muscles you're going to find that skeletal muscle tissue fibers are going to be striated displaying that same striation appearance like we saw with our cardiac muscles the fibers themselves are going to be long and cylinder and each one of these fibers is going to have multiple nuclei this is very different from what we talked about when it came to cardiac and smooth muscle this kind of unique structure is going to be crucial for their function when it comes to Rapid and forceful contraction over an extended period of time all muscle tissues share several key characteristics worth noting they possess extensibility meaning that they can stretch or extend and then they have elas elasticity meaning that they can return back to their original form after they were stretched muscle tissue can also exhibit excitability which refers to the cell's ability to respond to stimuli in muscle tissues this trait allows their membranes to undergo electrical changes and transmit Action potentials additionally muscle tissues are capable of Contracting a property known as contractility the mechanism of contraction varies among the three different kinds of muscle tis tissues if we delve into cellular structures of skeletal muscle we can explore how it accomplishes its primary function contraction it is arguably the most fascinating aspect of this discussion let's take for example our bicep muscle this muscle is composed of numerous muscle fibers which are essentially muscle cells within each muscle fiber you're going to find multiple myop virals which are elongated cylinders these myop virals are segmented into repeating units known as sacir the specific arrangement of these sacir gives skeletal muscles its distinctive striad appearance within each sacr Mir you're going to find the protein actin which forms what is known as our thin filaments there's an additional protein known as mein which constitutes our thick filaments to help you remember which one is which think of the word thin being nearly contained in the word actin it's just ultimately missing that H but it closely AIDS in helping us remember the differences between our thin and our thick filaments both actin and mein are vital when it comes to muscle contraction as they both play a key role in that mechanic so let's talk about the sliding filament model when it comes to muscle contraction I'm going to provide a simplified explanation of this concept but know that it could go way further into detail so let's start with the basic components which we already know about our sacr we have our actin which is our thin filaments which is going to be here in our brown color and we have mein which is our thick filaments which are going to be here in our blue color the sacr mirror is bound at each end by Z lines like we see here in yellow where thin filaments are ultimately going to attach which is our actin on the other hand our thick filaments which is our mein is going to attach to the center line known as our mline through accessory proteins a crucial aspect when it comes to muscle contraction is the shortening of our s acir however it's really important to note that the thick and thin filaments do not actively shorten themselves instead what's actually going to happen is they're going to slide past each other facilitating this process during this contraction our thin filaments are going to be pulled towards the center of our sacr Mirror by our thick filaments causing that zline to ultimately move closer together and the filaments are going to overlap each other more extensively so it's really critical to know when you're Tak making your atits is that the thick and thin filaments do not shorten they just ultimately slide if we were to further zoom into this process this is what it's going to look like on a molecular level on the thin filament we have our actin which we see here in brown and on our thick filament we have our mein which we see here in blue our mein are equipped with these mein heads although there are hundreds of these heads we're going to focus on just one to provide us with more clarity this mein head that we have right here is going to bind to ATP it's going to become hydrolized and turn into a DP and a phosphate group both of which remain on that mein head this process is going to enable those mein heads to bind to that actin forming what we know as a crossbridge subsequently that mein head is going to release that ADP in that phosphate group and it's going to undergo this kind of bending motion known as a power stroke as it drags that thin filament towards the center of the sacr Mir a new ATP is then going to bind again to that mein head and that's going to allow that head to detach from the actum this necessity for ATP is also why muscles become rigid after death in a state known as riam mortis without this ATP the mein heads don't know whether they can detach from the actin during muscle contraction imagine hundreds of these crossbridge formations continuously forming and breaking as each mein head performs its power strokes this action with some of the heads always attached to the actin prevents those thin filaments from slipping back into their original positions ensuring that we have an effective muscle contraction so what is the reproductive system this system encompasses the primary internal reproductive organs known as the gonads which are our testes and our ovaries they produce various sex hormones and gtes including sperm and eggs additionally it involves glands ducts external genitalia and specific areas of the brain that support the functions of the gonads and the gametes the whole foundational purpose of these components is to facilitate mating the combination of genetic material and reproduction for our life and physical science series you might remember that gametes are haploid cells produced through meiosis unlike the rest of the body's diploid cells that result from mitosis we've discussed this process extensively in that video so please feel free to revisit the teas Life and Science comprehensive review but to summarize in human reproduction males produce sperm cells and females produce egg cells both are a different type of gamt when these gametes unite during sexual intercourse the process of fertilization occurs this Fusion forms a zygote which embarks on a journey of embryonic development eventually leading to the birth of a new human being given that the reproductive system of males and females exhibit significant differences it's most effective to study them independently let's begin by exploring the male reproductive system as we previously mentioned the primary reproductive organ in males is the testes which produce testosterone the testes epidemis and the lower part of the sportic cord are located within a skin pouch known as the scrotum this pouch is separated into two compartments by a central divider called the septum the tessis is also the site of sperm production although it might seem risky to store these vital cells in an external sack the slightly cooler temperatures outside the body provides the optimal conditions for sperm development each testy is encased in two layers the inner Tunica alagen and the outer layer the Tunica vaginalis internally the tessis are seged into lobules and these lobules house tightly coiled seminiferous tubules sperm production from spermatogenic cells occur inside of these tubules through a process known as spermatogenesis these semine neous tubules eventually merge into a straight tubule that's going to lead to our re test from that re tesus sperm is going to travel up through a network of ducks until it reaches that epidemis this is where sperm are stored and mature until they're expelled during ejaculation when ejaculation occurs sperm cells are going to travel up our vast defrin and it's going to go into our Jacory duct eventually it's going to enter into the urethra which is the final channel for urine in the urinary system this route enables sperm to exit the body through the penis which is a copulatory organ designed to deliver sperm into the female reproductive tract along with the scrotum the penis forms the external genitalia of the male in addition to the gonads and external genitalia the male reproductive system includes accessory glands such as the seal glands the prostate and the Buble urethal gland seminal vesicles are glands that are located on the surface of the bladder and secrete a fluid known as semen it's really important to note that seen does not contain sperm cells instead it mixes with sperm cells during ejaculation in the ejaculatory duct sperm plays a crucial role in enhancing sperm motility and fertilizing ability by providing a nutrient-rich medium that suppresses the immune response in the female reproductive tract It ultimately destroys bacteria and AIDS sperm in adhering to the walls of the vagina to prevent drainage Sean comprises the bulk of the ejaculate by volume next up we have the prostate gland and the prostate gland is positioned around the urethra near the bladder the prostate function is to contract during ejaculation pushing the secretions into the urethra to mix with the ejaculate these secretions help activate the sperm to increase fertility and lastly we have our Buble urethal glands and they're located near the prostate these glands produce mucus that are going to lubricate the gland's penis which is the tip of the penis during sexual AR Razzle facilitating smoother penetration and enhancing sexual intercourse Comfort next up let's explore the female reproduction system which involves a more complex Arrangement starting off with the female gonads known as the ovaries they are responsible for producing the female gami or egg cells known as OVA along with sex hormones estrogen and progesterone ovaries function similarly like we see with the tessis but they're located inside the body each ovary is encased in a fibrous layer known as the tuna alagen just like we saw with the tesses and it's also covered with a layer of germinal epithelium they are anchored in place by various ligaments and receive blood supply from the ovarian arteries within the cortex there are numerous follicles each containing an immature egg known as an oite this process of maturing an egg cell is known as oogenesis as development progresses a primordial follicle is going to mature into a vesicular follicle characterized by a fluid filled cavity like you can see right here known as the Anum eventually this mature follicle is going to protrude from the ovary surface where it is going to be released during ovulation into the fallopian tubes for potential fertilization after ovulation that released oite is going to release into our Fallopian tubes fertilization typically occurs within the phop I opian tubes before the egg continues its Journey down into our uterus commonly referred to as the womb in the uterus the fertilized egg is going to embed itself into the uterine wall where it remains and develops throughout the pregnancy the cervical Canal is going to lead down into the vagina which is the female catatory organ the vagina is designed to receive the penis during sexual intercourse and also serves as the passageway for child birth in anatomical females the external genitalia area is known as the vulva and it comprises of several distinct Parts first up we have the mons pubis and this is the fatty area that sits above the pelvic bone providing cushion and protection it also becomes covered with pubic hair after a female reaches puberty and then in blue we have the labia majora which is the outer larger skin folds that protect the internal structures of the vulva this area is also covered with pubic hair and it contains sweat and oil secreting glands inside of our labia majora we have the labia manora here in pink these are the thinner inner folds of the skin that are hairless and encase the most delicate areas of the vulva and then we have the vestibule and this is nestled in our labia manora this area houses the openings of our urethra as well as our vagina so the urethra Orphus is located right here above the vaginal orice and this is the opening where the urine is going to be expelled from the body and then we have the vaginal orice is situated right here it's right below our urethal orice and it's the opening that serves as several key reproductive functions this includes the passage of menstrual blood a receptor site for sperm and as part of the birth canal during labor and then lastly we have the anus although it's not part of the vulvo the anus is located posterior to the vaginal Orphus and is the exit point for feal matter from the body each one of these components are crucial for the reproductive and excretory functions of the female body as well as providing protection against external irritants and infections the endocrine system and reproductive system are intricately linked through the action of hormones which regulate both the development and function of the reproductive organs hormones like estrogen testosterone and progesterone play a critical role in sexual reproduction fertility and pregnancy in the brain the hypothalmus patory region acts as a Central Command over seing the endocrine system the pituitary gland is divided into two parts we have the anterior which is in the front and the posterior which is in the back both of them Branch off from our hypothalamus the hypothalmus produces several hormones which the posterior pituitary gland stores and later releases unlike its counterpart the posterior pituitary gland does not produce its own hormones instead it secretes hormones like oxytocin which is crucial for uterine contractions during childbirth the anterior pituitary gland however is a hormone powerhouse it's capable of producing its own hormones while still being tightly regulated by that Halo thalmus some of its key hormones when it comes to the reproductive system include prolactin which stimulates milk production in the mamory glands and there's also the follicle stimulating hormone which stimulates the formation of the OVA and sperm and then last up we have the lutenizing hormone which produces ovulation and androgens respectively and lastly as we discussed the gonads are going to produce several important hormones the ovaries produce estrogen which primarily promotes the growth of the uterine lining and the development of female secondary sex characteristics Additionally the ovaries produce progesterone which not only supports but also maintains our uterine lining growth and plays a vital role in fetal development during pregnancy the testes produce androgens such as things like testosterone which are essential for sperm production and the development of male secondary sex characteristics it's important to note that while estrogen progesterone and testosterone are present in all individuals these hormon hormone concentrations and primary functions vary typically estrogen and progesterone are found in higher levels and play more significant roles in females whereas androgens like testosterone are more concentrated and predominantly function in males let's talk about the skin being the largest organ it's quite appropriate that it belongs to a system with such an extensive name the integumentary system but you might be asking yourself why is the skin so important when you think about it there's actually several reasons why it plays a crucial role in maintaining homeostasis by regulating our internal body temperature as well as fluid balance the skin can also act as a physical barrier protecting internal structures and organs from damage it guards against invasion of pathogens like bacteria and viruses and it's the site where vitamin D synthesis occurs skin also possesses sensory function so for example if a worm was to touch your foot you would typically be aware of its presence and if you're like me you would be going running and screaming in the other direction the integumentary system is layered featuring various tissues as well as different cell types let's begin by breaking each one of these layers down let's start by discussing a type of cell found throughout the epidermis known as keratinocytes keratin aides produce keratin which is a protein that enhances the water resistance and toughness of of our cells these types of cells originate down here in the bottom of our epidermis and they slowly push their way up towards the top known as our superficial layer where they undergo a process known as cornification cornified cells hence the name of our most superficial layer stratum corneum means that these cells are hardened flooded and they are tough at this stage within our epidermis they are dead which means that they've lost the organel and they're filled up with that keratin instead before we delve deeper into the layers of the epidermis it would be useful to have a pneumonic to help us remember the sequence at which these layers occur from the outermost to the innermost here's a neonic that I like to use it's called come let's get sunburned the first letter of each word stands for each letter of our epidermal layers starting at the top of our epidermis we have the stratum corneum and this layer is composed of those cornified cells those dead cells that are continuously being sloft off so that new cells can arise from the layers below to replace them just below that later is the stratum lucidium and this is where you're going to find that more thick skinned areas you're going to find a lot with the soles of your feet as well as the palm of your hands this layer also consists of cornified cells which is a protein that gives them this transparent layer appearance hence the name lucidium next up we have the stratum granulosum and here those keratinocytes push push up from those lower layers and they begin to flatten out and begin to accumulate granules as suggested by the layer's name these granules perform various functions including forming a water protective layer for the skin those carattino sites in this layer will eventually lose their organel and then they're going to transform into those more cornified cells in the upper layers moving deeper we have the stratum spinosum which contains several layers of those carao sites but it also has its a particular type of cell called the langerhan cell these langerhan cells that are found in this layer work similar to that of a microf fodge consuming up worn out cells and bacteria what's interesting is that the name of this layer comes from its appearance when you look at it under a microscope it looks kind of spiny when it's stained the deepest layer of the epidermis is called the stratum Basile it consists of a single layer of Basil cells which are constantly undergoing mitosis to produce new cartino sites which are then going to migrate upwards to the more higher levels if you have thick skin on maybe your feet or even maybe a callus on your palm it's likely due to the stratum Basile layer it responds to those frequent abrasions by producing more cells thereby thickening that stratum corneum above it additionally the stratum basil is going to contain melanocytes which produce melanin that's a pigment that contributes to the skin color and Prov provides protection against UV radiation the melanin is transferred to keratinocytes in structures called melanoses another type of cell that can be found here are Merkel cells whose precise function is still under study but it's believed that they're involved in the nervous system particularly enhancing our sense of touch the stratum Basile is the deepest layer of our epidermis and it's tightly connected to the dermis which we're going to explore next unlike the epiderm the dermis contains blood vessels it is also composed of connective tissue a type of tissue distinct from that epidermal layer that serves to bind structures together within our body you can think of the dermis as kind of like the glue that connects everything together within the dermis you can also find things like sweat glands nerves as well as hair follicles which are all integral to the Skin's function this layer is also reinforced with fibers and there's two key types of proteins we have collagen and we have elastin collagen provides more of a structural support and elastin grants us our elasticity these particular proteins are produced by specialized cells known as fibroblasts which are located throughout the dermis the dermis is divided into two primary layers we have the papillary layer which consists of looser connective tissue and we have the reticular layer beneath it which is the connective tissue that's more densely packed together before we move on to the hypodermis it's pertinent that we take a moment to discuss scars when we have more superficial cuts it will only affect the epidermis generally not leaving a scar behind however deeper cuts that do reach that dermis often result in scarring these scars are typically going to appear distinct from the surrounding tissue because their formation process is going to differ from the original skin structure this difference arises because during healing fibroblast produced collagen but they do not align in the same pattern that they were originally present additionally features like sweat glands and hair follicles which we're going to discuss a little bit later are not regenerated in that scar tissue consequently scar tissues usually have reduced elasticity which means extensive scars with those much more larger wounds can eventually impact mobility in some cases we may see keloids which are regular fibrous tissues formed at the S of a scar due to increased collagen production now we're going to proceed to our final layer which is the hypodermis also known as the subcutaneous tissue layer positioned beneath the dermis that hypodermis is a connective layer that links the skin to the underlying bone and muscle tissue what's important to note is that the hypodermis is primarily composed of adapost tissue which is essentially stored body fat this layer plays a crucial role when it comes to providing the body with insulation now that we've explored the layers of the skin let's discuss some accessory structures that we haven't yet covered such as our sweat glands sweat glands play a critical role when it comes to cooling the body through persperation which is just a fancy way of saying sweating however sweat glands are not the only method that the skin uses to regulate temperature blood vessels in our dermis can actually dilate or widen allowing heat to escape through the skin conversely in cold temperatures where we need to maintain our heat our blood vessels can actually constrict and draw that heat away from the surface so that we can conserve it inside the body another key accessory structure is our sebaceous glands these glands produce oil that's going to help waterproof and lubricate our skin as well as our hair this oil production is vital in maintaining the health of our skin and the moisture of the cartino sites we discussed earlier hair follicles if you recall are found within the dermis layer of our Skin Within These hair follicles more specifically at the base of our hair bulb cells are going to rapidly undergo mitosis as these cells continuously multiply they're going to push outward driving the growth of the hair root the visible part of our hair known as our hair shaft is composed of keratin and is non-living so when we talk about Nails Nails originate from our epidermis specifically from the base known as a nail root just like we saw with hair follicles this area is going to contain cells that are actively undergoing mitosis as these cells continuously multiply they are again going to push outward which contributes to the growth of our nails the visible part of our nail known as the nail body serves to protect the tips of our fingers and toes and is composed of those dead karatinos sites as with all of our videos I always like to emphasize the importance of understanding the why why is it essential that we learn about the integumentary system a key reason for this is the prevalence of skin cancer skin cancer is the most common cancer in the United States current estimates that it's about one in five Americans will develop skin cancer in their life time and it's also estimated that approximately 9500 people in the United States are going to be diagnosed with skin cancer every single day skin cancer can develop when the cells of the integumentary system begin to malfunction and divide uncontrollably so for example the basil cells in our epidermis can develop into basil cell carcinoma it's the most common frequent type of skin cancer found in humans similarly melanocytes the cells responsible for producing our melanin can also become cancerous and lead to melanoma a more aggressive type of skin cancer squamous cell carcinoma is a common type of skin cancer that arises from the squamous cells which are are those flat thin cells that make up the outermost layer of our epidermis this form of cancer is primarily caused by the prolonged exposure of ultraviolet radiation either from sunlight or even from tanning beds leading to the DNA damage of our skin cells and lastly we're going to discuss Burns and in this particular situation the Skin's function is going to be severely compromised burns are typically categorized into degrees based on the depth of the skin that it has damaged Burns can be classified into four main classifications we have first deegree Burns which affects our epidermis we have second degree burns which extends into the epidermis and the upper layers of our dermis we have third degree burns which is going to penetrate down into the depths of our epidermis and our dermis and then lastly we have fourth degree burns which is going to go all the way down to damage those deeper tissues potentially even affecting muscle muscles and Bones interestingly enough when we have third and fourth degree burns they can actually cause less pain than those milder Burns that we see more superficially due to nerve damage taking place significant Burns pose serious risks when it comes to impairing the Skin's essential functions such as things like fluid retention or even protection against those external threats and lastly the damaged skin is highly susceptible when it comes to infection so we have to make sure that we address this promptly to prevent any other complications from taking place the endocrine system is composed of various structures that release hormones which can occur at the individual cell level or the entire organ so starting at the top when it comes to our brain we have the hypothalamus the pineal gland and the pituitary gland moving down to our neck we have the thyroid gland and the parathyroid gland further down into our chest we have the thus gland positioned right above our kidneys we have the adrenal gland and right next to our stomach we have the pancreas and then lastly we have our gonads which are the reproductive glands we can have ovaries and females and we have testes and males so let's highlight two key points when we discuss these different kinds of glands firstly our Focus here is going to be primarily on the endocrine function of these glands not the exocrine function so what's the difference endocrine glands release hormones directly into their surrounding environment like blood vessels without the need of actually having to have Ducks conversely exocrine glands have to have ducts in order to transport those secretions to the body's surfaces and Cavities think of things like sweat glands mamory glands which produce milk these kind of glands are exocrine glands there's a great memory trick when it comes to remembering the differences between these two types of glands when it comes to endocrine I like to think of the en and endocrine and the en and enter which means that endocrine glands secrete hormones directly into the bloodstream they enter their internal environment whereas the ex and exocrine and the ex in exit lets us know that exocrine glands use ducts to transport these secretions out of the gland and either onto the surface of our body or our body cavities what's really interesting is that some glands like we see with our pancreas have both endocrine and exine functions for example its endocrine activity involves releasing insulin and glucagon to manage blood sugar levels while its exocrine function involves secreting digestive enzymes through ducts into the small intestine and secondly while we've covered major endocrine glands it's important to recognize that endocrine functions can also be found in cells within other organs let's take the stomach for example in our discussion about the digestive system we discussed that enzymes and hydrochloric acid in gastric juices but we never mentioned gastrin which is a hormone that facilitates the secretion of stomach acid gastron is produced by specific cells found within our stomach showing how widespread endocrine activities can be found throughout the body let's move on to the role of hormones it's important to understand that hormones can come from various biomolecules some of these can be derived from amino acids or chains of amino acids known as polypeptides and some may be derived from lipids such as steroids the composition of a hormone significantly impacts its function including the specific receptor sites that are going to bind to targeted cells once bound hormones are going to trigger these cells to perform specific actions such as accelerating mitosis or activating certain enzymes given the diverse responses of targeted cells we'll revisit the glands and explore some of the major hormones associated with each one outlining their General functions this will give us a clear picture of how hormones influence bodily processes so starting in the brain the hypothalamus pituitary region acts as a Central Command overseeing much of the endocrine system the pituitary gland is divided into two parts we have the interior pituitary which is more towards the front and the posterior pituitary which is more towards the back both of which branch off from the hypothalamus the hypo thus produces several hormones which the posterior pituitary stores in later releases what's really cool is that unlike its counterpart our posterior pituitary does not produce its own hormones instead it secretes hormones like oxytocin which is crucial for uterine contractions during child birth an anti-diuretic hormone also known as ADH which promotes the kidneys to reabsorb water the anterior pituitary however is a hormone power powerhouse it's capable of producing its own hormones while still being tightly regulated by the hypothalmus some of the key hormones you're going to see is growth hormone which you might have guessed promotes growth prolactin also known as PRL stimulates milk production in the mamory glands thyroid stimulating hormone which activates the thyroid to release thyroid hormones follicle stimulating hormone which stimulates the formation of the OVA and sperm lutenizing hormone produces ovulation and androgens respectfully and lastly we have the andreno corticotropic hormone also known as act which drives the adrenal cortex to release various hormones like cortisol here's some easy ways to help you remember these different kinds of hormones remember oxytocin when it comes to obstetrics as this helps with the uterine contractions during childbirth when you think of ADH think of the D as you can't pee as this helps the body retain water by preventing diuresis also known as urination when it comes to growth hormone I like to think of GH standing for grow high as it focuses on promoting body growth the PRL when it comes to prolactin stands for produce real lactation cuz it stimulates milk production the TSH and thyroid stimulating hormone stands for thyroid secretion helper as it stimulates the thyroid to release thyroid hormones the FSH and follicle stimulating hormone stands for a follicle selection hormone since it stimulates the gonads to produce gametes the LH in lutenizing hormone stands for ltil phase hormone because it plays a critical role in menstration and ovulation and then lastly the ACT stands for adrenal cortex triggering hormone because it stimulates the adrenal cortex to release various hormones it's important not to overlook the small yet mighty pineal gland despite its size it plays a significant role by secreting melatonin which is key in regulating our circadian rhythm that's the natural cycle that influences our sleep wake cycle next up we have the thyroid gland which is that butterfly shaped gland that Nestles beneath the larynx and encircles the trachea in the front this gland produces T4 and T3 hormones which are pivotal in regulating metabolic processes additionally the thyroid gland secretes calcitonin which is a hormone that helps reduce our blood calcium levels the parathyroid gland is located at the back or posterior position relative to the thyroid gland and this particular gland is going to secrete something known as parathyroid hormone which plays a critical role in increasing our blood calcium levels so why is calcium so important calcium plays a vital role in nerve transmission and muscle function including the proper functioning of the heart muscle it's also essential when it comes to blood clotting processes and helps regulate enzyme activity and hormone secretion there are some easy ways to remember the functions of T4 T3 calcitonin and parathyroid hormone I like to think of the T and T4 and T3 as standing for thyroid and the numbers four and three indicate the number of ion molecules each contains both of these hormones are crucial for turning up the body's metabolic rate like turning up the heat to make things go faster when it comes to calcitonin I like to remember it as caleton it down because it helps lower the levels of calcium that are found in our blood when they're too high and with parathyroid hormone you can think of it as parathyroid pushes it up meaning that it's going to increase those calcium levels in our blood when we don't have enough so next let's focus on AR thymus gland what's interesting is that some endocrine diagrams might leave out the thymus possibly because it diminishes inside as a person matures into adulthood however as a gland the thymus produces hormones that influence immune function also known as thymosin thymosin is particularly important because it stimulates the production of our tea cells which are key players in the immune response an easy way to remember thymosin is thy must stimulate immunity this pneumonic helps link thymosin in its crucial role when it comes to our immune system system next up let's examine the adrenal glands which are situated right here above our kidney these glands are comprised of two distinct parts we have the Adrenal medulla and the adrenal cortex the Adrenal medulla secretes two things it secretes epinephrine and nor epinephrine which are hormones that are crucial for initiating the fight ORF flight response that we see in our body during stress epinephine primarily influences the heart while nor epinephine Works primarily on our blood vessels I like to remember this with a pneumonic Epi no rush meaning that Epi stands for epinephrine no stands for norepinephrine as it's essential for it to rush or burst out of energy needed for that fight ORF flight response moving on to the adrenal cortex it produces something known as glyco cortic or steroids with cortisol being its primary example cortisol helps increase blood glucose levels and plays significant roles in managing stress and reducing inflammation Additionally the adrenal cortex secretes mineral corticosteroids such as aldosterone which is essential for balancing electrolytes in the body elderone for example helps regulate sodium reabsorption and pottassium excretion in the nephrons of the kidney some tips and ways that I like to remember these is that cortisol controls stress because it helps manage stress and inflammation and for adrone I like to think of Aldo stor na or the Aldo stands for aldosterone because it stores sodium which is our na inside of our body next up the pancreas plays a crucial role in managing the body's glucose levels after we eat glucose which is a type of sugar enters our bloodstream insulin which is a hormone produced by our pancreas is going to Signal the body's cells to absorb the glucose without insulin cells cannot access glucose they need for energy which is why many individuals with diabetes may need to take insulin injections if their pancreas isn't functioning appropriately Additionally the pancreas produces glycon another important hormone that helps increase blood glucose levels by promoting the liver to convert its stored glycogen into glucose ensuring that the body maintains a balanced energy Supply with insulin think insulin puts sugar in insulin is key when it comes to letting glucose enter the cell this pneumonic emphasizes that insulin's primary role to lower blood sugar levels by facilitating glucose entry into the cells and with glucagon I want you to think of glucagon raises glucose remember glucagon is the hormone that gets glucose going by raising blood sugar levels and of course as we know it does this by signaling the liver to release glucose into the bloodstream and then lastly we're going to discuss our goads that is our ovaries and our testes the ovaries produce estrogen which primarily promotes the growth of the uterine lining and the development of female secondary sex characteristics Additionally the ovaries produce progesterone which not only supports but also maintains that uterine lining growth and helps play a prival role in fetal development during pregnancy on the other hand testies produce androgens also known as testosterone which is essential for sperm production and the development of male secondary sex characteristics it's important to note that while estrogen progesterone and testosterone are present in all individuals these hormone concentrations and primary functions are going to vary typically estrogen and progesterone are found in higher levels and play more significant roles in females whereas androgens like testosterone are more concentrated and predominantly function in males let's begin by tackling two crucial survival challenges first we need to maintain osmotic pressure this is essential because it involves the regulation of water and solute levels found throughout our body secondly the body must elimate metabolic waste metabolic waste can include things like carbon dioxide and nitrogenous waste which are byproducts of protein breakdown a frequent occurrence in metabolic processes the urinary system is designed to address these two critical issues with various organs and structures contributing to its function the skin for instance plays a role in excreting water and other substances the liver is heavily involved in detoxification and produces Ura and the lungs are responsible for expelling carbon dioxide gas it's important to remember that these organs also participate in other body systems the skin is part of the integumentary system the liver assists with digestion and the lungs are crucial when it comes to the respiratory system our primary focus today is going to be on the kidneys which are a key player when it comes to the urinary system but just know that all these systems work concurrently in order to help Tain these survival balances the urinary system is made up of a couple different kinds of organs we start off with the kidneys up here at the top which are just like kidney shaped beans that hold all of our urine and helps process all of those metabolic wastes they go down to the uers that ultimately lead down to our bladder where the urine is stored and then ultimately to the urethra where the urine is going to be expelled so when we talk about urine production this is primarily occurring in the kidneys each kidney contains approximately 1 million nephrons which are the fundamental working units of the kidney the primary function of our nefron is to filter waste products from the blood and convert it into urine we're going to start our exploration of the Nephron when it comes to the glome marialis which is a specialized cluster of capillaries this cluster is going to be encased in in our Bowman's capsule here blood pressure is going to push that fluid from the blood into the glus into the Bowman's capsule initiating what we call the filtration process once the fluid enters the Bowman capsule it is referred to as filtrate but what exactly does filtrate mean filtrate is a fluid that's going to contain several key components you're going to see things like water glucose amino acids and various different kinds of salts addition you're going to see things like hydrogen ions bicarbonate ions and other miscellaneous ions if present medications as well as some vitamins may also be found in our filtrate and it's also going to contain things like Ura which is a nitrogenous waste product generated by our liver that the body needs to eliminate the nefron subjects that filtrate to an intensive processing Journey as the filtrate moves through that nefron some of that is going to be re absorbed which means that specific filtrate components are going to cross back from the nephron into the surrounding interstitial fluid and then are going to be recirculated throughout the body however specific components are going to be retained in the nefron tubules to be eliminated as waste materials and eventually they're going to be excreted as urine renal secretion refers to the process of either passive or active transport of substances from the blood into the renal tubio where they will eventually be excreted as urine this is basically the opposite of reabsorption substances might move in and out of the nefron passively or they may undergo facilitated diffusion processes that do not require ATP also known as passive transport these types of transports operate along a concentration gradient where solutes or fluids are going to move from higher concentrations to lower concentrations occasionally some substances will need to go through the process of active transport where they are going to require ATP typically you're going to see substances moving from a lower concentration to a higher concentration while we aren't delving deeply into the specific types of transports when it comes to this video you can rewatch them through the chemistry portion of our ait's videos now that we understand these Concepts let's dive deeper into our nefron from our Bowman's capsule we're going to move into our proximal convoluted tubio proximal means near indicating that this tubal is closest to our glomerulus which is significant because there's another tubal further along and the proximal tubal salt is going to be transported into our interstitial fluid as you may know water follows salt by osmosis which is to be expected since that interstitial fluid becomes hypertonic due to that salt moving out into our interstitial fluid thus we typically say that salt and water are going to be reabsorbed because they're leaving the nefron and moving into that fluid other substances like glucose amino acids potassium as well as bicarbon also going to be reabsorbed here meaning that they are going to leave that proximal convoluted tubal and be transported into that interstitial fluid either through active or passive transport when we discuss reabsorption it's really important to note that not all substances are going to be fully reabsorbed some of these substances even though they're being reabsorbed in this particular area are still going to remain in that filtrate inside that proximal convoluted tubal secretion refers to substances moving from the fluid outside of the tubal to inside our proximal convoluted tubal so in this case you're going to see certain things being secreted like hydrogen ions and ammonium with certain substances being reabsorbed and others being secreted such as like we see with our bicarbonate and our hydrogen it's clear that the proximal convoluted tubo plays a crucial role when it comes to regulating our body's pH next up let's explore our Loop of Henley which consists of a descending limb that moves downward and an ascending limb which moves upward we're going to begin by discussing our descending Limb and this contains numerous aquap porns that are going to be found here these are special channels that facilitate the easy passage of water here water is going to be reabsorbed into our interstitial fluid which at this point we know is hypertonic because we have a higher concentration of solutes found inside of this area versus what's found in the filtrate inside of the loop of Henley as we discussed water is going to move osmotically towards that hypertonic area following that gradient solute concentration what's also interesting is that the descending Loop of Henley does not have channels for most salt use such as salt like we talked about before so all that salt that's still remaining within our Loop is going to remain here inside this portion of the nefron as the water is continuously exiting outside the descending Loop of Henley and as we continue to move further down this Loop you're going to find that the concentration of solutes found within our filtrate is going to increase so what exactly does that mean that means that we're going to see a lot more salts in this area without a whole lot of water so as we transition to that ascending Loop of Henley you're going to find that there's no aquaporin here so that remaining water is going to remain in our filtrates however in this segment you're going to find that there are specific proteins that are going to allow this salt to exit this particular section in the thin segment of our ascending Loop salt is going to move from that higher concentration within the filtrate to the lower concentration in our interstitial fluid so as we move upward into this thicker segment of our ascending Loop of Henley we're going to see a mass Exodus of salt as it continues to move from the filtrate into our interstitial fluid this is done through active Transportation further reducing that solute concentration within our filtrate and making this section more dilute as the filtrate loses more salt you can see that it becomes less concentrated by the time that it reaches the top of our ascending limb now we've moved on to our distal convoluted tubio substances like hydrogen pottassium and ammonium are going to be secreted into the filtrate with this particular section meanwhile our salts water and more bicarbonate are going to be reabsorbed from the filtrate back into that interstitial fluid the distal tubal plays a crucial role again in PH regulation by readjusting the secretion and reabsorption of these substances and then lastly we reach our collecting where the transformation of filtrate becomes urine in this phase salt continues to be reabsorbed water is also reabsorbed here as well but is really tightly controlled by hormones which are going to regulate the volume of water that is needed to be reabsorbed based on what the body needs so like we discussed hormones are going to regulate the water permeability within those collecting ducts which is crucial for maintaining body hydration for instance if you have a dehydrated person the collecting duck is going to kick in and reabsorb as much water as possible back into the interstitial fluid this is going to result in a more concentrated urine because you have less water conversely someone who has consumed a lot of water means that they are overhydrated so the body is going to be less reactive to reabsorbing water back into that interstitial fluid leading to a less concentrated urine because there's a lot more water we've also discussed previously how Ura is reabsorbed and secreted at various points in the nefron in the collecting duct a significant amount of Ura is going to remain in the filtrates however due to its high concentration some Ura is going to diffuse back into the interstitial fluid and as we finish our journey when it comes to urine production and expulsion through the body we know that urine that's produced by the kidneys are going to move down here into our uers where it's ultimately going to be stored on our bladder and then it's eventually excreted through our urethra among all the major body systems the immune system stands as a particularly intriguing one but you may be wondering why is it so intriguing it's because the immune system comprises of cells like macrophages neutrophils and asops which are tirelessly collaborating around the clock to defend you against the Relentless onslaught of pathogens aiming to disrupt your health so when we talk about pathogens we're referring to a diverse array of different kinds of threats whether it's viruses bacteria fungi protus or even parasitic worms just to name a few your body is equipped with external defenses against these various threats such as your skin which acts as the first line of defense it forms a protective barrier to prevent pathogens from entering your body similarly mucus membranes like the lining that we find in our nose are also able to keep pathogens out this first line of defense is a non-specific defense because it indiscriminately blocks any potential Invaders from entering your body however these defenses are not invaluable and pathogens can sometimes breach the system when this happens the immune system is ready with numerous strategies to handle the invasion drawing on its extensive experience in combating such threats so if pathogens managed to breach those initial barriers we have a second line of defense that comes into play which includes things like inflammatory responses to put it plainly imagine that you accidentally pricked your finger on a thorn that carries bacteria this penetration of bacteria causes the cells in our body like mass cells to respond to the injury and a potential bacterial threat these cells are filled with substances that assist with allergic and inflammatory responses one such substance is histamine when released histamine causes the nearby blood vessels to dilate which is just a fancy way of saying widen and when it dilates it's going to make it more permeable or leaky this dilation and increased permeability makes it easier for various types of white blood cells like certain macrofagos to reach and Infiltrate The affected area this allows these macrofagos to perform their Quint essential role engulfing and digesting pathogens Additionally the body deploys a compliment system which despite its name serves to enhance and support the immune systems functions this system can engage in both non-specific and specific immune responses in this case the release of complement factors helps draw more macrofagos to the site to eliminate the pathogens once this signaling ceases that affected area is going to begin to heal and return toward its normal State as the pathogen has been eradicated however when it comes to our second line of defense this response is still non-specific meaning that it reacts without knowing the exact nature of the threat like the unknown contents from that thorn this is what brings us to our third line of defense a more specific line of defense imagine that you're dealing with a cold virus spreading throughout your body this situation calls for a more targeted response for this particular kind of pathogen considering the need for a more specific and focused kind of immune response we're going to be stepping into the realm of an Adaptive immune defense when we talk about adaptive immunity we're talking about a more specific type of immune response that specifically targets antigens antigens are substances that the body recognizes as foreign often parts of pathogens adaptive immunity serves as the third line of defense where the two initial immunities known as non-specific defenses or innate immune responses are ultimately going to have failed to adequately control the pathogen like we'll see with the third line of defense we're going to explore two fundamental types of adaptive immunity we have cellmediated and humoral focusing first on cell mediated responses this is going to involve cytotoxic tea cells which is a specific type of white blood cell these cells can destroy other cells infected by a pathogen by inducing apotosis which is a process of programmed cell death or self-destruction this is achieved by releasing substances like perorin which creates holes in the infected cells membrane causing the cell to take in water and ions until it eventually bursts when infected cells are destroyed it's going to Halt the pathogen's ability to replicate within those cells the activation of cytotoxic tea cells requires specific stimulation for instance an infected cell may present a piece of the pathogen's antigen on its surface signaling that that cell has been compromised this flagging activates those cytotoxic tea cells prompting them to bind to the infective cell and initiate apotosis additionally cytotoxic tea cells can be stimulated in another way considering macrofagos that it have ingested those pathogens these cells can process and present that pathogen's antigen to their own surface that's when we're going to start to see helper tea cells what the helper te- cells are going to do is they're going to combine with that maccrage and with that combination they're going to start releasing chemical signals to activate those te- helper cells the ACT activated tea helper cells are then going to release those chemicals and stimulate those cytotoxic tea cells which are going to set them on a mission to find and destroy any infected cell further amplifying our immune response D helper cells play a crucial role not only in cell mediated responses but also in humoral responses acting as a significant supporter in both Pathways when it comes to the Adaptive immune response so what exactly unfolds during the humoral immune response want going back to our scenario where a maccrage is going to engulf a pathogen and present a piece of the pathogen's antigen on its surface this maccrage is then going to interact with a helper te- cell which in turn can activate a specific type of white blood cell known as a Bee Cell B cells have the capability to produce substances known as antibodies antibodies are predominantly found in the blood but they also can be found in mucus saliva breast milk among other fluids there are several classes of antibodies we begin with IGG which is the most abundant type of antibodies found in our system IGG is found in our body fluids and it protects against bacterial and viral infections by enhancing phagocytosis neutralizing toxins and triggering compliment system components IGA is found in our mucous membranes lining either our respiratory or our gastrointestinal tract as well as IA tears and breast milk IGA plays a critical role in mucosal immunity IGM is the first antibody produce and response to infection migm is primarily present in the blood and lymph fluid and it's very effective at forming complexes with antigens and activating the compliment system IG is mostly associated with allergic reactions and responses to parasitic infections IG is found in our lungs our skin as well as our mucous membranes and then lastly we have igd although it's less understood than the other antibodies igd is mainly found on the surface of immature B lymphocytes and in our respiratory tract where they play a critical role in initiating early immune responses when antibodies attached to an antigen they can neutralize this pathogen by hindering its movement reproduction as well as its ability to inflict damage this binding also acts as a signal to macrofagos to locate and devour that pathogen effectively marking it for Destruction activating B cells is a key component of the humoral response leading to the production of antibodies while B cells can be activated by a t- helper cell they can also be activated directly by free antigens that they encounter throughout the body it's important to highlight that memory cells play a significant role in both that humoral and that cell mediated response memory B and T cells are going to retain a memory of the antigens that they have encountered the difference is is that memory B cells are going to initiate those plasma B cells which then are going to create antibodies and just like the name suggests memory te- cells are going to activate our cytotoxic tea cells which are going to Target and destroy our infected cells lastly we have active immunity and passive immunity which are two critical forms of immunity that protect our body from pathogens but they function in distinctly different different ways active immunity occurs when an individual's immune systems produces antibodies in response to the presence of a pathogen so how is this type of immunity acquired well it's acquired through either direct exposure of the disease prompting a natural immune response or it can be through vaccinations or a dead or weakened pathogen is going to be introduced to stimulate an immune response without actually causing the disease active immunity is generally long lasting and can often provide life lifelong protection after the immune system has developed memory of that antigen common examples of this could be developing immunity after you catch a cold virus or even receiving a measles vaccine and then we have passive immunity which is provided when a person is given antibodies from another source rather than producing them through their own immune system this type of immunity can occur naturally such as when antibodies are transferred from a mother to her baby through the placenta during pregnancy or even breast smoke it can also be acquired artificially through antibody containing blood products such as immunoglobulin therapies or anti- serums which may be used to treat specific diseases passive immunity provides immediate protection but it's only temporary as antibodies are eventually broken down and do not result in the production of memory cells the protection might last a few weeks or even maybe a few months common examples of this could be newborns who are see receiving antibodies from their mother or a person receiving a rabies shot after an animal bite the skeletal system performs a crucial role of supporting the body and protecting our internal organs Beyond these functions it serves as a reservoir for essential minerals facilitates the production of red and white blood cells and enables movement in coordination with muscles it's important to remember that body systems do not operate independently many textbooks refer to muscular skeletal system emphasizing the interdependence between our skeletal and muscular systems an adult typically has 206 bones what's interesting is that babies are born with slightly more bones which often fuse together as they grow up into adulthood the human skeletal system is categorized into two main parts we have the axial skeletal and the appendicular skeletal starting with our axial skeletal which forms the Central axis of our body comprises of our skull bones the oses within our ears the hode bone found in our throat the vertebral column as well as our rib cage this structure not only supports our head and our neck movements but it helps facilitate breathing and it's also providing a foundational base when it comes to our appendicular skeleton the appendicular skeleton includes all the bones of our arms and the shoulder girdle which comprises of our c bones and our shoulder blades this is crucial when it comes to the function of our arms as well as our hands additionally encompasses the bones of our legs and our pelvic girdle which is vital for enabling movement next up we're going to dive into bone shapes and how we classify them starting with our long bones this term doesn't necessarily refer to their length in the most literal sense instead it's more related to that cylindrical shape and the fact that they are longer than they are wide these bones are typically involved in movement facilitated by muscle contractions examples of long bone can be our femur which is the prominent long bone fan on our leg as well as our tibia and our fibula in our arms we have the humoris the Anna and our radius and then lastly within our hands and our feet we have the fanges the metacarpal found in our hand and the metatarsals found in our feet unlike long bone short bones resemble cubes where their length and their WI with are going to be roughly equivalent these bones are mobilized through muscle contraction and provide significant stability examples can include the carpal that we find in our wrists and the tarsals that are found in our ankles next up we have sesamoid bones and these are small round bones that often resemble something like a sesame seed these types of Bones excel in handling pressure and are typically found embedded within tendons or muscles a well-known example of a sesamoid bone is our patella that's found in our knee flat bones despite their name are not actually flat they're often curved and thin these bones include the cranial bones that are found in our skull and our scapula or our shoulder blades which play a crucial role when it comes to body structure as well as protection and then lastly we have irregular bones and these kind of bones defy regular shape classifications you're going to see much more complex shapes that don't fit standard descriptions irregular B like the vertebrae are adapted to protect against a variety of forces and support bodily movements in multiple directions let's dive into the internal structures of Bones which consists of two primary bone tissues compact bone tissue forms the outer layer of our bones providing a hard durable surface for protection beneath our compact bone we have spongy bone tissue which comprises of our bone marrow and a network of porous honeycomb like structures on the atits you're going to hear words like cancellus or tricular bone which is just another way of referring to this spongy bone material you'll also find two types of bone marrow within our spongy bone we have red bone marrow and yellow bone marrow yellow bone marrow is rich in fat and serves as a reservoir for long-term energy storage red bone marrow is vital when it comes to hematopoesis which is the production of blood cells it can generate red blood cells which are crucial for transporting gases like oxygen and carbon dioxide white blood cells which play a key role when it comes to our immune defense and platelets which is not actually a true cell but a cellular fragment which is essential for blood clotting this complexity shows why bones are considered vascular because they possess a rich blood supply fractures that result from intense trauma such as long bones we see in our femur can not only lead to substantial internal bleeding but can also possess additional risks as we discussed since bones contain yellow marrow that stores fat severe fractures might release fat into our bloodstream while the body can generally manage a small amount of fat release a severe case might lead to a very rare but potentially serious condition known as a fat embolism syndrome another interesting side note is that in emergency situations when we're unable to get intravenous access in the arm or anywhere throughout the body Medical Treatments like fluid and medication administration can be administered directly into our bone marrow this route of administration is called intra osus meaning within the bone there are cells that play crucial roles in bone incar formation and maintenance starting with osteoblast these cells are bone Builders they are responsible for creating new bone and as they mature they differentiate into osteocytes Osteo cytes are the primary cells in the bone tissue and are essential for maintaining our bone structure and lastly we have OC class which are bone resorbing cells what's fascinating about OC class is their method for breaking down bone they contain numerous lomes which are organel filled with enzymes these enzymes along with acids produced by the Osteo class effectively dissolve bone tissue this process is vital when it comes to bone remodeling and calcium homeostasis in the body you might ask yourself why does the body intentionally break down bone the reason is that the body continuously adapts to various stresses they do this through a process known as bone remodeling where old bone is systematically removed and new bone is formed in its place this continuous cycle involves several distinct phases there's resting resorption reversal formation mineralization and then back to our resting state during our initial resting state the bone surface and bone cells are ocytes osteoblast and OC class are all inactive as we move into the resorption stage you're going to find that OC class are going to attach to the Bone surface and create an acidic environment that's going to help dissolve that mineral component of the bone matrix it's also going to degrade that organic Matrix resulting in the formation of a absorption pit this phase is crucial for removing that old damaged and unnecessary bone tissue forming new bone and helping regulate our calcium levels after absorption we have a brief period of reversal where we're going to see mononuclear cells appear on the bone surface these cells are going to Signal the end of that resorption phase and the start of the formation phase in that formation phase you're going to find that osteoblasts are going to begin to lay down n osteoid at the resorption site osteoids are just unmineralized bone matrix osteoblasts are going to replenish the bone that was lost during the resorption phase maintaining that skeletal strength and integrity in mineralization the newly formed osteoid begins to mineralize calcium and phosphate from the body fluids crystallize onto the collagen fibers of the osteoid it's going to harden that new bone to restore the bonees mechanical iCal strength and its ability to support and protect the body Additionally the process of bone breakdown serves an important physiological Purpose By releasing minerals that the body needs a key mineral that is stored in bones is calcium specific hormones from the endocrine system regulate the release of calcium from the bones and its disposition back into them calcium plays crucial roles for various bodily functions for instance as we demonstrated in the video on the muscular system system calcium is essential for the activation of muscle contraction bone cells collaborate closely with other cell types such as condr blasts condr blasts are responsible for producing the connective tissue known as cartilage as they mature condr blasts become condr sites which are essential for maintaining the structure of the cartilage cartilage plays a critical role in supporting bone structure particularly in joints where bones meet it also acts as a template for bone development during fetal development cartilage formed by those condr blasts initially serve as the framework for future bone growth over time most of the cartilage Matrix is replaced by bone though not entirely lastly we're going to discuss what happens when a bone fractures initially a fractured hematoma is going to form at the side of the break this hematoma is a collection of blood resulting in that high vascularity from the bones the accumulation of blood can block the supply of near by bone cells typically causing them to die fortunately condr sites and osteoblasts quickly spring into action to stabilize the fracture they do this by forming a callus which is a thicken part of the soft tissue similar to what you would see if we had that thickening of our skin from lifting weights with our hands the internal callus is primarily made up of cartilage and the external callus is going to be a mix of both cartilage as well as bone these calluses function together to secure and stabilize that fracture site during the healing process osteoblast plays a crucial role in removing the damaged portions of the bone clearing way for its repair subsequently osteoblasts begin the remodeling phase creating new bone to replace what was loss there are five different kinds of fractures that you're going to need to be familiar with a closed fracture also known as a simple fracture is a fracture that does not penetrate the skin the broken bone is contained within the body minimizing ing the risk of infection as well as external bleeding open fractures however also known as compound fractures occur when the bone breaks through our skin this type exposes that bone as well as deep tissues to the external environment greatly increasing our risk of infection communed fractures are fractures where the bone shatters into three or more pieces this type of fracture is particularly severe and often occurs due to high impact trauma impact Ed fractures also known as buckle fractures often occur when the ends of the bones are driven into each other typically seen in arm fractures among children and then lastly we have green stick fractures which again are common among children because their bones tend to be softer and more flexible when we're taking a closer look at a green stick fracture this occurs when the bone kind of bends or it cracks but it does not break all the way through to begin we're going to start by recognizing common anatomical terms that you're going to need to know for your tests starting with the terms for our head we have which stands for our head cranial which is our skull facial for our face frontal for our forehead temporal for our Temple orbital or ocular for our eye optic for our ear bual for our cheek nasal for our nose oral for our mouth and mental for our chin moving down from our neck to our abdomen we have cervical for our neck axillary for our armpits brachial for our arm anti brachial which is our forearm carpal for our wrist Palmer for our Palm polex for our thumb or digital or fangi they're used interchangeably for our fingers we have sternal for the breast bone thoracic for our chest mamory for our breast abdominal for our abdomen and iCal for our Naval and then lastly for our anterior view we're going to move from our hips all the way down so we have coxa for our hip femoral for our thigh patella which is the front of our knee cural which is our Shin pedial for our foot tarsel for our ankle digital of fangi actually stands for our to dorsum really means the top of or the back of so you can have the dorsum of your foot or you can have the dorsum of your hands halex which stands for our great toe and just like I said dorsum which stands for the back of our hand so they're going to be used interchangeably make sure you recognize that the dorsum can be the back of your hand and it can be the top of your foot we have manual which stands for our hand pelvic for our pelvis inguinal for our grin and pubic for our pubis now that we covered everything on the interior side we want to cover everything on the posterior side which is just a fancy way of saying our back so starting at the top we have the occipital which is the base of our skull acromial which is our shoulder scapula which is our shoulder blade vertebral which is the spinal column dorsal which is our back o cranial or cubital which is the back of our elbow we have lumbar for our loin we have sacal between our hips cagal which is our tailbone Glu which is our buttock paranal which is that area between our anus and our external genitalia we have poo which is the back side of our knee surl which is our calf plantar which is the sole of our foot and Cal which is our heel next up we're going to look at the different kind of planes you're going to need to know for the test so what I want you to imagine as you take a look at these pictures is either you are stuck inside the wall or you're leaning up against the wall right so when we're leaning against the wall we're stuck inside the wall we're only going to be able to move in certain directions we're not going to be able to come out of the wall right we're just going to be able to move alongside it make sure you understand this concept cuz it's going to be really important for you to understand when it comes to movement with these planes starting with our transverse plane the transverse plane is a horizontal plane what it's going to do is it's going to divide our body into our upper which is our Superior parts and our lower which is our inferior parts so when we talk about movements in the transverse plane we're talking about rotational or twisting movements only on the body's vertical axis so as you can see here in this picture it looks like your arms and half of your body is kind of stuck in this wall right so the only thing that we're going to be able to do is Twist and Turn turn I'm not going to be able to move my arms right cuz they're stuck in the wall and I'm not going to be able to move at my waist to Bend forward or backwards so the only thing that I'm going to be able to do is to twist and turn next up we have the frontal plane it's also known as the corneal plane so they are used interchangeably when it comes to atits what this plane does is it actually separates our body from our posterior which is our back and our anterior which is the front so movements when it comes to the frontal plane are going to involve Motions like side side to side away from and towards the midline so we have abduction which means we're moving away from the midline and we have adduction which means we're moving back towards the midline you also have the ability to raise your arms or your legs out to your side exemplifying the movements within this frontal plane and then last up we have our sagittal or lateral plane again they're used interchangeably on the te's and this particular plane divides Us in half but at this time we're looking at our left side and our right side movements within the sagittal plane are those that occur with forward and backward right so flexion would be bending and extension would be straightening that's the typical movements that you're going to see in the sagittal plane and lastly the teas loves to test you on anatomical positions of different body parts so we're going to be using terms like interior posterior medial lateral so let's break each one of these down so starting with anterior this this is the front or forward-facing side of the body so if you are facing an individual and that individual is also facing you as well it's everything that you're going to see on the front so a good way to remember this is just everything that's in the front everything else is more posterior so if you think about it a common example of this could be the nose is anterior to the ear and then next up we have posterior which is the complete opposite of our anterior this is the back or rear side of the body so if somebody had their back turned to you and you were looking at their back side you're technically looking at their posterior side so we could say that the spine is posterior to the chest and next up we have medial and what medial means is that structures that are closer to the midline of our body so that's like our sternum bone right everything that's really close to our midline so we could say that the nose is more medial than our eyes and you guess that the opposite of medial is lateral so lateral structures mean that they're further away from the midline of the body so we're talking about lateral we could say that the ears are lateral to the eyes and just like we talked about before with our transverse plane we have Superior and inferior Superior means that the position is going to be happening above or higher than another body part so our eyes are superior to our mouth and when it comes to inferior we're talking about the position being below or lower than another body part so we could say that the mouth is inferior to the eyes and lastly we have proximal versus distal so proximal refers to the point of attachment to the limb to the body proximal means closer so anything that attaches to the central portion of our body whether it's our femur our humorus that's in our arms right they're going to be more proximal because they're directly attaching to the body so in this case we could say the shoulder is proximal to our elbow and when we talk about disle we're talking about about things being further away from the body right it's not directly at the attachment point it's much further on down the line so we could say that the fingers are distal to our wrist and that's everything that you're going to need to know I love human anatomy and physiology of course if you have any questions make sure that you leave them down below I love answering your questions head over to nurun store.com there's a ton of additional resources in order to help you Ace those ait's exams and as always I'm going to catch you in the next video bye he