human anatomy and physiology here we are looking at the respiratory system which is covered in chapter 22 of your textbook on this next slide we're looking at the learning objectives for the respiratory system which really comes down to understanding the structures and functions of the respiratory system and from more physiological standpoint understanding uh some of the nuances around ventilation and profusion uh and how we can have gas exchange and the transfer of blood gases um within our uh cardiorespiratory system so here we are in episode one uh so this is very much an introductory uh lecture looking at the structure of the respiratory system so what you can see here is an overview slide uh showing you several of the structures of the respiratory system and they function primarily to provide oxygen to the body tissues for cellular respiration in addition the respiratory system is known to help eliminate waste products such as carbon dioxide and also uh thirdly to maintain acid base balance so here we're thinking about uh pH there are other uh portions of the respiratory system that are used uh for more nonvital type functions when we think about uh our different senses uh such as being able to sense odors um but also uh with speech production and uh also uh in facilitating straining such as during coughing episodes uh Andor during uh child birth now on the next slide uh you will see a a table that uh divides off the two main zones of the respiratory system so we have a conducting Zone and a respiratory zone and the conducting zone of the respiratory system will include the organs and structures that are not directly involved in gas exchange and so so um that is how we uh make that distinction between once again the conducting Zone uh which really helps to bring air for example into the lungs but does not participate once again uh directly in gas exchange the gas exchange occurs specifically in the respiratory zone when we're referring to gas exchange once again we're talking about being being able to bring oxygen into the body and also being able to eliminate carbon dioxide and when I spoke about the respiratory system ability to regulate uh acid base balance we're talking about being able to regulate blood pH and that's through the regulation of carbon dioxide so the ability to actually eliminate carbon dioxide from the body um and and uh that uh is going to help us once again uh in regulating acidbase balance so as mentioned um here are the defining structures of the conducting Zone versus the respiratory respiratory zone excuse me so once again the conducting zone are those structures listed on the left hand column uh from the nose all the way to the bronchials that are not directly involved in gas exchange the three structures involved in gas exchange include the respiratory bronchials the Alvar duck and the alvioli and you can see an enlarged image of the Alvi uh showing in the screen here um and uh the structure is quite unique uh in the human body um and that really reflects maximizing surface area such that you can promote gas exchange in those structures now on the next slide we're looking at the uh thoracic cage and you can see the major bones uh including the sternum the ribs and the clavicle and you can also see some of the major muscles uh that also contribute uh when we think about uh breathing and we'll go into a little bit more detail on uh which muscles play a role in breathing um on a subsequent slide but uh just to uh highlight if few of the muscles um if you look on the right hand side of your screen some of the major muscles include the external intercostals and the internal intercostals well it may not appear uh entirely important right now you can have a look at the orientation of the fibers and the relative positions of those intercostal muscles so first the external intercostal muscles you can see that the mus fibers run on um on an angle or in an oblique uh Direction uh and you can see that they are the most superficial layer of muscles that occur uh or exist between adjacent ribs the internal intercostals also run on an angle or in an oblique fashion but they are um distinctly opposite to that um or or antagonistic uh to the external intercostals that has an implication for when we think about which muscles help with uh inspiration or bringing air into lungs versus those that help with expiration or uh being able to eliminate or get rid of air uh from uh the lungs these are more secondary muscles um and I say that uh as the major uh muscle involved in uh in uh breathing is the diaphragm and that's not showing on the screen here but we will come to it at a later time notably uh when we look at the overall structure though of the thoracic cage uh there is uh some unique features and so firstly when we look at the ribs uh they have somewhat of an elliptical shape and a unique attachment uh in that uh there is an angle of their attachment to the spine and this allows the thorax uh to actually help with uh being able to bring air into the lungs notably the thorax becomes larger when the chest is raised and smaller when it is lowered so once again um this structure is going to play a major role when it comes to both inspiration and expiration or bringing air into the lungs and then being able to expire or get rid of that air as well now you can see um a an image looking at the gross anatomy of the lungs so now we're going into a little bit more detail specifically uh the lungs are a pyramid shaped uh they are paired organs and that you have a left uh side and a right side they are connected uh to the trachea by the uh right and left broni respectively and as I mentioned um one of the major breathing muscles is the diaphragm and so at the inferior border uh or surface of the lungs um the diaphragm uh is a muscle uh which uh runs across uh and separates uh the thoracic from the abdominal cavity it is a large a fan like muscle it's very broad um and it is the major uh muscle uh located at the base of the lungs and the thoracic cavity you may also see it described as Dome shaped uh the getting back to the lungs though for a minute the lungs are enclosed by plura which are attached uh to the mediastinum the plura are um essentially uh like membranes helping to divide uh the the um tissue um of the uh actual organ versus the the uh structures that surround it the right lung is shorter and wider than the left lung and the left lung occupies a smaller volume than the right lung and this uh also is owing to the surrounding structure so if we think about the position of the heart inside of the thoracic uh region the the there is a cardiac Notch uh which is essentially an indentation you can see highlighted on the left lung and that allows uh space for the heart itself when we're naming off um the lungs and that the relative position at at the uh more superior versus the inferior uh loaves we also refer to uh these structures as the Apex um being most superiorly and the base being most inferiorly notably uh the lungs as you are aware um border the ribs so the ribs uh really act to protect uh the lungs uh as they are as they do perform a vital function given that um they are responsible for performing gas exchange we will get into it in a subsequent lecture um but uh just to be aware that the lungs obviously have a blood supply uh in particular uh when we think about the pulmonary arteries and the pulmonary veins they're not showing on the screen here but the uh pulmonary arteries play a role in providing deoxygenated blood to the capillaries that form the respiratory membranes with the aluli and uh in contrast the pulmonary veins return newly oxygenated blood to the heart for further transport throughout the body these uh lungs once again while not shown on the screen are also inovated notably by both the parasympathetic and sympathetic nervous systems and this helps to coordinate bronchial dilation and bronchial constriction of the Airways when we're talking about bronchial dilation we're thinking about the dilation or the enlargement of the bronchial structures um for example if you wanted to bring more air into the lungs versus bronchial constriction uh which would uh decrease the diameter of those bronchial structures and uh and and restrict uh air air the restrict the Airways next uh we have here the parial and the visceral plur of the lungs uh so as I mentioned uh each lung is enclosed within a cavity that is surrounded by plura plura is essentially a cirrus membrane that surrounds the lungs and uh once again you have a right and a left plura which enclose the right and left lungs respectively you can see them highlighted on the screen here just to be clear the plura consists of two layers there is a visceral plura and that is the layer that is superficial to the lung so it it surrounds the actual organ hence it is known as the visceral plura in contrast the parietal plura is the out layer that connects to the thoracic wall the medius dyum and the uh diaphragm so that is the outer layer um that typically uh is near the the outer structures that surround a given organ versus once again the visceral plura is the layer that is is immediate uh and in close proximity uh to the organ itself in this case uh being superficial to the lungs what you also know notice is a plural cavity and uh there is a space uh that is between the visceral and parietal layers known as that plural cavity lastly I'll just highlight uh that between the the um plura uh so between the parietal and the visceral plur there is something known as a um a plural cavity or sorry um plural fluid in the cavity and that acts as a lubricant so it allows the lungs to Glide across the thoracic wall during breathing and it also um acts in the prevention of plural separation it holds the lungs outward uh and uh towards the thoros couple more slides are almost on this first episode but here are the respiratory centers of the brain uh the control of ventilation is quite complex and involves multiple regions in the brain that help to Signal the muscles that are used in pulmonary ventilation this allows for a rhythmic consistent ventilation rate uh and provides the body therefore with uh adequate oxy oxygen uh while also removing carbon dioxide notably there are two interconnected control centers in the brain stem uh which helps to facilitate and generate that basic Rhythm of the respiratory uh cycle with nerves that affect both inspiration and uh expiration uh the related muscles associated with that so uh for example uh with um inspiration we have our diaphragm our external intercostals um but we also have uh we also have um our internal intercostals as well and lastly this is more for your interest but this uh highlights if you go to your textbook and have a look at figure 22. 29 how exactly uh the respiratory system develops and um you are not required to uh memorize this particular slide but what you can see in the take- home message really is uh that the development of the low respiratory system uh begins as early as week four uh to week eight uh within um within uh development