welcome back welcome back welcome back to science all right now we're going to talk about the stomach we're going to talk about the cells involved and really the secretions and the enzymes that are going to be made we're going to talk about the different parts of the stomach and we're even going to get the point of talking about heartburn and vomiting all right so the stomach is going to be a j shaped organ as you can see it's shape here and the shape of this is named in different parts we're going to have the uppermost region which is going to be called the cardia and we're going to get into this area this is going to be called the fundus of the stomach As you move down you're going to have interior Linings these different folds these are going to be called ruching the bottom of the stomach is going to be called the fundus and this is going to be the body so the cardia fundus body pylorus these are the different parts of the stomach also we may notice the different kinds of muscles so notice that the muscles of the stomach are not all going in One Direction you're going to have this big long one going from an end it's going to be longitudinal you're going to have some that are going to be going around the stomach those are the circular muscles and you have some that are going to be underneath this going downward and that's going to be the oblique all of these three are going to be involved in helping the massaging of the stomach the contractions that's going to help ultimately in the production of the breakdown of food by and exposing more areas with surface area to volume and so the enzymes can break down the food so the stomach is going to see the food at the very upper portion here at the cardia and all right as this esophagus is going to empty into there's going to be a circular muscle called a sphincter this is going to be called the cardiac sphincter that's right there it's not labeled here it's this is called the lower esophageal sphincter it's anatomical name is the cardiac sphincture on the other end there's the pyloric sphincter but it's going to receive that food into the stomach once it gets into the stomach you're going to have gastric juices that are going to start breaking it down so this gastric juices are going to start the breakdown of different things like we have some fats that are going to be broken down here we're going to have proteins that are going to be broken down here but our chief thing that we're looking at is the breakdown of protein so when the food has been broken down to it's like next stage think of an assembly line that this is kind of the heart of assembly line where we're going to be going through a lot of different things getting it ready for the next phase but when it exits this area it's now ready for that next phase uh it has went through a lot of mechanical and chemical digestion so if you look at the the musculature of the stomach it's going to be made up of smooth muscle and we have circular muscles oblique muscles and oblique circular longitudinal no Bleak muscles interior we have the Rouge and the different structures as the stomach empties through the cardiac sphincter and to the cardia this is the fundus this uppermost part the funness is where you would find air because of just air rises so if you swallowed air or something like that that's where it would go here we have the body of the stomach and then we have the gastric folds as we're identifying this is lesser curvature greater curvature and we get to the pylorus there so those are the parts of the stomach so we're going to look at each part kind of what they do and then we're going to look at more of a microscopic side of things so the cardia is going to be the uppermost region and this is going to contain the lower esophageal sphincter which we identified as the cardiac sphincter the funness is going to be that rounded part that's going to be up towards the top an area called the cardiac now if you look at where the the cardia this is really close in proximity to the heart so the cardia its name is kind of a convenience in US remembering where it is so the fundus for the most part the food may go here but it's temporary gravity is going to pull it down this way and a lot of the liquids of the stomach are going to be here once again a little bit of air maybe here and so this is temporary storage if any all right the body this is going to lie below the fundus and above the pylorus so this is the body of the stomach and the pylorus this is going to be the distal portion closest to the small intestine and so you're going to get the pylor Seer the pyloric sphincter is there so the pylorus has the canal that's going to be leading towards the pyloric sphincter and that's going to be called pyloric canal and this is going to be the pyloric antrum so this area there all right so gastric secretions the gastric secretions are going to be tied directly to this area so let's take a look at this first we have parietal cells we have Chief cells this is the enteroendocrine cells that are going to be lowered down and we're going to see a few different things that are going to be here one is the chief cells which you can see those vesicles that are within this is going to make pepsinogen pepsinogen is going to be converted to pepsin which is a digestive enzyme but that digestive enzyme requires hydrochloric acid we know that there's acid in our stomach and so that acid has to come from somewhere and that's going to come from parietal cells so parietal cells have a mechanism where they're going to make an acidic condition and that acidic condition is going to convert the pepsinogen into pepsin so we need pepsin to break down those proteins so it's a nice complement system we're also going to look at some columnar cells that are also involved that are going to be making the mucus and the mucous neck so this area that we're looking at here this is deep down in these folds once again the folds create a lot of different increased amount of surface area as we look at the Rouge of the stomach so as you go down into this area you have the gastric gland that's going to be here and these the mucous neck this mucous neck is going to produce an alkaline type solution to protect the stomach lining so let's take a look at these different things from a different standpoint of the audible standpoint so pepsinogen inactive form of pepsin this is pre-useful and it is secreted by Chief cells pepsin is going to be when activated by hydrochloric acid it's going to break proteins down into polypeptides once again a polypeptide is going to be less than 100 amino acid a protein is bigger than 100 amino acids and so we're chopping this big structure into smaller structures we're going to look at different kinds of proteases that that are going to be involved later in the digestive tract and the small intestine that's going to be involved in the breakdown of these polypeptides but this is breaking it to smaller pieces so it can actually be use useful all right gastric lipase is going to break down fats it's a flat fat splitting enzyme think of a typical triglyceride which will have a glycerol and Three fatty acids we're going to have the cleaving of those different fatty acid chains from this by using gastric lipase there's different lipases that we're going to see along the way that's going to break that up further into smaller components hydrochloric acid is made by the parietal cells and we saw those parietal cells here once again hydrochloric acid producing cells here is the pepsinogen producing cells of the chief cells mucus is a protective lining it lubricates and keeps the stomach from digesting the stomach all right some intrinsic factors not mentioned yet this is going to be useful in the absorption of B12 without this we don't get B12 and we lead to other kinds of long-term suffering and disease all right so after we look let's just overview where we were thruge gastric pits within and as we move down here goblet cells and the columnar epithelial we get down into this intro interendocrine we have the chief cells we have the parietal cells all of these doing different things the mucosal neck which is really releasing that mucosa to protect the overall stomach so gastric juice is going to be continually made now how often it's going to be Contin it's continuous nature is let me say this differently it's going to be continually made but the amount may change that's the best way to say it controlling the amount that's going to be neural and hormonal all right so the neural component we've talked about a few times sympathetic being the fight-or-flight side of things and we have the parasympathetic as being the rest and Digest under a parasympathetic innervation we're going to have an increased amount of gastric activity so what does this really mean it's going to really assist me this is going to stimulate gastric secretion and now let's look at the hormones that are going to be involved in gastric secretion so somatostatins are going to be one that one of the somatostatins are involved they're going to cause digestion really slow down they're going to do this by reducing the amount of hydrochloric acid that is made since we have low amounts of hydrochloric acid that's made then we're not going to cause pepsinogen that's going to be converted to pepsin if we don't have pepsin being made we can't break down proteins into polypeptides gastrin its name is kind of Handy it's going to increase the amount of gastric secretions so this is under direct parasympathetic control which is really going to help the digestion in general all right cck this is going to be released in the small intestine this is going to be a type of feedback that we're going to see but it's going to help end the breakdown of protein and fat as it enters and it's going to decrease gastric motility so it's moving around it's going to be under that control so as impulse is from the parasympathetic preganglionic nerve fighter or the vagus nerve nerve 10 of the um the brain stem you're going to see it come off and it's going to have its response here parasympathetic postganglionic impulses stimulate the release of gastric juices from the gastric glands after that gas impulses stimulate the release of gastrin in the bloodstream that's going to cause the gastrin stimulates the release of more gastric juices so we're going to see positive feedback here and this is going to cause more and more of breakdown when we look at the phases of gastric secretion we have the cephalic gastric and intestinal phases cephalic is going to refer to head any time you were to see the word cephalo that's referring to the head so this is going to involve the parts of digestion where your body sees tastes smells uh the food oftentimes the enjoyment of eating food other than satiation is the cephalic phase where we're looking at something that just looks delicious or we taste something or smell something like Burger King is just notorious for having that Grill smell like oh that smells so good so that all helps start the process of gastric juices flowing causing your body to start its process you can think about your favorite food and you'll start salivating the reason you're salivating you're releasing salivary amylase and that amylase is used useful in breaking down starch so you're preparing for the breakdown of starch just by thinking about the food digestion the gastric phase this is going to have the actual release of gastrin where it's going to cause other gastric juices and reflexes to help in the secretion of gastric juices which is going to cause more and more of this digestion once it gets to this point I've went through and the creation of this climb it's then going to move into the intestinal phase where you're going to have the walls of the intestines that's going to be absorbing these nutrients as it's moving through so gastric absorption so now we're looking at the gastric phase so gastric has the enzyme Pepsis going to break down proteins the walls of the stomach that doesn't really do a lot of absorption it absorbs a little bit and this is what I can't absorb water certain salts certain lipid soluble drugs and alcohol this is why when people drink they're able to have an effect of the alcohol so effect so fast so the mixing of food with a stomach and gastric juices produces something that we're not calling the bolus anymore it's definitely not called food anymore this is going to be called chyme we looked at peristalsis remember that alternating contractions that move something down the small amount of time that is going to be transported through the pyloric sphincter by peristalsis we're going to have a little bit move through at a time and your body is going to use this peristaltic waves of the disproportion of the stomach to help push it back if it needs to and that's going to keep mixing it keep chemically breaking down the lower esophagus is going to prevent backflow of chyme into the esophagus this is what we call the cardiac sphincter so the emptying the raids depending on the amount of time and the type of food when all is said and done it's going to enter into the duodenum I hear some people call it the duodenum potato potato so the accessory glands are going to add secretions we will look at those that are going to act on the chyme as that enters the small intestine so when chyme starts to fill the duodenum stretch receptors initiate the enterogasteric reflex this slows stomach emptying and intestinal filling and so you own you don't want to just have massive amounts moving to your duodenum because you have a massive amount in your stomach instead you want to slowly empty it into that so digestion can actually work through the quicker things are moving through your small intestine the less time that you have to digest it and so you want to slow that rate and so inner gastric response is going to say like okay wait let's Digest all right let's have some more and so it has that continual process so what is vomiting vomiting is going to be the emptying of the stomach we are familiar with that certain drugs certain toxins certain toxins on your body with your body swallows that you immediately vomit and um this is your body's response to different poisons and so whenever it sees that poison it's like we need to empty this content right now so we don't die and so your body once again is kind of dramatic and it's going to purge the content Purge content evolution is supported why it's doing this because those that were purging survived those that just didn't because their body didn't probably receiving side effects and maybe they were eliminated earlier or maybe that poison got them so our body is going to vomit because of motion sickness body motion changes and the emotion sickness is tied to the some of the circular canals the otoliths that are in the ear for your sense of balance so the vomiting Center is going to be tied to your medulla obligata just below your pawns just above your spinal cord so to actually vomit these things occur and so this may mess with your vomiting one is you take a deep breath ever notice you take a deep breath before you vomit it you're going to raise your soft palate because you don't want the stuff flowing out your nose think of how often you vomited out your nose um really doesn't happen your glottis the thing that's gonna protect your nasal cavity you're going to have the relaxation of your esophageal sphincter you're going to have contraction of the diaphragm this is going to be that sheet of muscle that's going to be underneath each rib that that diaphragm animated by the phrenic nerve and this is going to cause contraction of the abdominal walls and force food out the mouth really unpleasant I don't recommend it all right so a problem uh a common problem heartburn heartburn is occurring when you have some of the digestive content that chyme that's moving instead of down to the pyloric sphincter it's moving up through the cardiac sphincter the lower esophageal sphincter is another name for that so you can get something like a stomach ache now the the fundus of the stomach is setting um where if you look at where it's setting and then you start moving the esophagus the esophagus is going to run just behind the heart and so if you're having pain in this region it's going to kind of feel like pain in the chest angina as you're looking at um you're gonna you know heartburn it's going to be this burning feeling that's going to be right behind your heart and it may think that you're having a cardiac event when really it's not the event at all so there's an old adage maybe a Yogi Bear quote if you want to lose weight stop eating 20 minutes before you get full so it takes your body about 20 minutes to feel like it's full so if you eat slowly there's a better chance that you'll feel satiated sooner without having the overeating if you eat fast you can eat a large amounts of food and you would have been full way before you stopped eating but you kept eating and then you eventually are overly full so except excessive fullness leads to abdominal pain and gastric reflux so gastroesophageal reflux disease gerd you have the contents that are moving up and from the stomach up to your esophagus so the way that you're going to neutralize an acid as it's moving into your esophagus is by taking an antacid so that provides some relief there's several different kinds on the market everything from Tums to Prilosec so ways that you can prevent heartburn eat small meals eat slower after eating stay upright so digestion and as a good rule of thumb just with anything avoid caffeine avoid nicotine avoid alcohol so even though those things make you feel good on other ways um they are problematic for most of your body so avoid those all right guys we'll get into the small intestine next I look forward to seeing you then so