lecture 4 of chapter 24 is on the pharynx and esophagus pharynx uh has three parts it's made of skeletal muscle and lined by mucous membranes the parts are the nasopharynx the oropharynx and laryngopharynx the nasopharynx only functions in respiration the oropharynx and laryngeopharynx are part of both the digestive as well as respiratory systems deglutation is the term used for swallowing and it's facilitated by both saliva and mucus it starts from the bowls of food that lump of food that you've created by chewing is pushed into the oropharynx and then their sensory nerves send signals to the deglutation center in the brain stem letting it know that there's food there the soft palate roof of your mouth lifts up it closes off the opening to the nasopharynx and then the larynx is lifted so the epiglottis that little Trash Can Lid um or Leaf covers the opening to the respiratory system called the glottis the esophagus is a collapsible muscular tube that sits behind the trachea connects the pharynx to the stomach unlike the trachea that's held open all the time with those cartilage rings the c-rings the esophagus collapses when nothing's in it we looked at at the structure of the GI tract and we have in the esophagus the mucosa submucosa and muscularis just like everywhere else but the outer layer is the adventitia there is a structural difference between this and the serosal serosa that covers the the outside of the GI tract in the abdomen so the esophagus does no digestion at all it's just involved in transport it pierces the diaphragm remember the diaphragm is the boundary between the chest and the abdomen it pierces it at an area called the hiatus this is the site where people can have Hiatal or diaphragmatic hernias what happens in a hiatal or diaphragmat diaphragmatic hernia is that the stomach protrudes up through the hiatus and herniates out the which causes pain it can cause if this becomes too constricted it can the tissue can start to become necrotic and you can end up with peritonitis and other issues the histology of the esophagus is covered very thoroughly in the histology lecture but just as a reminder we have stratified squamous epithelium on the mucosal layer in the submucosal layer we're going to have mucous glands to help lubricate the bolus of food going through there muscularis here is going to be a bit different in the very top the very beginning of the esophagus it's skeletal muscle because this is where we're going to initiate swallowing in the middle it's mixed between skeletal and smooth and the lower portion is completely smooth the um from that point on until we get to the external anal sphincter it's all smooth muscle there are two sphincters here that are circular sphincters remember a circular muscle there's the upper and the lower esophageal sphincters so de beautician moves ebolus from the mouth to the stomach and there are three stages or phases to this there's voluntary there's pharyngeal and esophageal voluntary stage starts when you force the bolus of food into the oropharynx by moving your tongue then there are receptors in there that stimulate the glutation center in the medulla oblongata and the pharyngeal stage begins the food then moves from the pharynx to the esophagus esophageal stage starts when it enters the esophagus and during this stage peristalsis moves the bolus from the esophagus to the stomach so the muscles that are involved we have pharyngeal constrictors the palatopharyngeious and the Stylo pharyngitis muscles help to elevate the larynx and the palatal muscles raise the soft palate okay so this is the first phase here it's called the buccal phase and this is moving the food from the pharynx to the back of the throat back the oral cavity and then the involuntary stage of the next stage is the pharyngeal and it's going to move from the pharynx into the esophagus and here you can see the epiglottis covers up the glottis so this bolus of food can move down the esophagus this collapsed tube and then we have the esophageal phase in which it's going to move through the esophagus to the stomach using peristalsis throughout the GI tract we're going to be looking at peristalsis quite a bit and peristalsis is quite similar to what you see if you've ever seen a constrictor snake swallowing who swallowed a mouse or rat or something movement that you see on the outside of their body as the prey moves through their body that's peristalsis so it happens you have the circular fibers behind the bolus of food Contracting and then the longitudinal fibers in front are going to going to relax so you have contraction behind and relaxation in front so it slowly keeps pushing it so it's you can think of peristalsis as a coordinated set of constriction and relaxation of the skeletal of the smooth muscle now the travel time for food the bolus of food is about four to eight seconds it's only about one second for liquids and then lower esophageal sphincter is going to open up allow the bolus to enter the stomach and then close again here you can see the different layers of tissue and the esophagus remember we have mucosa submucosa muscularis and then the outer adventitia a lot of people suffer from GERD or gastroesophageal reflux disease if the lower sphincter it can happen if the lower sphincter fails to open and then people the esophagus because the bolus of food can't move into the stomach the esophagus um distends and it feels almost like you're having a heart attack if the lower esophageal sphincter fails to close then the stomach acid can go up into the esophagus and cause heartburn some people just have a very weak uh weak a soft lower esophageal sphincter that doesn't close properly and they suffer from a lot of them suffer from GERD so there's a lot of tips that you can use to alleviate some of the symptoms or prevent it from happening if this is an issue don't eat a large meal and then lie down things like smoking and alcohol make this thing to relax even more so it makes the situation worse and if you can avoid certain foods that can help as well coffee chocolate tomatoes fatty foods onions and mint tend to be associated with higher levels of stomach acid you can also take Tagamet or Pepcid AC before you eat or after you eat try to neutralize some of the stomach acid with something like Tums people who suffer from GERD can sometimes develop something called Barrett's esophagus so normally an abnormal esophagus lower esophageal sphincter is going to keep the acid in the stomach and it's only going to relax when a bolus of food is moving down but in people that have Barrett's esophagus people who have Gerd the there can be a hiatal hernia there can be um the relaxation of the lower esophageal sphincter too much stomach acid all these things and acid comes up from the stomach and Alters the lining of the esophagus to make it more like the lining of the stomach so here you can see if you've looked at the histology you can see this is a stratified squamous epithelium and that is normal for the esophagus that's what it normally looks like this is a cross section or a section of someone's esophagus and you can see in here this does not look like normal esophagus you see mucous cells you see things that look akin to gastric pits and these are formed as kind of a means to protect the esophagus from the effects of this acid coming up constantly um what happens in these cells change and it's due to its const exposure to acid and a lot of people it's asymptomatic they don't realize they have this condition called Barrett's esophagus the problem with Barrett's esophagus is you have an increased risk of esophageal cancer so if it's determined that you do have it it's important to have endoscopy done periodically to monitor those cells to keep biopsying the cells looking at the cells and making sure that they're not turning into pre-cancerous cells that there's no dysplasia esophageal varices are another issue that you can have in the esophagus these are just varicose veins and you can see here it does sort of look like varicose veins and you can see how as Narrows the esophagus as well as creates a situation where it's not nice and smooth in here anymore this often happens because of problems with the liver so when normal blood flow to the liver is obstructed because your scar tissue from cirrhosis or there's some fibrous growth fibrous growths there it can't the blood can't go through the way it used to so it's going to find another root and the root it takes is through these um veins that go to this that come from the esophagus and these aren't designed to carry such a large volume of blood veins very thin walled they can't withstand a lot of pressure and so they start to leak and bulge out uh they can actually rupture as well so this can be mild to life-threatening uh you generally are going to have difficult swap difficulty swallowing and that's obvious by just looking at this picture but if these if these would uh tear open and bleed you could suffer um anemia or you could um have serious internal bleeding so it could be life-threatening the treatments for esophageal varices include medications to decrease bleeding medication using elastic bands to tie off the veins and diverting blood throat flow through a shunt blood flow from the liver through a shunt or liver transplant goals for lecture four listen describe the three phases of swallowing Define the following terms declutation gerd hiatal hernia esophageal varices Barrett's esophagus and I forgot to put one there peristalsis and to describe the histology the mucosal layer of the esophagus