Respiratorytwo

The thorax is divided into three compartments the right pleural space the left pleural space and in between the mediastinum the pleural spaces consist of the lungs the pleura themselves the airways the blood vessels, the nerves and also the lymphatic drainage the lungs lie within the pleural cavity some people imagine that the lungs sit inside the pleura much like this the lung tissue sits inside of a bag and we would say this is the pleural tissue and this is the pleural cavity that's incorrect in fact the pleura is a sack within the sack another issue is that within the sack that makes up the pleura we're going to require some serous fluid this is an aid for lubrication so we're going to shoot that in there's a bit of serous fluid in there and then we're going to seal it inside with sellotape what really happens is that the pleura invaginates inwards. My hand is going to sort of represent that you can see it making a sack this sac will exist at the hilum of the lungs where the bronchi and the blood supply goes in as well as the lymphatics so we're gonna surround them the lung tissue with this sack which is made of a sack so now we have our lung tissue and on the outside of the lung tissue out here we're going to have one layer which is going to represent the parietal pleura and that will be up against the rib cage if we look inside of this we're going to have the visceral pleura the visceral pleura will be applied directly to the lung tissue and between the parietal pleura and the visceral pleura we're going to have the pleural space. The inside of that of course is that serous fluid and so the lungs then will be able to inflate and deflate and you'll be able to get some motion and between the visceral and parietal pleura which is facilitated by that serous fluid one thing to remember is that the pleural space is in fact the potential space there's not air in the pleural cavity, it's full of fluid only in the case of damage to the pleura will we get air forming in there now we'll talk about the surface anatomy of the lungs the lungs are of course paired structures sitting in a pleural sack now the lungs are attached to the other mediastinal structures the heart which is gone here,but would be sitting in this cardiac notch and the trachea so those other structures that make up the mediastinum if we look the lung has a number of different surfaces. We have the apex of the lung here there's the apex of the right and the apex of the left the apex will extend superiorly to underneath the clavicle and sometimes even superior to the clavicle. this is an important issue because if you're trying to put in an arterial line, for example, the subclavian artery or in other structures in that region. You may puncture the lungs may puncture the lungs superior apex the superior portion of the apex will be punctured and it can be damaged the other structure that we want to point out is going to be this region here called the hylum the hylum consists of the bronchus coming in as well as the neurovascular structures so the arteries veins and nerves that is the hylum we're talking about here there's the left hylum and then on the right it's not so obvious because the structures have been dissected away If we look again on the anterior side we will see that this part is going to be against the rib cage so we're going to refer to this as the costal region on these fixed lungs, you can see that there's a slight lump here and then again here this impression is left from the rib cage. And you wouldn't normally see that in lungs, but they've been fixed in that position other things that we can look at are on the right side. There's the right lung has one, two, three lobes and if we look on the left side we'll see that we have only two lobes. Now to be more explicit the right side with its three lobes will have a superior a middle and an inferior lobe if we look on the left long, we'll see that we have a superior inferior lobe and then this little structure we refer to as the lingula the reason that it's smaller on the left is of course because the heart picks up some of the left side of the thorax the lungs are separated by a fissure so there is the oblique fissure running down on the right side and there's the oblique figure riding on the left side the only difference is that on the right side we have one additional fissure the horizontal fissure running horizontally of course In order to understand the anatomy of the lungs and the pleura we have to make ourselves familiar with the surface landmarks that we have in that region so when you look at the surface anatomy of the lungs on a model we can see a few things right away first of all we have the clavicle running along here. The clavicle is going to terminate down by the jugular or suprasternal notch the lung itself is going to terminate in the apex which is about here and there's a dome on the top of the long that we refer to as the cupula if we follow a line that goes right along the clavicle, we're going to have our midclavicular line. so if we look on the right hand side we'll see the midclavicular line and down to this level, here is the xyphoid if we look here this is the sixth rib the lungs are going to terminate at about the area of the sixth rib whereas the pleura will continue down to about the region of the eighth rib So that's an area where there's a good separation between the lungs and the pleura now if we can get our model to turn sideways and lift up his arm we can see here the midaxillary line so this is his axilla, or armpit and so there's the midaxillary line now if we follow that to the eighth rib which is right here, our sixth rib is up here that is the end of the lungs on that side and the pleura is going to continue down to the region of the tenth rib now if we look on a model a plastic model we can look here and see the same structures here is our suprasternal notch, or jugular notch, and there is our clavicle we can follow down the clavicle and our midclavicular line until we get to the sixth rib if we look there at the sixth rib we'll see that's where the lung is terminating now if we turn this sideways we can see our midaxillary line and there's our sixth,seventh, eighth rib so you can see the lungs are terminating along the midaxillary line at the point of the eighth rib as mentioned previously the trachea will bifurcate into a right and left mean bronchus they're going to enter the hylum at that point and then they're going to branch immediately into secondary or lobar bronchi each lobar bronchus could correspond to a specific lobe of the lung there's the right superior lobar bronchus the right middle lobar bronchus and the right inferior lobar bronchus on the left side we're going to have a less superior lobar bronchus and a left inferior lobar bronchus as the bronchi guide deeper into the lobes of the lung the secondary lobar bronchi divide into tertiary or segmental bronchi on the right hand side we're going to have one, two, three four, five, six, seven, eight, nine ten segmental or tertiary bronchi if you look on the left side on this specimen we have one, two, three, four, five, six, seven eight, nine tertiary bronchi there can be eight to ten tertiary bronchi on the left side the right side is always at least ten the most important thing to remember about the tertiary bronchi is that they provide the air for a specific bronchopulmonary segment so what we're saying is this tertiary bronchi provides all the ventilation for one specific brocnchopulmonary segment each bronchopulmonary segment has an independent blood supply and we can illustrate it on this model so if we take it and turn it around we'll see the pulmonary arteries emerging here and here each individual branch of this pulmonary artery will be feeding a particular bronchopulmonary segment another interesting aspect is that each bronchopulmonary segment will have an individual branch from the bronchial artery so the bronchial artery is actually going emerge here, from the thorax aorta and send down it's arterial supply along the bronchi itself or individual branches will enter each of those bronchopulmonary segments the upshot of all this is that each bronchopulmonary segment has an individual branch from a pulmonary artery and an individual branch of the bronchial artery so when we look at the lung we'll see that the lung itself is divided into lobes and each lobe is divided into bronchopulmonary segments these bronchopulmonary segments are divided by a very thin layer of connective tissue the significance of this is that each bronchopulmonary segment has its own branch of the bronchial artery its own branch of the pulmonary artery and it's own tertiary bronchus what that means is if you remove a bronchopulmonary segment perhaps because of infection or damage, or cancer then they're going to end up not affecting the other bronchopulmonary segments in summary then, the lungs will be very resilient exposed to surgery as we continue from the trachea down the respiratory tree we'll find that these tertiary bronchi will divide into segmental bronchi and then into subsegmental bronchi the final major division will give us bronchioles now what is happening when we get to the smaller divisions is that we're losing the cartilaginous covering in the trachea and the primary bronchus we have c-shaped rings of cartilage if we get into the area of the tertiary bronchi they have become rings of cartilage those rings of cartilage will slowly diminish untill there's no cartilage around the bronchioles, or at least not complete rings. if we switch then to a model of the end of the respiratory tract we can see that we've got here is a bronchial this represents the cartilage which for the most part is not complete around the exterior the ends of these bronchioles are what we call respiratory bronchioles because some respiration can occur however the vast majority of gas exchange will occur here in the alveoli we'll turn these around and you can see that it's made up of a number of very tiny arteries and veins they're going to be bringing in the deoxygenated blood and of course oxygenated blood will be leaving these are branches of the plmonary artery that are coming down here and this is the branch of the bronchial artery so the final aspect of respiration is going to occur here in the alveoli and that was the true purpose of the entire respiratory tree. And so having discussed the terminal branches of the alveoli We have now wrapped up our section on the pulmonary system