welcome back welcome back welcome back to science all right today in chapter 17 section four we're going to be looking at the pharynx and the esophagus so for start first off we need to identify what the pharynx is the pharynx and the esophagus are going to both be involved with a highly highly muscular area that's going to be involved in the process of swallowing so the pharynx is going to have the cavity posterior to the mouth and then it's going to extend from the nasal passage all the way to the esophagus so we can look at the three different parts of this we have the nasopharynx oropharynx and the laryngeal pharynx the nasopharynx is going to be posterior to the NATO's cavity air passage containing openings to the auditory tubes the oropharynx is going to be just posterior to the oral cavity and it's going to be involved in air and food passage the laryngeal pharynx is going to be posterior posterior to the larynx that's going to be involved in the passage way to the esophagus the esophagus itself is going to be about a 10 inch to be the organ which is about from here to here that's about 10 inches and it's going to have a tubular organ that's going to extend from the pharynx to the stomach here is a posterior aspect where you can see the back of the tongue the epiglottis the kind of orientation here's the back side of the mandible we have a superior constrictor muscle middle constrictor muscle and inferior constrictor muscles and we have circular muscles that are going to be involved in the esophagus so in the swallowing mechanism the first stage is the voluntary stage you deciding to swallow your food so when you swallow your food excuse me excuse me saliva is going to be mixed with chewed food this is now going to have a new name instead of being called food or mashed up food it's going to be called a bolus so it starts as the food reaches the oropharynx and stimulates the sensory receptors and it's going to trigger the swallowing process the swallowing process is going to involve you raising the soft palate that's in the back of your throat so the soft palate is going to be here it's going to elevate so you're going to send the soft palate up you're going to send your hyoid up you're going to send your fairings up and so you're going to have the movement of these areas upwards towards the navel towards the nasal cavity but by moving the soft palate up it blocks the nasal cavity from food going up into the nasal cavity that would be a potential problem the hyoid bone and larynx also is are going to elevate epiglottis closes off the top of the larynx to protect the trachea so the epiglottis is going to be this piece of tissue that we see right here this tissue is going to fold down when it folds down it's going to keep food in the esophagus opposed to falling into your trachea so notice that when we're starting to swallow we push our tongue up into the back and the roof of her mouth and this is going to have the constriction these muscles here those Superior muscles as it's moving down you're going to have the epiglottis that's going to fold over the opening of the trachea causing food to slide down your esophagus excuse me um it's going to go through peristaltic action as it moves down your esophagus so the soft palate and the uvula Rays to protect the nasal cavity from the food the hyoid bone and larynx Elevate the epiglottis closes off the top of the larynx to protect the trachea then longitudinal muscles of the pharynx contract to the inferior constrictor muscles relax and the esophagus opens peristaltic waves is going to continue to force food down into the esophagus the third stage is the peristalsis part where food is going to that bolus is going to be pushed through the esophagus all the way down to the bottom where the stomach is here we have those peristaltic waves so the the esophage itself is about 10 inches 25 centimeters it's going to penetrate the diaphragm and at this point we're going to call this area the esophageal hiatus this is going to contain different layers it's going to have mucous glands in the submucosa which is going to moisten and lubricate which is going to allow for the inner wall to have mucus on it so food can continue to move instead of saying launched so in the muscularis the superior is the upper third the middle is um the middle uh the the middle third I guess and the inferior is going to be the bottom third lower esophageal area is going to empty into a circular muscle that's there at the top of the stomach called the cardiac sphincter the cardiac sphincter is going to be that circular muscle that prevents gastric juices that are in the stomach from going up and starting to erode parts of the esophagus if you have so sometimes this happens with gastric reflux disease as people have lesions that develop as a result of this so here we have esophagus 10 inch tube here's the esophageal Hiatus and it's eventually going to empty into the stomach all right guys this takes care of the esophageal part and the pharynx part I look forward to seeing you soon as we're getting to the stomach