Transcript for:
Overview of Major Human Body Systems

hey guys welcome to this mometrix video about the respiratory system every one of the systems in the body plays a critical role in our ability to function but the respiratory system is particularly important the respiratory system allows us to breathe without it we can't take in the oxygen that helps us survive and we can't expel the carbon dioxide that can result in dangerous health issues [Music] the respiratory system includes the nose mouth pharynx or throat larynx or voice box trachea or windpipe bronchi or large airways in lungs each plays a vital role in the respiratory system's five main functions let's take a look at those five functions it's a process called pulmonary ventilation air comes in through our noses and mouth and then passes through the pharynx larynx and trachea before entering the lungs when we exhale the air goes back out of our bodies by the way the trachea or windpipe connects the pharynx and larynx to our lungs secondly when the respiratory system exchanges gases that's called external respiration when air goes into the body it supplies the lungs with oxygen as that oxygen comes in the lungs expel carbon dioxide a little later we'll talk more about why it's so important that the body regulates carbon dioxide that leads us to our third function called internal respiration internal respiration exchanges gases between the bloodstream and tissues the bloodstream carries oxygen to cells and expels carbon dioxide the respiratory system also helps us with sound and that's the fourth function on our list when we exhale our air goes from our lungs to the larynx more commonly known as the voice box when air moves through the vocal cords they vibrate and that creates sound the respiratory system helps us smell and that's the fifth and last function ever wonder why you can't smell anything when you have a clogged nose it's because little fibers in your nose the olfactory fibers have been blocked by mucus or some other substance so those are the respiratory systems five main functions but let's talk a little more about carbon dioxide the respiratory system does a delicate push and pull by pulling in oxygen and pushing out carbon dioxide sometimes the body's internal regulation doesn't work correctly resulting in a condition called hypercapnia hypercapnia can cause a host of health issues including fatigue headaches and dizziness in the most severe cases hypercapnia can cause seizures palpitations and panic attacks let's take a more detailed look at the upper and lower respiratory tracts the upper respiratory tract contains five main structures the nose nasal cavity mouth pharynx and larynx the nose knows it really does the nose and its nasal cavity govern our sense of smell with it humans can differentiate between 5000 and 10 000 different sense the nose has an internal and external structure the external structure contains the root which is located between the eyebrows the bridge which connects the root to the rest of the nose and the dorsal nasai which extends from the root to the tip of the nose the external nose also contains the frontal nasal and maxillary bones and the septal and major alert cartilages we know the internal nose as the nasal cavity it's lined with hairs and a mucous membrane that acts as a human air filter the cavity warms moisturizes and filters air that enters the body before it reaches the lungs but that's not all the nose also has an intricate sinus system sinuses produce mucus to moisturize the inside nose and protect us from dirt dust and other organisms there are three different sinuses there are two maxillary sinuses located on both sides of the nose just below the cheeks they are collectively the largest sinus and the one that can cause some pain the maxillary sinus drains into the nose through a small hole called the osteum when the ostea become clogged that can result in sinusitis or sinus infection the ethmoid sinus is located between the nose and eyes and the frontal sinus is located above each eye for most of you the mouth is the easiest structure to remember because we use it all the time we ingest food through our mouth which can also be called the oral cavity small glands in three pairs of salivary glands keep the mouth moist we need that moisture to soften and swallow food there are also two membranes in the mouth the gums and the tongue the gums support our teeth and the tongue contains our taste buds now let's move on to the pharynx the pharynx has three separate sections the nasopharynx the orozopharynx and the hypopharynx the nasopharynx located above the soft palate is the mechanism that lets you breathe through your nose the oropharynx connects the nose in the back of the mouth to the esophagus the hypopharynx is the passageway for food food goes from the mouth through the hypopharynx and esophagus and then into the stomach let's talk about the larynx the last part of the upper respiratory tract we'll discuss we know the larynx is the voice box because without it we wouldn't be able to talk but the larynx does much more the larynx allows our air to pass through the respiratory tract but it also protects the trachea by ensuring food and drink don't block the airway the larynx itself has three sections the supraglottis glottis and subglottis a network of nine cartilages connect by muscles and ligaments form the larynx that's the upper respiratory tract let's take a look at the lower respiratory tract the lower respiratory tract also has four main components the trachea lungs bronchi and diaphragm let's start with the trachea the trachea is the main airway to the lungs and is more commonly referred to as the windpipe the trachea connects the larynx to the left and right bronchi in the lungs we need our lungs to pull in air and breathe we talked earlier about the body's need to pull in oxygen and push out carbon dioxide and that's what our lungs do for us our lungs are an indispensable part of our breathing system they're protected by the sternum ribcage and vertebrae the process of profusion helps fluid pass to an organ or tissue the alveoli produce a fluid called surfactant which helps prevent the lungs from collapsing tidal volume represents the normal volume of air that moves in and out of a body when we inhale and exhale the lungs have an intricate system of members and functions that help it stay healthy and in proper working order the pleura a membrane on the inside and the outside of the lungs secretes a fluid that lets the lungs move against the ribcage when we breathe the right lung has three lobes and the left lung has two that's because the left lung must make room for the heart the lobes all have the same function as they all bring oxygen into and remove carbon dioxide from the bloodstream let's move on to the bronchi there's a tube in each lung called a bronchus that connects to the trachea there are two main bronchi that are extensions of the trachea that help push air to and from the lungs the diaphragm is the primary muscle used in breathing contracting in and out as you breathe the diaphragm is located below the heart and the lungs it has three main openings and they each provide a critical function that's because these openings let other structures pass between the chest and the abdomen the esophageal opening provides a passageway for the esophagus and the vagus nerve the aortic opening allows the aorta and the thoracic duct to pass through the aorta transports blood from the heart and is the body's main artery while the thoracic duct is the lymphatic system's main vessel now that we understand the upper and lower respiratory tract let's take a look at the respiratory system zones the respiratory system has a conducting and a respiratory zone the conducting zone provides a continuous passageway for incoming and outgoing air to travel the conducting zone consists of the nose the pharynx the larynx the trachea the bronchi and the bronchioles it's important to remember that all structures in the conducting zone only deal with air we talked about the gas exchange systems earlier and that's where the respiratory zone comes in the respiratory zone is only involved in oxygen and carbon dioxide exchange and consists of the bronchioles the alveolar ducts and the alveoli the alveoli are very small air sacs in the site of the exchange of oxygen and carbon dioxide the bronchi are the main passageways attached to the lungs and the bronchiole connects the bronchi to the alveoli now that we understand the respiratory zone let's talk more about ventilation ventilation is the process by which air moves in and out of the body we breathe in that's inhaling we breathe out that's exhaling inhaling and exhaling each have opposite movements inhale and the diaphragm moves downward exhale and the diaphragm moves up when you inhale the ribs push out and air fills the lungs exhale in the ribs relax as air comes out of the lungs hyperventilation and hypoventilation can occur while breathing and both can make you sick hyperventilation happens when you breathe faster than normal when you breathe fast you take in too much oxygen in the blood and that can make you feel faint or dizzy during hypoventilation you're breathing too slowly and that results in too much carbon dioxide entering the bloodstream that can result in fatigue headaches and other illnesses so that's our overview of the respiratory system the part of our body that helps us breathe while expelling carbon dioxide from our system welcome to this video on the cardiovascular system the cardiovascular system also known as the circulatory system is made up of the heart blood vessels and blood that circulates throughout the body you will also hear the term the cardiopulmonary system which is referring to the cardiovascular system along with the trachea bronchi and lungs the pulmonary portion in this video we will take a closer look at the cardiovascular system the heart's basic anatomy two types of circulation how blood circulates through the heart what causes the heart to beat and the makeup of blood the heart is a muscle that sits in the upper left side of the chest behind the ribcage it weighs roughly 10 ounces and is about the size of a clenched fist the heart is made up of a system of chambers and valves the chambers momentarily hold blood while the valves allow blood to flow in one direction to the next chamber it beats about a hundred thousand times a day and sends blood throughout some sixty thousand miles of blood vessels there are several components that help the heart function properly the heart is composed of three layers the epicardium the myocardium and the endocardium the epicardium forms the outermost layer of the heart wall and protects the heart's inner layers it contains the coronary blood vessels which supply blood to the heart the myocardium layer is like a pump contracting to pump blood out of the heart and then relaxing to let the heart fill with blood again the endocardium the third layer of the heart is a thin inner layer that lines the heart's chambers let's take a look now at the internal anatomy of the heart the heart is divided up into four chambers the right atrium and right ventricle and the left atrium and left ventricle when we refer to the right side of the heart we're referring to the side of the heart in relation to the right side of a person's body the left side of the heart is on the left side of the body the heart also has four one-way valves the right atrioventricular valve also called the right av valve or tricuspid valve the pulmonary valve or the pulmonary semilunar valve the aortic valve and the left atrioventricular valve also called the left av valve or the mitral bicuspid valve one way or unidirectional flow is important if the valves are leaking and allow blood to flow in both directions then the heart has to work harder to pump the same amount of blood this is called valve regurgitation now that we've looked at the chambers and valves of the heart let's talk about the blood vessels that connect everything and allow for the proper functioning of the heart as a rule veins bring blood towards the heart and arteries which starts with an a carry blood away from the heart the major veins that bring blood to the heart are the superior vena cava and the inferior vena cava the superior vena cava brings blood to the heart from the upper body while the inferior vena cava brings blood from the lower body other veins in the heart include the right pulmonary veins and the left pulmonary veins the right and left pulmonary veins bring oxygenated blood from the lungs into the heart other major veins include the jugular vein left and right subclavian veins hepatic portal renal veins and the common iliac veins moving further from the heart and closer to the extremities the blood vessels get smaller and the veins become venules the heart also has arteries taking blood away from the heart some major arteries include the right pulmonary artery the left pulmonary artery and the aorta the aorta branches off into smaller arteries and is responsible for distributing blood throughout the body once it's been oxygenated so this is the biggest strongest artery in the body the left and right pulmonary arteries carry deoxygenated blood to the lungs where the blood gets oxygenated the heart also has coronary arteries that wrap around the outside of the heart and supply blood to the heart muscle they are called the left coronary artery and the right coronary artery other major arteries in the body include the carotid artery the subclavian artery common iliac artery femoral artery and renal artery as we move further from the heart these arteries become arterioles and arterioles become very fine capillaries arteries and veins are connected by way of microscopic blood vessels called capillaries that make up a capillary bed capillary beds are a network of capillaries located between arterioles and venules where nutrients and wastes are exchanged now let's look at the circulation of the blood through the body there are two types of circulation pulmonary circulation where blood moves between the heart and the lungs and systemic circulation which is the path blood takes between the heart and all organs and tissues in the rest of the body pulmonary circulation transports deoxygenated blood to the lungs to absorb oxygen and release carbon dioxide the oxygenated blood then flows back to the heart where it gets pumped out to the systemic circulation the rest of the body let's take a closer look at the pathway of blood as it travels through the heart starting with oxygen poor blood in the superior vena cava this blood will flow into the right atrium where it is then forced through the right av valve into the right ventricle blood passes through the pulmonary semilunar valve and is forced up into the pulmonary arteries so that it can be oxygenated in the lungs once the blood is oxygenated it re-enters the heart through the right and left pulmonary veins and travels into the left atrium from here the blood is forced through the left av valve and into the left ventricle finally the blood travels through the aortic valve and into the aorta where it can be distributed to organs and tissues throughout the body that need oxygen most the real gas exchange takes place in the capillaries where tissues trade their carbon dioxide for oxygen the blood is carrying now that the blood has given its oxygen to the tissues it returns by way of veins into the superior and inferior vena cava where we start it so that it can flow back through the heart and repeat the process as the heart beats it goes through what's called a cardiac cycle in which there are two phases called the diastole and systole systole occurs when the ventricles contract and pump blood out of the heart and diastole occurs when the ventricles relax after contraction and refill with blood this systolic and diastolic process measures blood pressure systole or the top number is basically the pressure required to pump blood out of the heart and diastole the bottom number is the pressure that remains when the heart is in a resting state between heartbeats you may be wondering what causes the heart to beat electrical impulses from the heart muscle the myocardium cause the heart to beat or contract known as the cardiac conduction system a group of specialized cardiac muscle cells in the walls of the heart send signals to the myocardium causing it to contract the main components of the cardiac conduction system are the sa node av node bundle of his bundle branches and purkinje fibers the cyanoatrial or sa node located at the top of the right atrium starts the sequence by causing the atria to contract the sa node is referred to as the natural pacemaker from there the signal travels to the atrioventricular or av node through the bundle of hiss down bundle branches and through the purkinje fibers causing the ventricles to contract these signals of electrical current can be seen on a graph called an electrocardiogram ekg now we'll take a quick look at the fluid that flows through our cardiovascular system blood has four main components plasma red blood cells white blood cells and platelets the blood that runs through the veins arteries and capillaries is known as whole blood whole blood contains about 55 plasma and 45 blood cells the average man has about 12 pints of blood and the average size woman has about nine pints the liquid component of blood is called plasma which transports blood cells nutrients waste products antibodies clotting proteins and hormones throughout the body red blood cells contain the protein hemoglobin that carries oxygen from the lungs to the rest of the body and then returns carbon dioxide from the body to the lungs to be exhaled red blood cells are made inside our bones and get their red color from the hemoglobin white blood cells are the fighters because they protect our bodies against infection platelets are actually small fragments of cells that form small clots to help the body stop bleeding blood has several different functions including transporting oxygen and nutrients to the organs and tissues in our body carrying cells and antibodies that fight infection taking waste products to the kidneys and liver so they can filter and clean the blood and forming blood clots to stop excess bleeding now that you're familiar with the heart's anatomy and the path blood takes as it circulates through the heart and body let's take a look at this quick review question based on what you've learned about the circulation of blood through the heart and lungs which of the following vessel or vessels would contain oxygenated blood is it a inferior vena cava b right and left pulmonary arteries c right and left pulmonary veins d the aorta or e both c and d the correct answer is e the pulmonary veins and the aorta the inferior vena cava brings deoxygenated blood from the lower body to the heart and the pulmonary arteries are also carrying deoxygenated blood to the lungs to get oxygenated blood in the right and left pulmonary veins just came from being oxygenated in the lungs and the aorta is carrying that oxygenated blood from the left ventricle to the rest of the body hey guys welcome to this mometrix video about the gastrointestinal system the gastrointestinal system is also called the digestive system for an obvious reason it's where all the facets of digestion take place that means everything from the way food comes into our body how our system breaks down that food and how waste exits our body it's a complicated but important process so let's take a look at our gastrointestinal system in more detail our gastrointestinal system does more than just digest our food our bodies need nutrients from food and water for us to stay healthy and survive our gastrointestinal system breaks down food into very small pieces that can be absorbed by the body and used as a sort of fuel that we need to function major nutrients include proteins which help fight infections and make healthy cells carbohydrates provide a source of energy minerals perform several functions like keeping bones strong with calcium or providing an adequate supply of iron that helps transport oxygen in our blood so yes digestion is important but our gastrointestinal system does so much more so what happens once we ingest our food let's find out we all have a gastrointestinal tract called the gi tract this long passageway starts at the mouth and ends at the anus think of the gi tract as the entrance and exit point of our food the gi tract is also called the digestive tract or the alimentary canal it passes a number of solid and hollow organs and we're going to take a closer look at those now the gi tract has three solid organs the liver the gallbladder and the pancreas the mouth esophagus stomach small intestine large intestines and anus are the hollow organs those hollow organs push food through our body via a process called peristalsis it's the push and pull that allows food to move from one muscle to another the muscle behind the food contracts and the muscle in front of the food relaxes allowing for easy passage that's the short of how food moves through our body now we'll take a journey through the gastrointestinal system and a more detailed look at its parts we'll start at the mouth the place that chews and ingests our food after chewing we swallow and the tongue plays its important role by pushing the food into our throat the epiglottis a small flap covers the windpipe so food doesn't get stuck there and now that we've swallowed the food the digestive journey starts after we swallow the food passes through the esophagus and at that point peristalsis begins when the food reaches the end of the esophagus it passes through the lower esophageal sphincter and then into the stomach have you ever gotten heartburn or acid reflex you see the sphincter is supposed to stay closed so food doesn't go back up into the esophagus when the sphincter relaxes at the wrong time and food backs up well you get that heartburn feeling but if everything goes as it should the food has now made its way into our stomach and that's where it goes for a nice digestive swim digestive juices coat the food in liquid and break them down so they can continue their journey through the body but before we continue along our journey we need to talk a little more about the stomach a single organ that has five different parts those parts are the cardia the part of the stomach closest to the esophagus the fundus which is located next to the cardiac and is the upper part of the stomach the main part of the stomach called the body the antrum the lower portion of the stomach where food and liquid mix with digestive juices and the pylorus which lets food pass from the stomach into the small intestine remember the pylorus because that plays an important role in our next stop the small intestine once in the small intestine nutrients head into the bloodstream and waste starts the process of moving out the small intestine has three sections that we'll briefly talk about here the first section the duodenum is the smallest section when food passes from the stomach it enters the duodenum through the pylorus the middle section of the small intestine the jejunum absorbs sugar and amino and fatty acids before it moves on to the final part of the small intestine the last part called the ilium absorbs nutrients that were not digested by the jejunum those nutrients include carbohydrates minerals and fats as food leaves the small intestine it enters the large intestine so the small intestine is about 23 feet long why is the large intestine labeled large if it's only about six feet long you see the large intestine at three inches has a larger diameter than the small intestine which is just about an inch the term large intestine refers to the larger diameter not the total length large intestines takes food breaks it down even further and turns it into waste there are several sections of the large intestine that participate in this process and we'll go over those here large intestines has four parts called the ascending colon the transverse colon the descending colon and the sigmoid colon the ascending colon is the beginning of the large intestines and has two important parts the cecum and the colic or the ileocecal valve the valve is at the end of the ascending colon and separates the cecum from the small intestine the valve prevents food and other materials from flowing back into the small intestine this process of fermentation takes place in the transverse colon as food leaves the ascending colon and enters the transverse colon fermentation further breaks down the food by removing water and nutrients once the fermentation process finishes the remaining waste forms before we talk about the next step here's another note about the transverse colon two arteries the medial colic artery and the inferior mesenteric artery provide a constant supply of oxygenated blood to the transverse colon why because the blood flow keeps the intestine healthy and prevents illnesses like intestinal ischemia let's continue our journey food is moved from the small to the large intestine and has made its way to the transverse colon the next stop the descending colon the descending colon stores food before it's emptied into the rectum it's also the point at which feces start to become solid from there waste enters the sigmoid colon and that's where waste solidifies the muscular walls of the sigmoid colon contract to push feces into the next part of the gastrointestinal system the rectum the rectum acts as a holding tank for waste the rectum holds feces until it's ready to be expelled in other words that's where waste stays until you're ready to use the bathroom from there the waste exits through the final stop in the gastrointestinal system the anus so that's the journey food takes now let's take a closer look at the enzyme production in the gastrointestinal system carbs proteins nucleic acids and lipids are all major elements in biological molecules life can't exist if the body is missing any one of these molecules so it's no surprise that they each play a role in the gastrointestinal system here's how there are three enzymes that help break down carbohydrates the salivary amylase enzyme in the salivary gland that helps break down starches and sugars this process takes place in your mouth the pancreatic amylase in the pancreas completes carb digestion and produces glucose lastly the maltase enzyme in the small intestine breaks down disaccharides into single sugars there are also three enzymes that help break down protein pepsin which is produced in the gastric gland and trypsin produced in the pancreas both help digest protein in food peptidases produced in the small intestine also breaks down proteins but in this case for the purpose of recycling amino acids nuclease and nucleosidase are two enzymes associated with nucleic acids dna and rna are the two main nucleic acids both enzymes are produced in the pancreas lipids those fatty and oily substances in the bloodstream are broken down by lipase in bile salt lipase is found in the pancreas while the liver makes bile salts in the gallbladder stores it technically bile isn't an enzyme it's a salt that mixes or emulsifies lipid into fatty acids we mentioned cells in patches and they also play an important role chief cells located in the stomach convert pepsinogen to pepsin which we already know helps digest protein goblet cells found in the respiratory and intestinal tract secrete mucus parietal cells are crucial to the production of hydrochloric acid which helps with digestion finally peyer's patches the lymphatic tissues found in the ilium of the small intestine protect the gastrointestinal tracts from pathogens so that's our overview of the gastrointestinal system the system that acts as an entrance for food and an exit for waste as we noted the gastrointestinal system also plays a role in breaking down nutrients that become fuel for our body hey guys welcome to this mometrix video about the muscular system muscles aren't just those things you make when you flex your arms muscles go much deeper than that muscles control movement they help us with our posture they control a number of voluntary and involuntary movements in our body the human body contains roughly 700 muscles that make up half of our body weight that's a lot of muscle so let's take a look at the muscular system and the critical roles it plays in our body we have muscles from head to toe we have muscles in our head and neck chest and upper back abdomen and lower back arms and hands and legs and feet they all have muscle and elastic tissue that controls our movement the muscular system consists of skeletal smooth and cardiac muscles let's start with the skeletal muscles we bend we left we twist and we turn we can think the skeletal muscles for that these muscles which are the majority of muscle tissue in our body power our skeletal movement when you think of movement you might think of walking or stopping but skeletal muscles do so much more than that these muscles help with our posture by holding us upright muscles also keep our skeleton stable these muscles hold joints in place so they don't become dislocated they also play a crucial role in a number of voluntary movements like swallowing that are important to other parts of our body these voluntary movements result in a push and pull or relax and contract state lifting your legs or bending your arm are examples of voluntary movements since skeletal muscles have their own integrated tissues they're actually organs the tissues made of microfibers look as if they have a series of ridges which makes the muscles striated biceps and triceps are examples of striated muscles there are two types of skeletal muscles slow twitch and fast twitch slow twitch muscles don't easily tire so they're best for endurance activities if you're going on a long walk or bike ride those slow twitch muscles kick in when you think of a burst of energy think of a fast twitch muscle since these muscles quickly contract they're best used for rapid movements like if you're trying to sprint but the fast twitch muscles do easily tire while other types of muscles get to rest the heart muscle doesn't it beats every moment of every day for your entire life pushing blood out of your heart and then relaxing to fill it unlike the skeletal muscle the cardiac muscle is controlled by involuntary movements the smooth muscle doesn't have the same striation that the skeletal muscle or cardiac muscles have that's why these muscles are called smooth you'll find these muscles in the walls of hollow organs acting involuntarily in a number of the body's activities smooth muscles for example contract to push food through the intestines and urine through the bladder smooth muscle in the uterus help in the birthing process during contractions you'll find smooth muscles around the respiratory digestive and reproductive tracts the stomach and lungs are two more examples of smooth muscles muscle contains two major proteins called myosin and actin myosin is a thick filament that contains chemical energy that controls a specific movement and plays an important role in muscle contraction myosin controls all of the movements you make if you're reaching for the remote control beating an egg in a dish or turning the pages of a book that's myosin at work myosin works as the power plant for voluntary or involuntary movements by transferring energy myosin works with actin a protein in the thin filament that also plays a role in motion so how do they work together when the muscles contract the thick myosin filaments grabs onto the thin actin filaments sarcomere is the name of the myofibril unit that contains myosin in actin we've mentioned that muscle performs a number of important functions let's take a closer look at what they are when you move your head side to side or up and down those are the head and neck muscles at work not only that the muscles in our jaw control chewing muscles in our neck even help us swallow muscles in our face help us smile face muscles are also unique because most of them connect bones to skin in other parts of our body muscles generally connect to and move bone there are a number of important chest muscles but none is more important than the pectoralis major it helps the shoulder joint move in different directions giving us the ability to raise our arm or shoot a basketball the pectoralis major serves an even more important function because these muscles keep our arms attached to our body here's an easy way to think about the muscles in the chest and upper back these muscles pretty much control our ability to rotate whether it's our head neck or trunk we also wouldn't be able to hold our head up without the support of these muscles the muscles of the abdomen protect vital organs like the liver kidneys and gallbladder but these muscles also help the body bend at the waist this area contains three major muscles anyone who has six pack abs is looking at their rectus abdominis which is located at the front of the body the rectus abdominis is that layer of muscle underneath fat when the fat burns away you'll see the ridges along your abdomen or as they're commonly called abs the external obliques located on each side of your body help our body rotate lastly the latissimus dorsi muscle located in the middle of the back plays a critical role in extending and rotating the arm we all know the importance of our arms and hands the muscles here help us do everything from typing to writing to painting the muscles help with the strength and ability to lift a frying pan engage in physical activity and squeeze three muscles the brachialis biceps brachii and the brachioradialis work together so that we can flex and extend our upper arms the wrist hands and fingers by and large don't move muscles on their own forearm muscles like the flexor carpi radialis and flexor digitorum superficialis control the flexing movement these flexor muscles control the ability for the joint to bend other muscles called extensors control the ability to open the joint if you want to run or jump or just maintain your balance you need the muscle in your legs and feet think of all the movements centered in this region of the body the muscles stretch contract relax stabilize and rotate joints these leg muscles are called long muscles because they stretch the quadriceps located in the front of the thigh are the leanest and strongest muscles in the body the hamstrings are on the back of the thigh and anyone who has ever pulled a hammy knows exactly how painful that is calf muscles connect to the heel making it a pivotal part of moving the foot ankle and knee so that's our overview of the muscular system the system that gives us flexibility and provides the structure for movement and strength hey guys welcome to this mometrix video about the endocrine system the endocrine system plays an important role in our bodies it regulates several critical functions including growth reproduction and stress in this video we'll delve into these different functions and see how useful it is in our everyday lives the endocrine system consists of a series of glands that produce and secrete hormones those hormones regulate several human body functions including growth sexual function and reproduction the endocrine system contains the pituitary gland the thyroid gland the parathyroid glands adrenal glands and the ovaries and females in the testicles in males these glands are in or near a number of organs including the brain kidneys and the pancreas let's take a more detailed look the pituitary gland is a small organ with a big responsibility the gland is only the size of a pee but it's referred to as the master gland because it secretes hormones throughout your body these hormones direct body processes or force other glands to produce hormones the pituitary gland has two parts the anterior located at the front of the gland and the posterior located on the rear the anterior and posterior sections each produce specific hormones let's take a closer look at the two we'll start with the anterior pituitary which produces far more hormones than the posterior we're going to take a look at nine of these hormones first the growth hormone or gh this hormone stimulates growth focusing on the bones and muscles gh stimulates growth in children and then in adults helps maintain muscle and bone mass number two is prolactin nearly eight in ten mothers breastfeed their newborn babies according to the centers for disease control prolactin plays a critical role because that's the hormone that stimulates breast milk production prolactin always affects sex hormone levels and fertility in women and men next we have the adrenocorticotropic hormone this hormone stimulates cortisol the so-called stress hormone it's also known for controlling the human fight or flight instinct and works with the brain to manage emotions like mood and fear cortisol also plays several other important roles it increases glucose which increases blood sugar it also regulates blood pressure boosts energy and manages the carbohydrate fat and protein use in the body when the body is under stress it produces more cortisol number four is endorphins when you feel pain or pleasure you have endorphins to think endorphins are often referred to as the body's natural painkiller but the hormone is also the body's pleasure center the body releases endorphins during periods of stress including exercise and works with the brain to lessen our perception of pain next we have encephalins these are closely related to endorphins because they also release hormones that help control pain number six is the beta melanocyte stimulating hormone this helps protect the skin from ultraviolet radiation it also can help suppress appetite for number seven we have the luteinizing hormone which helps stimulate testosterone production in men and estrogen production in women next we have the follicle stimulating hormone this hormone has a different function in men and in women in women the hormone helps produce estrogen and egg growth while in men this hormone is critical in sperm production finally number nine is the thyroid stimulating hormone this is your regulatory machine because it regulates the number of hormones the thyroid releases it's critical to metabolism those are the components of the anterior pituitary now we'll look at the two components of the posterior pituitary first we'll look at the vasopressin it's the hormone that helps the body prevent dehydration by helping you conserve water that's why it's called the anti-diuretic hormone secondly there's oxytocin this one works hand in hand with prolactin while prolactin stimulates breast milk production oxytocin stimulates the release of breast milk it also works in the uterus because it helps stimulate contractors during labor now we'll move on to some of the other glands in the pituitary the thyroid gland is located at the base of your neck and it's shaped like a butterfly the thyroid gland controls how your body uses energy it controls our metabolism but also regulates several bodily functions including heart rate breathing and body weight the thyroid produces two important hormones triado thyronine called t3 for short in thrioxine called t4 those hormones come from the iodine and the food we eat when t3 and t4 enter our bloodstream they regulate how fast our cells and metabolism work for example these hormones determine how fast or slow our heart beats and the rate at which our intestines process food the pituitary gland along with the hypothalamus in the brain makes sure t3 and t4 are in balance if they're not that imbalance can cause health issues for example too much t3 and t4 can make you nervous and hyperactive too little can make you depressed tired and result in difficulty concentrating as small as the pituitary gland is it's a giant compared to the parathyroid glands these four glands are all the size of a grain of rice but their small size doesn't mean they have a small job you see the parathyroid glands regulate the body's calcium levels you've seen those commercials before the ones that say calcium builds strong bones well they're right the parathyroid glands store calcium in our bones where it's stored until other parts of our body need it the glands also control how much calcium our bodies absorb from our food and how much calcium our kidneys excrete now we've been in these situations before your palms get sweaty your heart races and it's all because of stress that's the adrenal glands springing into action the adrenal glands produce adrenaline the hormone that triggers the fight or flight response in humans and while that's what the adrenal glands are best known for they have other functions as well let's dive into the adrenal glands and their functions there are two adrenal glands and they both sit on top of your kidneys the adrenal cortex produces cortisol and aldosterone we covered cortisol the so-called stress hormone earlier in the video aldosterone has a direct effect on regulating blood pressure because it conserves sodium secretes potassium and retains water the adrenal cortex is located on the outer part of the adrenal gland every one of the hormones secreted by the adrenal cortex is vital to life the adrenal medulla which is the inner part of the adrenal gland produces several hormones including adrenaline the hormones produced by the adrenal medulla are not essential to life now we'll move to the male and female reproductive systems women have two ovaries that are critical to fertility the ovaries about the size of a large grape produce eggs that can be fertilized you might ask yourself why the ovaries are considered a hormone well it's because the ovaries secrete two hormones important to reproductive health estrogen and progesterone let's take a closer look at those hormones starting with estrogen estrogen plays a critical role in female growth development and childbearing there are actually three estrogens that all work together first there's estradiol estradiol helps the female reproductive organs grow the placenta produces estradiol which is why estradiol levels rise during pregnancy secondly there's estrone if any hormones has ever gotten a bad name it's this one estrone has been linked to moodiness and weight gain and is produced in a more prominent way during menopause lastly there's estral estradiol comes into play during pregnancy when the body releases the hormone into the bloodstream estradiol helps nourish the baby and the placenta after birth estrella levels in the body drop progesterone also plays an important part during pregnancy after ovulation progesterone helps get the uterus ready for a fertilized egg by thickening the uterine lining if there is no fertilized egg present the level of progesterone drops and then menstruation begins so those are the female hormones now let's talk about the male hormones the testes produce testosterone a hormone critical to the physical development of boys during puberty testosterone production results in several body changes including lower voice growing facial hair becoming taller and increasing muscle mass as men testosterone aids in sperm production maintains strength and mass and maintains sex drive that's our overview of the endocrine system it regulates several critical functions in our body including growth reproduction and stress hey guys welcome to this mometrix video about the urinary system of course we know the urinary system as one of the ways we expel liquid waste from our body but the urinary system regulates several other critical functions we'll go over a few of those roles in this video and give you more info on urinary system functions you may not know about the urinary system also known as the renal system has four primary parts the kidneys the ureter the bladder and the urethra the urinary system has a number of important roles including eliminating waste working with other organs so the body maintains a proper chemical and water balance and regulating blood volume and blood pressure we'll start by taking a detailed look at the kidneys the urinary system's primary organ we have two kidneys with one located on each side of our ribcage these two bean-shaped organs are about the size of our fist our kidneys regulate fluid balance in our body and eliminate waste from our blood they filter about 150 quarts more than 37 gallons of blood in a single day our kidneys have more than one million nephrons which are the kidneys filtering unit nephrons that filter blood remove waste and return the substances we need in our blood blood goes from the nephron to the malpigian body or as it's more commonly called the renal corpuscle the corpuscle has two structures that play a role in the filtering process the glomerulus pulls out protein from the blood and the bowman capsule takes the remaining fluid and sends it into the renal tubules the renal tubules in turn absorb a number of electrolytes into the blood including sodium chloride and potassium before the fluid continues its journey it becomes diluted and filled with the organic compound called urea remember that word urea because we're going to come back to it in a little while the kidneys need protection and that's where the renal cortex comes in the renal capsule surrounds the renal cortex and together surround the kidneys in our structures the renal medulla the inner and middle layer of the kidney contains renal pyramids and collecting ducts renal pyramids send fluid into the kidney and collecting ducts filter these fluids before we move on to the renal pelvis let's talk about a couple of the tubules in the kidneys the proximal convoluted tubule reabsorbs water glucose and other organic molecules back into the bloodstream here's where we're going to mention urea again the distal convoluted tubule removes urea and drugs from the blood and regulates the blood's ph levels then the fluid from the distal convoluted tubule enter the renal pelvis as urine then the urine progresses towards the bladder the renal pelvis contains calluses and hilum calyuses are like a collection bin that collect fluid before it makes its way to the bladder in the hilum the renal artery and renal vein each have an important part in filtering blood the renal artery supplies the kidneys with blood by carrying oxygenated blood from the heart to the kidneys the renal veins drain the kidneys by carrying filtered blood back to the heart that's an overview of the kidneys now let's take a look at the other parts of the urinary system the ureters are another part of the body's transportation system that pass urine from the kidney to the bladder half of the ureter resides in the abdomen while the other half resides in the pelvic area the ureters which are about 10 to 12 inches long in adults contain fiber muscle and mucus which make up the ureters thick walls there are two ureters that contract and relax pushing urine down into the bladder and on its eventual exit from the body if you've ever had a kidney infection that means the ureters didn't properly empty the ureters work a lot emptying urine into the bladder about every 10 to 15 seconds so if the ureter's regularly empty urine what happens in the bladder first the elastic-like bladder expands and then relaxes as it feels than empties urine the bladder is normally about two inches in length but when it's full can be more than triple in size to over six inches the human bladder can hold up to 24 ounces or three cups of urine but the bladder doesn't wait until it's full to empty we get the urge to urinate when the bladder is only about 25 full how does that happen the trigon a muscle sends a signal to the brain when it's time to be emptied the trigon also prevents fluid from backing up into the ureters now we'll discuss the urethra males and females each have a urethra and each has many similarities in some differences in both males and females the urethra carries urine from the bladder out of the body in males the urethra travels through the penis providing an exit for urine as well as semen thus playing a role in reproduction in females the urethra carries urine only and exits the body between the clitoris and the vagina we mentioned earlier that the urinary system also plays a role in reproduction and now you can see how there's another difference the male urethra is about eight inches long and the female urethra is about two inches long that shorter distance means bacteria have a shorter path from the urethral opening to the bladder which is why women get so many more urinary tract infections than men how prevalent are urinary tract infections in women one story showed that by the age of 32 at least half of all women had at least one urinary tract infection we mentioned in our opening that the urinary system plays an important role in regulating blood volume and pressure here's how that happens the body has a natural regulation system called homeostasis this regulation system maintains a set point that makes sure we don't get too far out of balance homeostasis for example makes sure your body temperature is always about 98.6 not exactly 98.6 but always around there in blood the urinary system filters out unwanted substances like excess fluids and maintains blood homeostasis the urinary system controls electrolyte and metabolite levels regulates blood ph and controls the blood volume and the pressure's osmoregulation you see osmoregulation controls the body's salt and water balance and this is where the kidneys come in again the kidneys filter out any excess water and waste maintaining that balance so that's our overview of the urinary system as you can see it does much more than empties waste from our system it's an important regulatory tool that plays a role in reproduction and filters waste hey guys welcome to this mometrix video about the immune system think of the immune system as the body's gladiator it fights for us defends us and protects us the immune system fights off pathogens the viruses and bacteria that seek to invade our body it defends us by sending out armies of disease-fighting cells when it senses an intrusion and the immune system protects us in natural and artificial ways let's take a look at how the immune system works all in an effort to help us stay healthy the lymphatic system fights infections and keeps the body's fluid levels balanced it protects the body from bacteria viruses and other pathogens the lymphatic system has a number of important components and we're going to take a look at five of them more in depth let's talk about lymph lymph contains white blood cells that help fight infection how exactly does lymph circulate lymph moves through our system to lymphatic ducts when the skeleton muscles contract lymph only moves in one direction unlike blood which circulates through the entire body there's a relationship between lymph and lymph nodes lymph nodes filter out harmful substances ensuring clean lymph gets placed back in the blood supply via the subclavian veins in the neck there are lots of lymph nodes in the human body as many as 700 of them and they're located in the neck armpit and groin lymph capillaries pick up lymph fluid that leaks from our bloodstream and into tissue before returning that lymph to the circulatory system lymph vessels carry lymph throughout the body now we know about these lymphatic systems the lymph the lymph capillaries lymph vessels and lymph nodes but what about the lymph tissue the lymph tissue which are rich in small white blood cells called lymphocytes protect the body from bacteria and other pathogens the tonsils adenoids thymus spleen and pears patches are all lymph tissues tonsils located in the pharynx filter out pathogens that can enter through the mouth or throat the thymus located in the back of the neck produces t cells an essential component of the immune system that seeks out and kills disease-carrying cells the spleen the lymphatic system's largest organ is the cleansing mechanism located under the ribcage the spleen takes dead blood cells and pathogens and removes them from the blood lastly pyrex patch located in the ilium of the small intestine protects the gastrointestinal or digestive tract from pathogens now we know how lymph tissue protects our body but those aren't the only protections there are general immune system defenses too even our skin is part of the immune system because it contains cells that can kill invading bacteria the ciliated mucous membrane acts like a venous fly trap catching dirt and other particles before it can enter the respiratory system glandular secretions destroy bacteria while gastric secretions or acids also destroy pathogens even bacteria itself helps defend the immune system normal bacteria populations battle with pathogens in the gut and vagina acting as a defense against harmful bacteria white blood cells also play a big part in our immune defenses there are five types of white blood cells that can be classified into two broad categories based on their structure granulocytes and agranulocytes granulocytes are a category of white blood cells that form in the bone marrow and play a role in fighting disease there are three types of granulocytes neutrophil is the quick strike team responding quickly to invaders basophil signals the body during invasion and eosinophil releases a substance that kills the pathogen agranulocytes are also formed in the bone marrow and are given their name because they do not have obvious granules in the cytoplasm there are two types of a granulocytes monocytes and lymphocytes lymphocytes include b cells t cells and natural killer cells and are more common in the lymphatic system than in the blood b lymphocytes or b cells make antibodies that specifically target bacteria and go on a search and destroy mission t lymphocytes or t cells are the attack force they attack and kill infected cells there are different types of t cells helper t cells play a critical role in regulating the immune system's response and they also stimulate b cells to make antibodies killer t cells kill virus and cancer cells while the memory t cells seem to have a mind of their own that's because memory t cells learn from their past encounters with infected cells and remember how to defeat them and then suppressor t cells stop the immune system's response after pathogens no longer pose a threat the last type of lymphocyte is the natural killer cells which bind to certain cells infected with cancer and viruses and kill them the natural killer cells identify cells that cannot be detected by the t cells monocytes the other type of a granulocyte are the largest and longest living phagocytes cells that act like pac-man and eat bacteria and other pathogens located in the lymph monocytes also alert t cells to the presence of those bacterial invaders monocytes eventually leave the bloodstream and become macrophages attacking microorganisms and removing dead cell debris white blood cells are also called leukocytes which are produced in the red bone marrow the home of the red blood cells platelets and white blood cells let's talk about antigens and antibodies and what happens when they enter our bloodstream an invader that enters our body typically is a protein from bacteria viruses or fungi is called an antigen when these antigens invade the antibody-mediated response kicks in and repels the invader antibodies are part of the response they can recognize antigens and counteract them we've already gone over quite a bit of information so let's do a short review of the immune system's steps there are five steps we'll look at it all starts with macrophages which engulf antigens and break them down next a helper t cell joins the macrophages then the body activates killer t cells and b cells and it's at that point that the killer t cells go on their search and destroy mission these killer cells look for and kill cells with the same antigen b cells then morph into plasma cells and memory cells the immune system contains two separate parts the innate immune system for general defense and the adaptive for more specific defense we're all born with an immune system that includes skin mucus and even ear wax that's the innate system which springs into action like a first strike force quickly attacking pathogens that have invaded our body here's an example you cut yourself opening a wound that can attract bacteria the innate system attacks and slows the bacteria the adaptive immune system is more selective attacking specific antigens by zeroing in on the intruders we noted earlier that memory t cells remember how to attack these invaders and these cells are a part of the adaptive immune system put another way the adaptive immune system has a react and prevent mode it reacts by killing invaders but it also prevents disease because of the antibodies production of b cells but how does the body fight against pathogens there are several ways both naturally and artificially natural forms of immunity come directly from our own bodies while artificial forms come from vaccinations let's take a closer look the body has a natural active and passive immunity let's take a look at naturally acquired active immunity when the body becomes infected with a pathogen it gets the disease but our body kicks into gear with an immune response that neutralizes the pathogen think of it as being exposed to an invader without an immunization the body also has a naturally acquired passive immunity that happens during pregnancy when antibodies go from the mother to child protecting the newborn through childhood then there are artificial means of building immunity you know all those vaccinations you get as a child that's a way of building artificially acquired active immunity on the other hand artificially acquired passive immunity is from antibodies that come from another individual or animal these immunizations provide quick protection during an outbreak or emergency so that's our overview of the immune systems the fighters within us that ward off disease and keep us healthy hey guys welcome to this mometrix video about this skeletal system every one of the systems in the body play a critical role in our ability to function but the skeletal system is particularly important without a skeletal system we wouldn't be able to walk and we would have no way to protect our vital organs like our heart and brain that's why the skeletal system and its network of 206 bones are so important to us the skeletal system has six main functions so let's talk about the skeletal system's main functions there are six of them and they're all important number one the skeletal system supports our bodies and the organs and tissues within it our skeleton gives us shape and holds us up so without a skeletal system we couldn't stand two the skeletal system gives us the ability to move the bones allow movement by acting like a kind of pulley when muscles contract they pull the skeletal bones which cause movement joints also play a critical part in movement because they determine flexibility so while you can bend your knee up to a 135 degree angle your back the thoracic spine only bends about 60 degrees at most the bottom line is this you need muscles bones and joints to move and bend and stretch three our skeletons protect our organs our skull protects our brain our rib cage holds up and protects our lungs and heart the spinal cord well that's protected by the vertebrae four and while those are some of the obvious ways our skeleton works for us there are some less obvious ones we need our skeletal system to produce blood cells there's a process called hematopoiesis that takes place in the skeletal system that's blood cell development both red blood cells which transport oxygen and white blood cells which fight infection in other words this is the process by which the body replenishes its blood system five not only that the skeleton axe is a storage system for the minerals calcium and phosphorus and we need both for our nerves muscles and body organs to function this results in an interesting tug of war within our own body you see the skeleton needs calcium and phosphorus to stay strong while at the same time distributing these minerals to other parts of the body that need them as well so if the skeleton shares too much of its mineral base it can become weak and lead to bone problems lastly the skeletal system is the main cog in the endocrine regulation which means it plays a big role in regulating energy metabolism this is a relatively recent finding since the research study wasn't published until 2007. the study showed bones release osteocalcin a protein hormone that regulates insulin productivity and sensitivity divisions of the skeletal system now that we know the skeletal system's six main functions let's look at the two parts of the skeletal system the axial skeleton and the appendicular skeleton the axial skeleton has 80 bones made up of the skull inner ear ossicles hyoid bone vertebral column and the ribs and sternum which is called the bony thorax taken together this means that the axial skeleton protects our central nervous system let's take a look at the axial skeleton in more detail the skull has 28 bones that protect our head and face and contains the cranial and facial bones each bone has its own function let's start with the cranial bones the cranial bones include the parietal the temporal frontal occipital sphenoid and ethmoid bones the two parietal bones are the flat bones on each side of your head located behind the frontal bone the temporal bones are located under the parietal bones these two irregular shaped bones are at the base and sides of the skull and house the ear structures then there's the frontal bone that's your forehead and it also contains the eye sockets the occipital bone is located at the back of the skull and it has an opening at the bottom it's from that opening that the spinal cord connects to the brain the sphenoid bone forms a large part of the base of your skull the ethmoid bone located in front of the sphenoid bone forms a part of the nasal cavity now let's look at the facial bones which have their own unique functions the facial bones include the maxilla the zygomatic mandible nasal palatine concha lacrimal and vomer bones the maxilla bone holds the upper teeth in place and forms the upper jaw the zygomatic bone despite the name is an easy one to remember because it's commonly referred to as the cheekbone the bone also forms the outer side of the eye socket the lower jaw bone called the mandible bone lets us open and close our mouth and chew since the bone houses our lower teeth the nasal bone is an easy one it's those two bones in the middle of our face that make up the bridge of our nose the palatine bone that's an l-shaped bone that forms the nasal and oral cavities the inferior nasal concha is a thin spongy and bony plate that forms the lower part of the nasal cavity's lateral wall the lacrimal bone is a small and thin bone actually it's the smallest and thinnest in the skull and it forms part of the eye socket and the vomer bone separates the left and right nasal cavity let's move on to the bones in our back the vertebral column has 33 bones and we'll describe them here the cervical vertebrae are the neck vertebrae that run right below the skull the cervical spine contains seven vertebrae each designated c1 through c7 the first two vertebrae have more specialized functions and each have their own name the c1 vertebrae called the atlas connects to the occipital bone and supports the base of the skull the c2 vertebrae called the axis allows the head to rotate the c3 c4 c5 and c6 vertebrae all have the same characteristics with a vertebral body arch and facet joints the c7 at the bottom of the spine connects with the top of the thoracic spine speaking of which the thoracic spine has 12 vertebrae located in the upper back the ribs connect to the thoracic spine and protect many of our vital organs and our spinal cord the thoracic cage itself contains the ribs and the sternum the lumbar spine has five vertebrae l1 to l5 located in the lower back where the spine curves in towards the abdomen the lumbar vertebrae support the weight of the entire torso and are most prone to injury the sacrum is a large bone made up of five fused a vertebrae at the base of the spine and is part of the pelvic cavity while the coccyx is made up of four small fused bones that can really really hurt if you fall on it most people know it as the tail bone so that's the axial skeleton the appendicular skeleton on the other hand has 126 bones that cover our arms legs hands feet our pelvic girdle and our shoulder girdle that means the appendicular skeleton governs movement the appendicular skeleton can be subdivided into four areas the pectoral girdle covers the clavicle in scapula which connects the upper extremities to the trunk the clavicle is commonly known as the collarbone and the scapula as the shoulder blade the upper extremities that's your arm includes the humerus radius ulna carpals metacarpals and phalanges the pelvic girdle your hip bone serves as the attachment mechanism for the lower limbs the lower extremities or your legs cover the femur tibia fibula patella tarsals metatarsals and phalanges skeletal functions so as we can see the skeletal system controls movement and protects our vital organs not only that relatively new research shows how the skeletal system plays a role in regulating energy metabolism now let's take a look at the bones that place such an important part in the skeletal system skeletal system components we know that the skeletal system is made up of bones but what exactly are bones and what other functions do they have bones are connective tissue and some bones are more rigid than others that's why bones have two classifications one there are compact bones which are dense and rigid and make up much of the skeleton's hard structure compact bones are stronger they support the body protect vital organs and are the engine that power movement compact bones also release calcium and phosphorus into the body when it needs it the body's long bones like the tibia femur and fibula are examples of compact bones two cancellous bones are located within the compact bones they're softer and spongier which is why these bones are often called spongy bone what do they do they control the production of red blood cells and you'll also find nerves in bone marrow in this spongy bone both compact and spongy bone is found in most bones compact bone is the outer shell around spongy bone bone also comes in different shapes and each with their own purpose the flat bones like the sternum and cranium protect organs the long bones like the femur and tibia support weight the cube shape short bones like the carpals in your hands and tarsals in your ankle provide stability the irregular bones like the ones of the vertebrae and pelvis protect organs lastly the sesamoid bones are small round bones embedded in the tendons such as the kneecap which protect tendons from stress and wear so that's our overview of the skeletal system the bones that help us walk protect our internal organs produce blood cells and help with insulin productivity and sensitivity hey guys welcome to this mometrix video over the nervous system all systems and parts of the body are important but the nervous system is a system that has its fingers and everything your body does it's a system that literally controls every process within your body the nervous system includes anything within the body that would allow you to sense so the brain spine and spinal cord all nerves and any other sensory neurons the nervous system has four main roles or functions first to collect and receive information internally and externally so from within the body and outside of the body second to process or derive meaning from the information collected and received third after the information has been processed the nervous system forwards that information to the appropriate party so to the muscles organs or glands this information sets them up to react how they need to and fourth the nervous system dispatches the information to the regions of the brain that handle processing of the information the nervous system just like every other structure and makeup of our bodies is very ordered and systematic you can think of the nervous system as having two main divisions and then several subdivisions that fit within those two divisions the two divisions of the nervous system are the central nervous system and the peripheral nervous system first we'll take a look at the central nervous system and what exactly that includes the main function of the central nervous system is to incorporate the information it is getting and systemize the information so that it can cue a proper response the central nervous system is composed of the brain and spinal cord these two components encompass several other components so we'll take a closer look at the brain first the brain has six different regions the cerebellum the cerebrum the medulla the brain stem the thalamus and the hypothalamus the cerebellum sits right behind the upper portion of the brainstem which is where the brain and spinal cord connect and consists of two half spheres or hemispheres the cerebellum is the region of the brain that coordinates movement and where various features of motor learning take place in other words the cerebellum is the part of your brain that allows for balance coordination speech and posture as well as things like muscle memory the cerebrum sits in the top portion of the cranial cavity the cerebrum is separated into a left and right hemisphere by a trench like line called the longitudinal fissure and the right half manages the left side of the body the left half of the cerebrum manages the right side of the body however even though there is a groove that distinctly separates the two halves of cerebrum there is a bundle of neural fibers called the corpus callosum that connects the two halves and allows them to work together the cerebrum is made up of four different lobes the frontal lobe the temporal lobe the perito lobe and the occipital lobe the frontal lobe like its name suggests is at the front most region of the brain and out of the four lobes is the biggest the frontal lobe is split from the periodical in the temporal lobe by fissures the fissure that separates it from the periodic lobe is called the central sulcus in the fissure that separates it from the temporal lobe which is even deeper is called the lateral sulcus the frontal lobe contains the primary motor cortex the primary motor cortex or m1 is one of the main components of the brain included in the body's motor function the primary motor cortex initiates electrical signals and impulses that initiate body movement the frontal lobe is also essential for problem solving speech and articulation and it's accountable for personality traits the temporal lobe you actually have two temporal lobes one for both hemispheres your temporal lobes are located near your ears and they mainly function in auditory processing the temporal lobe taps into other roles as well such as visual memory your ability to learn language and emotion association perito lobe the periodical lobe is set between the occipital lobe and the frontal lobe the periodic lobe has a really big job of having to process the information that it receives within milliseconds the somatosensory cortex is located inside of the periodical lobe and is crucial for processing the information from touch the somatosensory cortex allows us to pinpoint the exact locality of a touch perception and helps to distinguish pain levels and temperature the periodontal lobe is important for a depth of perception and communicates with other parts of the brain in order to perform other tasks occipital lobe the occipital lobe sits in the back part of the cortex the main function of the occipital lobe is to process visual information from the eyes and relay that information the occipital lobe has to very quickly process that information so that we are able to respond accordingly that's an overview of the cerebrum now let's take a look at the medulla more officially known as the medulla oblongata the medulla is a section of your brain stem and remember your brain stem is where your brain and spinal cord connect the medulla is one of the three parts of the brain stem the medulla has immediate control over numerous autonomic nervous system responses it aids in the control of particular regions of the body and it also plays a role in motor functions and outward motion the medulla is very important just like every other part of your brain the medulla helps control breathing and it controls our heart rate the medulla functions involuntarily the medulla responds to various heart functions by dilating the blood flow so that there is a higher or lower amount of oxygen circulation it can help by responding in fight or flight situations by switching digestion on or off causes us to cough or sneeze to get rid of unwanted particles that get into your nasal cavity and controls vomiting or swallowing in order to dispel anything that may bring harm to you the fourth region of the brain that we'll look at is the brain stem the brain stem has three different parts the medulla which we just talked about pawns in midbrain the pawns sort of function as a message headquarters for many other parts of the brain it aids in communication between brain sections like the cerebrum and the cerebellum the pons is right above the medulla and beneath the midbrain so it sits right in the middle many essential nerves stem from the pons the nerve permits sound to proceed from our ears into our brain the abducens nerve permits the eyes to move and look horizontally the trigeminal nerve allows for us to experience filling in the face and the facial nerve allows for us to actually make facial expressions the pons helps in the duties of the medulla and it is linked to managing our sleep cycles now the midbrain is called the midbrain because it sits between the forebrain and the hindbrain but it's important to note that out of the three parts of the brainstem it is not located in the middle the midbrain functions like the medulla and is the super message headquarters between the forebrain or cerebral cortex and the hindbrain or the cerebellum and brainstem the midbrain allows you to incorporate sensory data coming from your eyes and ears with data coming from your body's muscle movements helping it to adjust your movements based on important information all three parts of the brain stem function involuntarily the thalamus is the fifth region of the brain the thalamus sits right above the brain stem sandwiched between the midbrain and the cerebral cortex the primary job of the thalamus is to inform the cerebral cortex of any sensory or motor stimuli the thalamus also helps to control sleep and aids in keeping us awake and alert the thalamus along with the hypothalamus epithalamus and subthalamus is a part of the diencephalon also sometimes called the interbrain the diencephalon is the area where the vertebrate neural tube is located which helps bring about the formation of the forebrain the sixth and last region of the brain is the hypothalamus the hypothalamus is positioned below the thalamus and is the bottom part of the diencephalon one of the main functions of the hypothalamus is that it connects the nervous system to the endocrine system which allows the hypothalamus to regulate our body's temperature the hypothalamus also aids in certain metabolic processes and helps to regulate the autonomic nervous system that was a closer look at the brain itself the spinal cord is the other component that makes up the central nervous system the spinal cord administers motor data coming from our brain to the appropriate parts of our body and helps to perform slight reflexes it also administers sensory data directly from the peripheral nervous system to the brain the spinal cord consists of 31 pairs of spinal nerves because each of these nerves include motor and sensory axons they are referred to as mixed nerves so that was the central nervous system the second main division of the nervous system is the peripheral nervous system or pns the peripheral nervous system is made up of nerves and what are called ganglia nerves are bundles of nerve fibers also known as axons there are two types of nerves in the peripheral nervous system spinal and cranial nerves like i've said there are 31 pairs of spinal nerves but there are 12 pairs of cranial nerves ganglia refers to a cluster of neuron somas or cell bodies the individual cell body attached to dendrites the dendrites send information to the neurons the axons or nerve fibers then communicate that information to other neurons it's all a connected web these nerves and ganglia are located around and outside the brain and spinal cord the primary function of the peripheral nervous system is to link the central nervous system to the body's organs and appendages thus acting as the primary messenger between the brain spinal cords and everything else in the body you can kind of think of the peripheral nervous system as the system that helps our brains and bodies to understand the world around us the peripheral nervous system has two subsystems the somatic nervous system and the autonomic nervous system the somatic nervous system is the part of the peripheral nervous system that is linked to voluntary bodily movements it contains two parts the sensory nervous system as well as the somatosensory system which is part of the sensory nervous system the sensory nervous system is responsible for processing as you might guess sensory data the most familiar sensory systems are the ones that control touch taste smell hearing and vision now the somatosensory system focuses on conscious recognition of temperature pain touch pressure movement position and any sort of vibration the somatosensory system communicates different sensations identified near the vicinity of the body through the spinal cord then the brain stem and up to the sensory cortex located in the periadolope the sensory nervous system contains sensory neurons or afferent neurons and motor neurons or efferent neurons afferent neurons transmit stimuli to the central nervous system as opposed to transmitting them from the cns efferent neurons in response to the afferent neurons transmit signals from the central nervous system to the rest of the body the transmission of stimuli through afferent neurons to the cns and then from the cns to other parts of the body allow for us to perform voluntary body movements as well as moderate involuntary reflex arcs the autonomic nervous system is the other part of the peripheral nervous system that manages involuntary movements and functions involuntary meaning that these movements happen without us being consciously in control of them happening the autonomic nervous system also communicates information to our internal organs there are two main divisions within the autonomic nervous system the sympathetic nervous system and the parasympathetic nervous system the sympathetic nervous system is the system that gets our body ready for the reaction that has been familiarized as the fight or flight response when our body is being threatened or at risk for potential injury this is the system that controls our response the sympathetic nervous system causes our bodies to become keenly alert speed our heart rates causes muscle contraction and shuts off any function that is not essential for survival the overall functioning of the sympathetic nervous system is largely due to the neurotransmitter acidic choline the neurotransmitter binds to nicotinic receptors to trigger the release of norepinephrine which is produced by the adrenal gland to prepare our body and brain for action nicotinic receptors are the main receptors in the muscles for motor neuron to muscle correspondence that manage the contraction of muscles the sympathetic nervous system originates in the thoracic and lumbar regions of the spinal cord the parasympathetic nervous system which is the other part of the autonomic nervous system manages the body's function when at rest rest in digest is the phrase given to reference the response of the parasympathetic nervous system the parasympathetic nervous system works to conserve homeostasis within the body it does the opposite of the sympathetic nervous system and instead relaxes the body's muscles and slows our heart rate its job is to restore everything to a state of relaxation and balance the parasympathetic nervous system increases bowel movements and urinary output the neurotransmitter acetylcholine also plays a huge role in the parasympathetic nervous system by binding to muscarinic receptors allowing the contraction of smooth muscles this is what allows the parasympathetic to slow down the heart rate regulate digestion and relax muscles the parasympathetic nervous system originates in the sacral portion of the spinal cord it's important to note that both the central and peripheral nervous system enlist the acidic choline receptors both nicotinic and muscarinic we just covered a lot of information but here is a very very generalized diagram of the nervous system to help you remember the main parts you start with the nervous system itself then you have the two main divisions the central nervous system which includes the brain and spinal cord and the peripheral nervous system which is made up of nerves and ganglia the peripheral nervous system then has two subdivisions the somatic nervous system which controls voluntary movement and the autonomic nervous system which controls involuntary movement then both the somatic and autonomic nervous system contain two subdivisions the somatic nervous system contains the sensory nervous system and the somatosensory system which is part of the sensory nervous system and lastly the autonomic nervous system contains the sympathetic nervous system which controls our fight or flight response and the parasympathetic nervous system which controls our rest and digest response if all of these systems seems pretty interconnected the answer is yes welcome to this video overview on the integumentary system also known as the skin in this video we'll talk about the different layers of the skin the skin's role in maintaining temperature homeostasis of the body and sebaceous and sweat glands the english word integument comes from the latin word integumentum which means a covering the integumentary system is broadly defined as being composed of the skin and its accessory structures but the terms integumentary system and skin are often used interchangeably accessory structures are also called specialized derivatives because of their biological origin and include hair nails and glands of the skin because skin is made up of various structures that participate in related functions it can be considered an organ and is the largest organ in the human body by mass the top layer of the skin that faces the external environment is called the epidermis the epidermis is made up of keratinized stratified squamous epithelium keratinocytes are a type of cell present throughout the epidermis that produces and stores keratin which is a protein that gives skin hair and nails their hardness and ability to resist water stratified refers to the multiple layers of cells in the epidermis and squamous refers to the cell's flattened shape an epithelium is a type of tissue that forms a barrier between the internal and external environments and regulates the flow of substances into and out of the body the epidermis is further divided into four or five layers depending on its location on the body the outermost layer called the stratum corneum is made up of dried keratinized cells that eventually slew off and are replaced by cells in the layer beneath it and the palms of hands and soles of the feet the layer that follows is a clear thin translucent layer called the stratum lucidum underneath the stratum lucidum and the palms and soles and directly under the stratum corneum in all other areas of the skin is the stranum granulosum the stratum spinosum underlies the stratum granulosum and also contains langerhans cells which break down foreign particles in damaged cells the most internal layer of the epidermis is the stratum basale which is made up of basal cells that divide to produce keratinocytes and push other cell layers towards the top also present in the stratum basale are melanocytes which are responsible for skin and hair color and merkel cells which are receptors for sensing touch below the epidermis is the layer of skin called the dermis the dermis is composed of connective tissue that gives skin strength and structure blood and lymph capillaries present in the dermis bring oxygen and nutrients to the skin and remove waste the dermis is also divided into two layers the top layer of the dermis called the papillary dermis forms small projections into the adjacent stratum basale of the epidermis and is responsible for the visible unique skin patterns such as fingerprints and footprints collagen in the papillary dermis forms loose connective tissue the larger lower layer of the dermis is called the reticular dermis and is primarily composed of collagen elastin and reticular fibers that form dense connective tissue the reticular dermis also contains hair follicles sebaceous glands and sweat glands both sebaceous and sweat glands are exocrine glands meaning they secrete products to the outside of the body sebaceous glands are groups of cells that produce an oily substance known as sebum which is thought to lubricate the hair and contribute to water resistance of the skin most sebaceous glands empty into a hair follicle which subsequently leads to the surface of the skin sebaceous glands are present in the dermis all over the body except the palms and soles varieties of sebaceous glands and sebum serve specialized functions in different locations in the body for example sebum mixes with other secretions on the surface of the eye to keep it lubricated and clean and in the ear canal to produce cerumen commonly known as earwax during fetal development sebum accumulates on the skin and contributes to the vernix cassiosa sebaceous glands are highly responsive to hormones and their size and activity are small during infancy and childhood but increases during adolescence a greater production of sebum is one factor that can contribute to acne cyboric dermatitis and other skin conditions there are two main types of sweat glands ekron sweat glands which empty their secretions into the ducts that open at the surface of the skin throughout the body and apocrine sweat glands which empty into hair follicles in certain areas like the axolyte in perineal region echoing glands produce the familiar thin watery salty secretion known as sweat in response to emotional stress or elevated internal or external temperatures as sweat travels up to the pore much of its salt content is reabsorbed resulting in sweat containing about half of the salt content of plasma this reabsorption of salt is interrupted in patients with the genetic disorder cystic fibrosis leading to excessively salty skin epicrin glands produce a more oily substance that mixes with sebum as it exits to the surface of the skin similar to sebaceous glands apocrine glands are responsive to hormones and are largely inactive until puberty apricorn sweat is odorless but can react with bacteria on the skin's surface to produce body odor additionally mammary glands are thought to be specialized apocrine sweat glands that are modified to produce milk although not technically part of the skin the subcutaneous tissue directly underneath the dermis is often included as the innermost layer of the skin also called the hypodermis it is composed mostly of adipose tissue and functions as fat storage cushioning and insulation for the body the human body produces its own heat and regulates its own temperature heat is generated in the body mainly through metabolism but sometimes through muscle activity as well such as exercising or shivering heat transfers from warmer objects to cooler ones by radiation conduction convection or evaporation the skin plays a crucial role in maintaining the body temperature at a consistent level blood vessels in the dermis can either dilate to allow more blood to get closer to the surface of the skin to release heat or constrict to keep blood towards the inner body and preserve heat in addition the production of sweat by acronym glands allows for heat loss through evaporation pilo erection colloquially known as goosebumps or goose pimples is caused by the contraction of the erector pili muscle which is connected to the hair follicle upright hairs have the potential to trap warm hair close to the skin and preserve heat although this effect is minimal in humans with sparse body hair male and female reproductive systems have many common anatomic and physiologic features for example in men a penis and scrotum develop while in women clitoris and labia develop the primary sex organs the testes and ovaries are referred to as gonads the primary purpose of both the male and female reproductive systems is just that reproduction let's look at the male reproductive system first the external genitalia consists of the penis and the scrotum which contains the testes the appearance of the penis varies slightly depending upon whether the male is circumcised or uncircumcised the penis consists of the shaft the glands which contains the urethral opening and the corona which is the base of the glands in a circumcised male the glands is exposed but in an uncircumcised male the glance is covered by the foreskin which retracts during an erection the average length of a flaccid penis is about 3.5 inches and the average length of an erect penis is about 5 inches the primary sex organs of the male reproductive system are the testes which produce the sperm cells or spermatozoa the other internal reproductive organs and the external genitalia comprise the secondary sex organs the scrotum is a sac-like structure that hangs free from the body this allows air to circulate about the scrotum to maintain the temperature about 2 degrees centigrade below body temperature because sperm are immobile at body temperature the reproductive system also includes two testes which are suspended by spermatic cords and are contained within the scrotum the spermatic cord consists of the vas or ductus deferens blood vessels lymphatics and nerves the testes are oval shaped approximately 3.5 by 5.6 centimeters in size each testis is encased in a tunica albuginea or a tough fibrous capsule septa divide each testis into about 250 lobules these lobules contain one to four tightly coiled seminiferous tubules which come together to form the epididymis the seminiferous tubules contain specialized cells that produce sperm and others that secrete male hormones the tiny tubes that form the epididymis are about six meters long and merge into the vas deferens also known as the ductus difference at the tail end the sperm that form in the seminiferous tubules are non-motile and immature when they enter the epididymis but the rhythmic contractions that cause the sperm to move through the epididymis also cause the sperm to mature so they become motile on ejaculation the sperm passed through the vast difference which becomes part of the spermatic cord which then passes through the inguinal canal into the abdominal cavity and into the pelvic cavity near the end the vast difference merges with the ducts from the seminal vesicles to become the ejaculatory duct the seminal vesicles are about five centimeters long and secrete nutrients hormones and an alkaline fluid that controls the ph of the semen these substances increase the volume of the semen the ejaculatory duct passes through the prostate gland and empties into the urethra the prostate gland which is chestnut shaped and about four by three centimeters in size wraps around the urethra right below the bladder the prostate gland secretes a milky alkaline fluid that neutralizes the semen and increases the motility of the sperm cells this fluid empties directly into the urethra as the contents of the ejaculatory duct vesicles enter the urethra further increasing the semen volume beneath the prostate gland the two bubble urethral grants are about one centimeter in diameter and secrete a mucus-like substance into the urethra to lubricate the glands of the penis the penis contains three columns of erectile tissue two corpora cavernosa on the dorsal surface and a single corpus spongiosum which contains the urethra on the ventral surface during sexual stimulation the vasodilator nitric acid is released causing the arteries of the penis to dilate and increasing the flow of blood to the erectile tissues the increased pressure from the arterial blood flow decreases venous drainage further causing the penis to swell and elongate so that it becomes rigid enough for penetration into the vagina during sexual intercourse the fluid that is ejaculated through the urethra is semen and the typical volume of an ejaculation ranges from two to five milliliters containing about 120 million sperm while sperm can live for weeks and ducks in the body it can generally survive no more than three to five days after ejaculation now let's talk about the female reproductive system the primary sex organs of the female reproductive system are the ovaries which produce the eggs or ova the other internal reproductive organs and the external genitalia comprise the secondary sex organs the external genitalia include the vaginal opening labia menorah and labium majora which provide protective lips around the vagina and the clitoris which provides sensation during sexual activity the clitoris is a complex structure located externally above the urethra the labia minora provide a hood about the glands clitoris which is the visible part of the clitoris however most of the clitoris is embedded in the tissues the gland's clitoris is very sensitive to touch because of a high concentration of nerves behind the visible glands the body of the clitoris splits into two halves each containing accuse or elongated part and a vestibular bulb also known as a bartholin gland the crura which are each comprised of two corpora cavernosa similar to the penis are located behind the labia menora and the vestibular bulbs are located on either side of the vagina both the acrora and the vestibular bulbs contain erectile tissue the vestibular bulbs secrete mucus which provides lubrication similar to the bulbourethral glands in the male the vagina is about 3.5 inches long and is a fibromuscular tube that extends from the vaginal opening or orifice to the uterus the vaginal opening is covered by a thin membrane called the hymen the hymen has a central opening to allow for drainage of vaginal secretions and menstrual fluids the hymen typically stretches or tears during physical activities or sexual intercourse after the hymen is broken it does not grow back or require repair as it appears to serve no real purpose and is unrelated to virginity despite a common misperception when a female nears an orgasm the lower third of the vagina becomes engorged with blood and swells and this increases friction on the penis during intercourse in order to promote ejaculation the cervix is the lower end of the uterus and connects the vagina to the uterus through a short canal during sexual stimulation the cervix dilates slightly the contractions that occur with orgasm promote the movement of sperm through the cervix and into the uterus and onto the fallopian tubes the uterus is typically located behind and above the bladder and in front of the colon it's a pear-shaped hollow muscular organ that is about 7.5 centimeters by 4.5 centimeters and 3 centimeters wide in its normal state but expands greatly with pregnancy the ovaries the primary sex organs are solid oval-shaped structures they're about 3.5 centimeters by two centimeters and one centimeter thick and lie on each side of the pelvic cavity and are held in place by ligaments the outer part of an ovary is the cortex and the inner part is the medulla the ovaries produce the hormone estrogen when a female is born each ovary contains about one million primordial follicles which consist of a primary oocyte also called an egg or ovum and a layer of follicular cells more than half of these primordial follicles degenerate before puberty and this process of degeneration continues with only a few hundred released over the course of a female's life during puberty maturation continues and the primary oocyte matures into a secondary oocyte or ovum and eventually ruptures through the ovary with ovulation the corpus luteum forms the remains of the ruptured follicle and secretes hormones and then degrades into the corpus albicans fertilization of an opium occurs within the fallopian tubes also known as the uterine tubes or oviducts when a sperm enters the ovum the fallopian tubes which are about 12 centimeters in length provide a connection between the ovaries and the uterus so that a fertilized egg can travel to the uterus for implantation the funnel-shaped infundibulum at the end of a fallopian tube near the ovary contains a number of extensions called fimbriae one of which connects directly to the ovary the fimbriae help draw the ovum into the fallopian tube the mammary glands or breasts are accessory organs of the female reproductive system each breast contains 15 to 20 lobules that contain alveoli or milk glands the alveoli produce milk after childbirth and ducts lead from the alveoli to the nipple the nipples and areola about the nipples are very sensitive to stimulation and tend to swell during sexual arousal although this is caused by muscle fibers as the breasts do not contain erectile tissue the small projections on the areola are the areolar glands or montgomery's tubercles which produce a nipple lubricant the primary purposes of the male reproductive system are to produce sperm transport the sperm to the female reproductive tract and secrete hormones the primary purposes of the female reproductive system are to produce ova secrete hormones and provide for the protection and development of a fetus that's all for now thanks for watching and happy studying