the lower respiratory tract begins at the larynx and the larynx is made up of a thyroid cartilage I'm going to draw this from the front it's actually suspended by the hyoid bone so here I have the hyoid bone kind of going back and here's that hyoid bone the hyoid bones freely suspended and hanging from it from this connective tissue is the laryngeal cartilages or the larynx the voice box and the first cartilage we see is the thyroid cartilage it's named after the thyroid gland which it resembles which is inferior it may be vice versa that the thyroid cartilage is named after or the thyroid gland is named after the thyroid cartilage but they both have this central band of tissue where we get this narrowing okay now this cartilage doesn't wrap all the way around to the posterior it stops a bit shy but the cartilage that's hanging down from it known as the cricoid cartilage does wrap all the way around to the posterior now the trachea lodges these are only half cartilage rings that only wrap partially to the posterior where is that cricoid cartilage goes all the way around the thyroid cartilage only partway and here's my tracheal cartilages down and down this is quite a difficult structure to draw because we actually are trying to see the structures within it and behind it now on top of these cricoid cartilages we have these a shaped cartilages and they're going to be deep I'm not drawing them deep I'm drawing them more forward but understand that these are actually deep behind and sitting on top of the cricoid cartilage really within the lumen of the larynx and protect it in front by the shield of cartilage the thyroid cartilage now on top of them there's something called the ridiculous cartilages the car niculae cartilages well at the very base of these are it annoyed cartilages are going to be two ligaments they come anterior called the vocal ligaments and these ligaments are going to vibrate back within that voice box of the larynx and we control them by rotating these are written oide cartilages thanks to some muscles on the posterior aspect we didn't have to learn these muscles but I'll teach them to you now we have a written Oh a written oi muscles we have a written Oh cricoid muscles it come down to that backside of that cry cricoid we have Phi Rho cricoid muscles kind of across the front here or also kind of wrapping around towards the back there pretty simple names we have Phi Rho thyroid cartilage hyoid muscles and it's all these muscles collective effort that can manipulate these vocal cords or vocal ligaments making them more taut by rotating those or it annoyed muscles or creating a smaller or greater expanse there's tremendous amount of control and manipulation around our voice box because the voice box is responsible for phonation or making sounds it's also the airway passage into the lower respiratory tract and it's the last place where we could stop a piece of food that happened to make its way past the epiglottis which is surrounded here deep and able to when the hyoid bone using the thyrohyoid muscle polls the opening or this lumen that would be the pathway down into the lower respiratory tract gets pulled up into that epiglottis sealing the opening from any food particles that should go down there we can pull this whole mechanism up into that epiglottis and block the opening but when we're aspiring we're going to keep it relaxed and air is going to be able to make its way down past those vocal cords and the Associated anatomy down the trachea and into the respective lungs now there's some fanciful anatomy that you may read about including vocal folds false vocal folds false chords true chords okay the true chords are the ligaments the vocal ligaments and their surrounding mucosa but up above them alongside the walls of the larynx are additional folds and those are known as a false vocal cords or false folds okay you can check out additional images from the side from the back to try to gain a little bit additional perspective on the larynx or the voice box which is required for phonation and as an airway a route into our lungs but eventually from that airway and the tracheal cartilages we're going to make our way down to something called the Carina and the Carina is this highly sensitive Ridge of cartilage at the division into the left main bronchus and the right main bronchus now what this highly sensitive cartilage does as we're making our way down the trachea is if an object hits the Karina through neurological control it's going to induce a coughing reflex they can propel foods back out of the airway though the vocal cords are the last place that we could actually stop the food the Karina plays an important role in the coffret flex now you never put patients who smoke on a drug that inhibits the cough reflex and the reason why is the ciliary escalator of the respiratory mucosa which begins after those vocal chords and persists throughout the rest of the airway the ciliary escalator or the cilia on this ciliated pseudostratified columnar epithelium is paralyzed because of agents in the cigarette and so the only way for this person to clear debris out of their airway is thanks to this coffee reflex from this highly innovative tissue called the Karina at the bifurcation of the bronchioles her sorry have the main bronchus the left and the right okay now above those ligaments we found a different type of mucosa we had a stratified squamous epithelium that resists friction that was the same that we saw in the oral cavity in the laryngeal pharynx or hypopharynx and the oral pharynx so we went from respiratory epithelium up in the nasal cavity and stratified squamous epithelium in the oral cavity in the oral pharynx and in the hypopharynx and in the larynx where we might experience some friction but below the larynx we've returned to that respiratory mucosa that we would see in the nasal cavity and this is important to understand especially for people like dental hygienists if you're cleaning someone's teeth and you see an irregular bit of tissue in that oral cavity or on the lungs that has a slightly different appearance than the rest of the tissue you may be looking at the growth of some ciliated pseudostratified columnar epithelium on a macroscopic level in the oral cavity it does not belong in the oral cavity likewise stratified squamous epithelium does not belong up in the nasal pharynx or the nasal cavity or down here in the airway what you're seen is your seen a metastatic cancer cancerous cells that have spread into that oral cavity and if you can catch it at this time the prognosis is very good to remove that little bit of tissue and that person having cancer-free experience if you wait for somebody else to figure that out for this patient to have symptoms associated with oral cancers the prognosis is much worse so it's important to know what kind of tissues would be expected where okay now the right main bronchus is a little bit wider you see here than the left main bronchus it's also more vertical than the horizontal left main bronchus so if you happen to be a planters peanut the makes its way into I guess this looks more like a snowman I tried to draw the planter pinna guy but if he makes his way into the airway the more likely place to find objects that are aspirated or inhaled is in the right main bronchus because it's wider and more vertical the left main bronchus is narrower and more horizontal so the objects more likely to fall down this way now no object larger than approximately 7 microns or micrometers should make its way past the mucosa of everything leading to those vocal ligaments 7 microns is usually the limit of the size particles we find down here in the lower respiratory tract or at least this later part of it a red blood cell is about seven-and-a-half microns what that means is we shouldn't find particles larger than cells down in here and that's thanks to those vocal cords and the respiratory mucosa that hopefully filtered out a lot of that okay so we're more likely to find an object that's been aspirated over on this right side and thus in the right lung now that we've made our way into the right main bronchus or the left main bronchus we can start talking about the lung tissue and over here we have a laugh loan that was fed by that left main bronchus and over here we have a right one which is a bit shorter because that big liver is beneath it and it's a bit wider because it's not dealing with the cardiac compression in the position of the heart slightly up here to the left the volume of the right lung is larger than the volume of the left one and there's some other obvious differences between the right lung and the left lung well the right lung has a larger volume overall the left lung is taller skinnier the right lung wire or fatter shorter because of that litter that's underneath it now they both have an apex or a top point the apex and they both have a base a base they also both have costal surfaces diaphragmatic surfaces which is essentially saying the base and media spinal surfaces that are here against the mediastinum so the surfaces include the costal surfaces against the rib front and back and the diaphragmatic surfaces here against the diaphragm mediastinal surfaces here facing the heart thus off against the other structures passing nearby an apex and a base the right lung is a little bit different because this primary bronchus is going to divide into lobar bronchi of which there are three because the right lung has three lobes whereas the left lung has two lobes this is the main bronchus or primary bronchus I'm going to put the one degree sign these are the lobar bronchi or the secondary I'll put the two with the degree sign for secondary bronchi now as soon as bronchi divide they get a new name and these will go into tertiary or segmental bronchi tertiary or segmental bronchi okay about twenty three orders of magnitude we get smaller and smaller as we work deeper into those lobes of the lung so these are segmental the tertiary these are low bar these are primary bronchi now the low bar bronchi demonstrate to us that the right lung has more loaves than the left lung now the left lung also has something called a lingula and the lingula is maybe a remnant of what was once a third lobe that no longer exists so the we grab a better pen the right lung has an upper lobe and a middle lobe and a lower lobe or inferior lobe superior middle and inferior lobe fed by a superior middle and inferior lobe our bronchi one two three and separated by a transverse and then longitudinal fissure now the left lung only has that longitudinal or oblique I call this an oblique fissure but it does have this little bit of tissue here that's kind of like a tongue licking the heart lingula that may have once been a third lobe kind of like the way that the right lung house so we just saw some important differences between the right and left lung the left has just an oblique fissure the right has a transverse and oblique or longitudinal fissure the right lung is larger wider bigger volume has a superior middle and inferior lobe it also has different impressions because of the objects like the ascending aorta and the aortic arch to touch it whereas the left lung is going to have slightly different impressions like the cardiac compression on it so when you're looking at lungs you're looking at all these differences but usually when you're looking at lungs you're looking at something pathological and in and out of me we want to confirm that what we think we're looking at is actually what we're looking at so the way to be sure you're looking at what you think you're looking at is to look at the hilum or where these blood vessels which include the pulmonary arteries yes they would be blue pulmonary arteries that flow into each lung and the pulmonary veins pulmonary arteries and the paired pulmonary veins the return to the heart and the bronchi where they enter into the lungs is called the hilum and if we turn this right lung and we look on the mediastinal surface we can follow something called Rawls our a-l-s and this stands for right anterior left superior right anterior left superior and what this refers to is the position of the pulmonary artery relative to the bronchus this refers to the pulmonary artery it's position relative to the bronchus relative to the bronchus or the bronchi let me show you what I mean relative okay if I see the pulmonary artery and I know that I'm looking at a pulmonary artery because it's thick it's Peyton it's open the pulmonary veins are lower pressure they're more characteristics of things they're gonna be around like so okay but I know I'm looking at an artery because of the thickness it's not color coded necessarily in the body so easily and I see that broken cartilage of the bronchus here when I look from this direction at the lung where I take this long and I turn it from here so I'm looking at it like this this pulmonary artery is anterior to that bone guess I'm looking at a right lung okay that means that coming from the heart I have that right pulmonary artery coming like this now left is going to be superior this side that pulmonary artery comes in like this and it would actually be coming in superior so it actually comes in more like this to that main bronchus okay so when I look at the left side here's my main bronchus going into that hilum and my pulmonary artery I'm going to see grabbing your own color here and I know that I'm looking at my bronchus because I'll see those bits of cartilage and we might see some veins collapse now thinner walled around they're returning blood back to the heart so you can remember this acronym but this is the nail in the coffin when you're identifying a right lung from the left lung you look for these criteria but remember this person might have had some surgeries that alter the way that it looks and now that we're doing lung transplants light kidneys and other organs someone may be asked to go recover or to get that organ and bring it down for surgery and you want to make sure that you're bringing the right thing or left thing depending on what's been requested okay so over here what we may see let me see if I can get this right is from the pulmonary trunk we're going to see if we cut at the hilum and the hilum we're going to see that right pulmonary artery in front or anterior to the main bronchus and on the left side we're going to actually see it at the hilum more superior so something along these lines from that pulmonary trunk now the veins will be returning back to that a Horta but it's the pulmonary artery relatives of bronchus that we're concerned about to decipher right and left okay I'm gonna finish the lower respiratory tract by getting deeper and deeper into these bronchi and talking about the changes in the structure of the cells that will encounter