hello everyone now we start studying the respiratory system and these are our learning objectives the respiratory system has several functions and one of them is the one that we usually remember that in goes the good air and out goes the bad air so we have oxygen going into our body and we eliminate carbon dioxide we need oxygen because of cellular respiration and the oxygen is used to make ATP and carbon dioxide is a waste product generated in cellular respiration as you make ATP so you need the air reaching oxygen to get in in the air reaching carbon dioxide to get out in this action of air going in and out of our lungs is what we call pulmonary ventilation you need to think like it vents and when you say something is venting it's releasing air right so it's like moving air around so pulmonary ventilation is related to the air coming in and out of our lungs this function of the respiratory system is intimately linked to the cardiovascular system because we have the blood moving through our lungs to get oxygen so we can use this oxygen to make ATP now another function of our respiratory system is related to olfaction so the fact that we can ismael something is related to the respiratory system and lastly another main function of our respiratory system is related to vocalization so the fact that we are able to communicate is also related to our respiratory system we can divide the respiratory system in two sections the upper respiratory system and the lower respiratory system the upper respiratory system includes the nose nasal cavity nasal conchae paranasal sinuses and the nasal pharynx so when we have an upper respiratory infection the respiratory infections using one or more of these areas so it's closer to the surface of our body now the lower respiratory system includes larynx trachea bronchi and then we have the bronchi dividing several times and with each division the bronchi gets thinner and thinner and thinner until it divides into bronchioles now looking at this diagram we can see that our right lung is bigger than our left lung and the reason for that is that our heart is shoved into the left side of our thoracic cage here we have a picture of a cadaver showing how the heart fits in between the lungs since the heart is a slightly shifted to the left we have one last lobe in our left lung and the place in the left lung where the heart fits in is called cardiac notch so we have two lobes in the left lung and three lobes in the right lung and these lobes are separated by fissures in the left lung since we have just two lobes we have just one fissure we have the oblique fissure separating the superior and inferior lobes of our left lung now our right lung has three lobes the superior the middle and the inferior lobes and separating the superior and the middle lobes we have the horizontal fissure and separating the inferior from the other two lobes we have the oblique fissure when we study the heart I mentioned the heart was located in the mediastinum so the area in the middle of the sternum now this medial surface of the lungs that face the heart is called mediastinal surface the surface of our lungs that faces the ribcage is called costal surface in the surface of the lungs that is in contact with the diaphragm is called diaphragm surface now our lungs are like a spongy type of tissue and if we could feel a long you'd notice that it feels like one of those fancy mattresses that when you press your hand you leave an indentation and then it slowly the indentation is starting disappearing until the mattress looks flat again so if you squeeze the lungs it retracts and is lonely it starts going back to the resting shape in the opposite is also true so if we stretch the lungs it would recoil back to a resting shape and that's because of the internal elasticity of our lungs so if you think of that we can ask ourselves what's keeping the lungs inflated if it has attendants to retract and what keeps our lungs inflated is the pleura here we can see a cross-section of the thoracic cavity and you can see that we have a space between the lungs and the thoracic wall in this space is where we find the pleural cavity we have the right pleural cavity surrounding the right lung and we have the left pleural cavity surrounding the left lung so if you recall when we talked about the heart surrounding the heart we had the serous membrane of the pericardium which was composed of the visceral pericardium and the parietal pericardium in between those two layers we had the the pericardium fluid similarly here in the lungs we have the pleural membranes we have the visceral pleural membrane right in contact with the surface of the lungs and we have the parietal pleura membrane in contact with the thoracic wall and between these two membranes we have the pleural fluid with these lipid serous fluid secreted by the simple squamous epithelial cells that make up the visceral and parietal layers of the pleura so the parietal pleura membrane attached to the inner wall of our chest and the visceral pleural membrane attached to the surface of our lungs and then they prevent our lungs from collapsing now this lipid fluid found in the pleural cavity between the parietal and visceral layers act as a lubricant and then it allows the two pleural membranes to is lined against each other during respiratory movements so since the pleural membranes are what a deer they long to the inner thoracic wall and with that our lungs are actually held to the wall of our thoracic cage that's what keeps our lungs inflated now if the pleura gets damaged you can guess how bad that gets when air enters either the right or left pleural cavity so the space between the pleural membranes air it starts to flow into the chest and the lungs will pull away from the chest wall and that results in either a partial or complete collapse of the lung and this is clinically called pneumo taric's literally air in the Tharks now the way this is treated is by actually inserting the needle office syringe into the pleural cavity and then trying to aspirate the air into the syringe and as the air is drawn back into the syringe and out of the pleural cavity the log ring fleet and reattached to the chest wall so that's the importance of this pleural fluid in between the two pleural membranes so in terms of functional anatomy we can differentiate the respiratory system into the conducting zone in the respiratory zone so the conducting zone as the name implies has the job of conducting the air until it reaches the respiratory zone which is the place where the actual gas exchange happens and as you can imagine the place where the gas exchange happens needs to be very thin thin enough so the gases can just move across via diffusion however in the conducting zone we have part that are very exposed to the external environment and as you go down into your lungs it starts being less and less exposed to the outside environment so with that in mind you can expect a gradual change in the respiratory epithelium as you go from areas that are more externally exposed to areas really deep inside their lungs where the gas exchange happens if we look at the air through a beam of light we can see several little dust particles floating around and we are actually inhale all that so we need to clean the air before it goes deep into our lungs and in order to clean the air that we inhale we have a ciliated mucous membrane lining basically the entire conducting zone of our respiratory tract with the exception of the oral pharynx and there are Inga pharynx the oral pharynx and the laryngopharynx are lined with a stratified squamous epithelium so we have several layers that's defined by the stratified world right of squamous cells so oral pharynx and laryngeal fairings are lined with stratified squamous epithelium but all the rest of our conducting zone so the inside lining from our nasal cavity all the way down to the Broncos we find pseudo stratified ciliated columnar epithelium with goblet cells and this is the anatomical name for what I said before ciliated mucous membrane so since we are in an anatomy class you guys need to know the anatomical name so the name again is still do a stratified ciliated columnar epithelium in to refresh your memory when we say still be stratified it means that it looks like it has more than one layer but the still the root means it's not true right so the still the stratified epithelium looks like it has several layers but in reality it's formed by a single layer of columnar cells and in the echo surface of these cells we find cilia so if you look here at this magnified version of the respiratory epithelium we can see the goblet cells which are labeled here as mucous cells and the goblet cells are the ones responsible for secreting the mucous at which the particles and pathogens will get stuck to and then we have the particles in the air that we hail'd trapped in mucus in this cilia all these cilia that we see right here that are inside the mucus they move in a specific direct and with that they move the particles that were stuck in the mucus towards our throat and we swallow it and then all the dirty particles and possible pathogens that were present in there we inhaled now go to our stomach and they get destroyed by the acid of our stomach so as you can conclude this mucus layer that we have inside our respiratory tract that traps all the inhaled those particles and pathogens it works as a respiratory defense system right so basically throughout the entire conducting zone of our respiratory system we have this mutual ciliated membrane that traps the debris and pathogens that were present in the air we inhaled but besides this cleaning function of the conducting zone the conducting zone also warms and humidifies there we inhale so if you put your hands in front of your mouth and you exhale you can feel that the air you are exhaling is warm and if you go in front of a mirror and you blow on it you can see that the mirror gets foggy and the only reason why the mirror gets foggy is because the moisture present in the air we exhale condensed on the mirror so it's important to warm the air that we are inhaling because we are often exposed to a Tim aspheric air that's much colder than our own body temperature and for example if we are in a very cold environment we do not want that cold air getting all the way down into our lungs where it could potentially freeze our lungs so we need to warm the air that we are inhaling and also we need this air to get humidified because humidification protects cells against the hydration so if we hail'd really dry air that did not get humidified it could dehydrate the membrane lining the inner side of our respiratory tract and that could damage the cells of our respiratory tract when we hear you through our nose the air passes through our nostrils also called external nares and then they are passes the nasal vestibule which is this part at the beginning between the nostrils and the nasal cavity the nasal vestibule is supported by hyaline cartilage that we have at the tip of our nose and that's why the tip of our nose is kind of bendable at the nasal vestibule we find hairs that extends towards or nostrils in these hairs found in ear at the needs of vestibule work as strainers inhibiting large particles from getting into our nasal cavity now after there passes through the nasal vestibule there reaches the nasal cavity and we have the right and left nasal cavities in the wall we have separating the right and left sides of our nasal cavity is called nasal septum and it is formed by the perpendicular plate of the ethmoid bone fused to the vomer bone in forming the interior portion of our nasal septum we have hyaline cartilage and that what confers the flexibility of our nasal septum when air reaches the nasal cavity the air encounters some speed bumps which are the nasal conchae we have the superior middle and inferior nasal conchae working as speed bumps creating turbulence in the air we just inhaled and this turbulence makes their move around and with that dust particles and pathogens that were present in the air we inhaled get stuck in the mucus and the air gets cleaned warmed and humidified before it follows its path to our lungs so if we did not have this bumpy surface if instead we had a very smooth surface the air we would inhale would just flow very nicely through the nasal cavity and follow the pathway down to our lungs and that would not be very helpful so the presence of these elevations obligate the air to move around in this moving motion warms and humidifies there and help with the dust particles and pathogens getting stuck to the mucus now besides this turbulence created by the nasal conchae to help us clean warm and humidify there this turbulence also helped us to ismael better so due to the turbulence we have odorant molecules getting trapped in the mucus and with that these chemical molecules end up binding the olfactory receptors present at the olfactory epithelium on the superior surface of our nasal cavity hence the turbulence created by nasal conchae aids in the process of his mouth now after there's rolls around in the nasal cavity it keeps moving backwards and after the air passes an area called posterior nasal aperture the air reaches the pharynx and the pharynx is shared by the digestive and respiratory systems and it is divided into three sections the nasal pharynx the oral pharynx and the laryngopharynx the portion of the pharynx that's close to our nose is called nasal pharynx the portion of the pharynx that's close to our oral cavity is named oral pharynx and the portion that's closer to our larynx is called laryngopharynx so it all makes sense now right at the back of our nose as I just said we have the nasal pharynx and if you recall when we talked about our ear I mentioned that we had the auditory tube and this tube was responsible for equalizing the pressure on both sides of the tympanic membrane and this tube opened up and the nasal pharynx and here you see it this opening of the auditory tube receives the name of pharyngeal opening of the auditory tube because it opens in the pharynx now if you look here separating our nasal and oral cavities we have these two structures the hard palate followed by the soft palate and the hard palate is made by the maxilla and the Palatine bone and the soft palate is soft and it moves up and close our nasal passage when we are swallowing the soft palate is what designates the line that separates the nasal pharynx and the oral pharynx and a very interesting thing is that the epithelium changes when it crosses from the nasal pharynx to the oral pharynx in the nasal pharynx we have the regular respiratory epithelium which is the still the stratified ciliated columnar epithelium but now in the oral pharynx and also in the laryngopharynx which is below the oral pharynx we have stratified squamous epithelium so several layers of squamous cells and if you pay attention to where the oral pharynx and the laryngopharynx are located you can see that these two parts of our pharynx are on the way of the food that we swallow so in this area we need several layers of cells so it's stratified squamous epithelium to ensure that the oral pharynx in the laryngopharynx can resist to our abrasion caused by the food we swallow now as I just mentioned the laryngopharynx is below the oral pharynx and the hyoid bone that we see here is what marks the line that separates the oil and the laryngopharynx so the laryngopharynx II starts at the level of the hyoid bone and it goes onto the entrance of the esophagus and as you can see the laryngopharynx is right behind the larynx that we see here now the larynx is our voice box and this is the place where we find our vocal cords three very noticeable pieces of cartilage make up our larynx the epiglottis the thyroid cartilage in the cricoid cartilage the thyroid cartilage is this big piece of cartilage that we see here and this is the place where we find the laryngeal prominence which is commonly known as Adam's apple right behind the laryngeal prominence we find our vocal cords in other words they were injured prominence is the place where our cords are anchored on tyranny as you know men have a more prominent bigger Adam's apple than women and due to testosterone the larynx of a man is bigger than the larynx of a woman and since we have the vocal cords in the larynx that results in the voice of a man being deeper than the voice of a woman now below the thyroid cartilage we find the cricoid cartilage and you can see here in the posterior view that the cricoid cartilage is the only cartilage of our larynx that has a posterior surface all other cartilages of our larynx do not have a posterior surface now between the thyroid in the cricoid cartilages we find the cricothyroid ligament and this ligament is clinically relevant because this is the place where tracheostomy is done because at this position you know you'd not damage the vocal chords of the person that's being unable to breathe so you make a little hole in the cricothyroid ligament and you allow the air to go into the person's lung in case the obstruction of the airway was located above this area here we can see the goddess which is this opening we have in our larynx and in the glottis we find the vocal chords that's why we say that the glottis is our vocal cords per se we have true vocal cords which are called vocal fold and we have false vocal cords which are named vestibular fold and as you can see the vestibular folds are located on the outside of the vocal folds they are called false vocal cords because they are not elastic enough to vibrate when air passes through them so they cannot produce sound so what happens is that when we breathe in the glottis opens up and air goes into our lungs now whenever we talk we are pushing air out of our respiratory tract and when they are passes through our glories it vibrates the highly elastic vocal folds and creates sound waves in fact if you put your hand on top of your voice box which is your larynx you can feel it vibrating and that vibration is what is producing the sound so as you can imagine depending on the tension length and diameter of the vocal folds different sounds can be produced and if we bring the vocal folds very close together we can produce very high pitch sound and if we put them apart we can produce very deep sounds and in order to tense or relax this vocal folds we must have muscles in this area and these are called intrinsic laryngeal muscles so the intrinsic laryngeal muscles regulate the tension in the vocal cords allowing us to produce the sounds or high pitch sounds and also this intrinsic laryngeal muscles they control the opening and closing of our glories so if we have intrinsic laryngeal muscles we also have exchange the Clarion jaw muscles because if we did not have both you just say laryngeal muscles right so the extrinsic laryngeal muscles they work extrinsically and they connect the larynx to the nearby structures and together if the movement of the hyoid bone when we swallow the extrinsic muscles in our larynx move up and down now you can ask me why do we have the false vocal cords if they seem to not do much right so the vestibular folds which are the false vocal cords they are mostly involved in helping to close the glottis so during the valsalva maneuver which is the name giving to the action of us forcing exhalation with our Airways closed we have the vestibular folds keeping the glottis closed and preventing the air from escaping and with that we have the increased pressure in the abdominal area and that helps during lifting of heavy weights and also during the vacation urination and during the delivery of a baby through the vaginal canal here we have an anterior view and a sagittal section of our larynx in one of the cartilage pieces that form our larynx is the epiglottis looking at the structure of our larynx we see that the hyoid bones to parts our larynx superiorly and connecting to the hyoid bone we have several swallowing muscles when we swallow these muscles pull the higher bone and consequently the higher it won't pose the larynx up and when that happens we have the epiglottis covering the godess and with that the food we're swallowing goes into our esophagus and not into our trachea so if you put your hand in your neck area and you swallow you can feel the larynx going up and when the larynx is up we have the epiglottis closing the entrance of our bodies now under the cricoid cartilage of the larynx we have the trachea and the trachea is this long tube that starts below the larynx and finishes with the split of the right and left bronchi all this cartilage that we see here the cartilage making up the thyroid and the cricoid cartilages of the larynx the cartilage making up the trachea and the cartilage making up the bronchi all this cartilage is highly in cartilage which is the type of cartilage that stuff but it is kind of flexible and that's why if we press our larynx we can feel it moving so the hyaline cartilage as all cartilages is a vascular but compared to the other types of cartilage the hyaline cartilage is the weakest type and we find the hyaline cartilage between the ribs and a sternum in articular cartilages we think synovial joints and in the passageways of our respiratory tract as you can see here now going back to the trachea the trachea is a tough flexible tube that held open by c-shaped hyaline cartilage rings and if you take a look at this cross-section of the trachea you can see that right there find the trachea we find the esophagus so when you feel the front of your neck that's the trachea and the esophagus is right behind it so the esophagus is posterior to the trachea lining the lumen of the trachea we find the regular respiratory epithelium which is the pseudo stratified ciliated columnar epithelium now look here at the ends of the c-shaped hyaline cartilage rings of our trachea you see that connecting the two ends we have a smooth muscle named Tracy Alice and as always most muscles throughout our body the trachea is muscle is under involuntary control and as you can suspect based on its location if the trachea is muscle contracts it decreases the lumen of the trachea because it brings the endings of the C shaped ring together and if the trachea is muscle relaxants the trachea dilates and the lumen of the trachea increases now you might be wondering why this hyaline cartilage is C shaped instead of a falling and the reason for that is because the esophagus is right behind the trachea and through the esophagus we have the food we swallow passing through now if the ring was a complete circle this swallowed food would go down our esophagus bumping into every single ring and these would cause no pleasant sensation it would be very unpleasant so the C shaped cartilage we have in our trachea allows the swallowed food to go down our esophagus a smoothly and in case we swallow something too big we have the trachea nice muscle getting a little pushed into the trachea lumen and with that the food keeps going down until it reaches our stomach now after the air passes through the larynx it flows down through the trachea and then it reaches this split point where we have the Carina of the trachea they can of the trachea is very important because we have several nerve endings grouping together at the Carina so in case the Brees are capable of getting into our trachea and get all the way down here reaching the Carina we have the free nerve endings at the Carina getting stimulated and we start coughing like crazy so the simulation of the nerve endings at the Carina leads to the coughing reflex and the coughing reflex is a defense mechanism because by coughing we can remove the breeze out of our Airways now when our trach is split we have the right and left main bronchi and if we compare this to main bronchi we can see that the right main bronchi is much wider and also kind of steeper than our left main bronchi so if you think that we have three lobes in the right lung and just two lobes in the left lung it makes sense that our right main bronchi is wider than our left main bronchi now taking into consideration that our right main bronchi is much wider and steeper than our left main bronchi if an object goes down our trachea would you expect the object end up in the right or left lungs the answer is right one right because the right main bronchi is wider and steeper than the left main bronchi so clinically what's found is that if someone aspirates a foreign object it is most likely to end up lodged in the right lung and interestingly the cigarette smoke is more likely to go into the right lung then in the left lung and so when we look at these mocking related lung cancers incidence the data reveals our higher incidence on the right lung then on the left lung but this higher incidence could also be related to the effect of us having one extra lobe in the right lung then in the left lung each main bronchi enters they made a spinal surface of our lungs through the heel and actually the hilum is the site of entrance and exit of always structures associated with or lungs including our blood vessels now after the main bronchi enters the lung it starts splitting too small and in smaller branches in this system of tubes that we see here that's formed by the main bronchi in their branches is called the bronchial tree and we can subdivide our learned lobes into bronchopulmonary segments in each bronchopulmonary segment is supplied by a tertiary bronchus now you don't need to worry about all these segments because I will not be testing you on that after the main bronchi enters the lung it subdivides into secondary bronchi that subdivides into tertiary bronchi and it keeps subdividing like 24 more times until we get to what we call bronchioles now this little bronchial is splits more until we get to out the other ducts and at the end of the oviduct we have the alveolar sacs also called alveoli as you can see there are some changes in the histology of the wall of this Airways as we get to smaller and smaller divisions so you can observe that with each subdivision as we go from larger to smaller in smaller Airways progressively have less and less hyaline cartilage so if you remember our trachea we had the hyaline cartilage in the wall and that was what prevented a trachea from collapsing but as we go into smaller and smaller a smaller Airways there is progress we realize hyaline cartilage in the walls and therefore these modern airways are capable of collapsing now another progressive change that is observed is that when we go into smaller and smaller Airways there is an increase in the amount of elastic connective tissue and also in the amount of his mouth muscle so the very small airways are very flexible and have a thick layer of viscera smooth muscle in the wall and this is muth muscle innervated by autonomic modern neurons that can cause the viscera smooth muscle to constrict so it narrows their way or to relax and in that case we have the airway dilating here we have a magnified view of the alveolar sac and we can see that reaching the viewer sac we have the alveolar duct in each lung has about a hundred and fifty million alveolar sacs and that's what confers our lungs they spongy texture it has all these ovular sects are surrounded by capillaries and as you know the capillary wall is formed by simple squamous epithelium which is the same tissue that forms the walls of these alveolar sacs so this area right here favors the gas exchange and in fact this is the only area where exchange can happen because the walls of both structures are thinking enough to allow gases to cross so we have oxygen that is inside the alveolar sacs getting out and going into the blood and the carbon dioxide that is inside the blood getting out and going into the alveolar sacs as you can see we have bands of elastic fibers surrounding the alveolar sacs and this elastic tissue helps in the maintenance of the shape and position of each of the other sac during inhale and exhale because as I mentioned before we do not have cartilage in this area because the presence of cartilage would not allow the gas exchange to happen now I just mentioned the walls of the ovular sacks are made of simple squamous epithelium so a single layer of squamous cells but these cells received the name of type 1 alveolar cells now it scattered among the type 1 of your cells we have another type of cell called type 2 all the other cells and the type 2 of the other cells are responsible for secreting surfactant if you recall the air that we inhale gets humidified and what happens is that when this humid air gets into this little sex and then we exhale we remove their out of these little sacks the humidity that was present in the air would make the walls of these little sacks to glue to each other leading to the collapsing of the alveolar sacs and consequently gas exchange cannot happen so this surfactant produced by the type 2 of Euler cells work as a detergent in the presence of this detergent does not allow the sides of the ovule or sacks to glue to each other because the detergent reduces surface tension and then you can keep breathing in and out we also find inside of the ovular sex macro fits in the function of these all the other macro fades is to engulf any virus bacteria or the bricks that are capable of getting into our lungs and with that the macrophage help us to not get sick now I'd like to share with you some diseases related to the respiratory system so here on the left side we have the alveolar sacs of a healthy person and on the right side the alveolar sacs of a person with emphysema emphysema is associated with the chronic progressive degeneration of the lungs and in a person with emphysema the alveolar sacs degenerate and this is chronic which means that it doesn't go away and it does not get better over time and by looking at this diagram you can see that emphysema not only affect their flow but it also affects blood flow and there is a dramatic impact on the ability of the oxygen to get the ovular sex and also for the blood to flow through the capillaries of the other sex to receive oxygen you probably have seen a person with emphysema and they are usually too weak to walk so they drive around in those little electric carts and they are usually carrying their air tank with them tobacco smoke is by far the most dangerous behavior that causes people to develop emphysema but emphysema is also associate with exposure to air pollution and chemical fumes and dust and a very small percentage some very rare cases we have emphysema caused by an inherited deficiency of the protein that protects the elastic structures of the lungs now most people with emphysema also have chronic bronchitis and bronchitis can be acute or chronic and the chronic bronchitis is the one that does not go away and it doesn't get better over time bronchitis is an inflammation of the lining of the bronchial tubes which are the tubes that carry air to and from our lungs so people who have bronchitis they often cough up thickened mucus and they try to eliminate the mucous from their Airways now asthma is a disorder characterized by the conducting Airways contracting too much and too easily so it is related to the tightening of the smooth muscles that surrounds our Airways in an asthmatic attack can happen spontaneously or after the exposure to a wide range of stimuli during an asthmatic attack there is inflammation in the air passage and that results in a temporary narrowing of the Airways that carry oxygen to the lungs and this leads to shortness of breath and chest tightening and if the America tech is very severe it even decreases the ability of the person to talk the last thing we need to talk about is the respiratory muscles and the important breathing muscles are the diaphragm which separates our abdominal and thoracic cavities and the intercostal muscles which are the muscles between our ribs and intercostal literally means between the ribs in order for us to inhale we have the respiratory muscles contracting now when these muscles contract they increase the chest volume and that creates a suction that draws air into our lungs as you know our lungs rest on top of your die Fryman and when the diaphragm muscle is relaxed it arcs up and it looks like this now the diaphragmatic enacted to the wall of our abdominal cavity so all the sides of our abdominal cavity because it separates the thoracic and abdominal cavities and when the diaphragm muscle contracts it gets shorter and as you know the shortest distance between two points is a straight line so when the diaphragm muscle contracts and it gets shorter it becomes a straight line and with that the chest gets bigger from top to bottom and when the intercostal muscles contract that enlarges the ribcage so it increases the chest from side to side and from front to back so the entire chest volume increases when these muscles contract and that lowers the pressure inside the chest and lungs and then we have they're getting sucked into our lungs and if you put your hands in front of your nose and you breathe in you can feel the air getting sucked into your respiratory tract and if you inhale very deeply you can literally see your ribcage expanding now when the diaphragm and the intercostal muscles relax the chest volume gets his mother and if the chest is smaller the pressure inside the chest increases so the air is forced out of our lungs so as a summary when the respiratory muscles contract we inhale and when the respiratory muscles relax we exhale and with these we finish this chapter please let me know if you have any questions bye