once the food or Kim is exiting the stomach through the pyloric sphincter it's going to enter the next region that is the small intestine as you notice for this illustration that the small intestine is going to be very large tissue amount of tissue all folded up inside the abdominal region we're going to see that almost all of the digestion and absorption of the nutrients and the food we eat is going to occur in the small intestine the small intestine is D divided into three different regions and each region has unique properties now the first region is called the duodenum you're going to hear this referred to as the duodenum Prime primarily by the clinicians however anatomists tend to refer to this as the dadum the term Duo means two and den means 10 so the dadum is about 12 Ines long and so then term Duo is correct and then Den would be correct for 2 and 10 however you choose to pronounce it will be fine the middle region is the dunum and then the distal region of the small intestine is the ilium this ilum in humans is going to be the largest part or region of the small intestine now the intestines are going to require a large amount of surface area in order to function with all of this absorption of nutrients and one of the tricks that our body has when it has a lot of tissue that it needs to fit into a small space is it folds it and we saw this in the brain we have all that tissue folded in up into the skull so the small intestines are going to have multiple layers or levels of folding at first we see beyond the folded up tissue and organ all put into the abdominal region then we have the folded inner surface of the small intestine and these are the circular folds on each of these circular folds the surface of this lining actually has these projections that are called the Villi so villis would be singular and on each villis is where we see the simple colomer epithelial tissue that has the brush border me membrane or lining that is made of the microvilli so here we see each individual villis in the small intestine and then we zoom in we see each villis is covered with the brush border or the simple columnar epithelial tissue and then we zoom in on each of these cells and we can see all those microvilli that we learned about in chapter 3 and on our cell model in lab in 168 and these microvilli these finger like extensions make up the brush border that we saw in the histology slide in 168 now each villus is going to include capillaries and this is going to be the location where nutrients such as the amino acids and the saccharides are going to be absorbed so these these nutrients are going to then travel through a unique passageway that hepatic portal system where the nutrients in the blood will pass through the liver to be quote unquote filtered before returning to the circulation however notice I said amino acids and saccharides so that's leaving out the other Macro Molecule or macronutrient that we eat which is the lipids most of our lip tend to be very large and so the digestive system we'll learn is going to package them into these unique protein packages called kyom microns and these kyom microns are not going to pass into the capillaries they're large they're hydrophobic so the lymphatic Lacs that are present in each Villas are going to function to take these kyom microns they will pass through the lymph and then we learned that the lymphatic system is going to jump into the lefts of clavian vein or the rights of clavian vein you may see kyom microns show up on lab values this is telling you the amount of dietary fats that are present so we see that in between each villis is going to the surface is going to dip so we call this the uh intestinal Crypts and there's a variety of cells that are present all along this lining in the intestine your average run-of-the-mill intestinal cell is called an osy so entro tells you intestines site tells you cell these are the type of cell that's going to function with the digestion and absorption of our foods and our nutrients on the apical side facing the Lumen of the small intestine you see these different shapes are representing what we call the brush border enzymes they are enzymes that are embedded in the membrane of those micro Villi that are going to help you to further break down these micro macronutrients into their monomers so that they can be absorbed on the basil side we see that there are going to be exchange pumps and different type of Transporters that allow the nutrients to exit into the circulation another type of cell we find in these regions is going to be the goblet cells with the mucus releasing mucus into the Lumen panth cells are going to have immune function they release substances such as lyes into the Lumen we won't spend time with these then we have the enteroendocrine cells so entro tells you small intestine endocrine tells you that the secretions are going into the blood notice the vesicles are on the basil side these substances that are going to function as hormones in the digestive system are going to be released into the circulation let's look at this duodenum each section of the small intestine has unique organization and structures to assist it with its unique functions so think about the Kim that has exited the stomach from the pyloric region through the pyloric sphincter into the duodenum it is going to be a very acidic solution because of all the hydrochloric acid from the digestion occurring in the stomach well we're going to learn that the small intestine is a location where a significant amount of digestive enzymes from the pancreas are going to be released these enzymes are going to be vulnerable in an acidic environment because they are proteins and they will denature therefore we see the duodenum is going to take care of that problem right away by neutralizing the acidic kind so we see that one mechanism for doing that is the sub mucosa has these unique glands that were going to release the mucus that is alkaline in nature because it contains bicarbonate the fluid that is released into the intestine is called intestinal juice similar what we saw with the gastric and it's going to include several different substances it's going to have the digestive enzymes it's going to have buffering components this illustration shows the brush border so all the microvilli on a scanning electron microscope image I like to show this because it's hard for us to see this in lab right on the membranes of these microvilli are enzymes and we call these enzymes the brush border enzymes and these enzymes are going to help to break down the disaccharides tacar eyeses as well as small peptides dipeptides into their monomers so they can be absorbed into the entos site so here we see a picture of the saccharides being broken down so we've got the tri and disaccharides that are going to be broken down down by their specific enzymes so for instance sucrose is a glucose and fructose joined together a disaccharide the enzyme sucrase will break it into each monosaccharide so it can be absorbed into the cell and then we've got our other other disaccharides as well the protein component so we in the stomach we broke down the proteins into small peptides so what we find Happening Here in the small intestine is on the brush Bard or is an enzyme that's called ocin or eptas that's going to activate that TR cinogen that's part of the pancreatic digestive enzymes and if remember that TR cinogen is a precursor once it's activated into the Tron then the Tron is going to act to activate the other peptidases kind of in a Cascade form now we can begin to absorb our proteins the digestive system is going to be regulated not just by hormones but also with neural stimulus so we have parasympathetic control of digestive system that's going to allow us to digest our Foods whereas the sympathetic nervous system is going to be inhibitory towards gastric activity and most of us know that when we're nervous you know our stomach doesn't feel that great we get the dry mouth no saliva coming out there are other reflexes that we touched on earlier associated with the passage of food through the digestive system we have a reflex well actually two reflexes here that are associated with the distension of the stomach so gastro tells you stomach and anic tells you small intestine so when the stomach is full and distended it's going to act on the small intestine and increase its motility and secretions which makes sense because the stomach is full it's telling the small intestine get moving move that stuff through because more is coming down the pipeline and on that same note when the stomach is distended with a full meal it's going to communicate with the ilium and that iloo valve and say get moving pass this food into the large intestine because we've got more coming down the pipeline the hormonal control of our intestines and our digestion is going to involve quite a few hormones this is not a completely comprehensive list of the hormones that we are aware of that are functioning with our digestion you will learn more hormones as you are out practicing uh clinically because we we are learning so much more and it's relevant to eating habits and eating behaviors and regulating eating and uh weight control and obesity and and diabetes and which are such prevalent problems in the United States currently I really like this picture it's a summary of the what we are looking at in all the different hormones where we've got the stomach food coming into the stomach it's going going to release that cause the release of that gastrin remember gastrin is like stepping on the gas so we're going to increase our secretions and our motility the stomach the Kim is going to pass through the pyloric sphincter into the duodenum and here we're going to see a bunch of hormones being released gastric inhibitory protein which does have another name also but this is GP is easier it's going to it's going to put the brakes on the gastron it's also going to cause the release of insulin we see secretin and colicy ainin are going to be released and these hormones are going to act on the pancreas for release of buffers and digestive enzymes and they're also going to go back and function to cause the release of vile from the liver and gallbladder and also not listed here but they function to at least cck to act on the hypothalamus and stimulate that feeling of satiety so let's look at each of these hormones a little bit gastrin remember we talked about that you step on the gas it's go from G cells the gastrin from the duodenum and from the stomach are going to be similar but different so for the purpose of the class the gastron from the duodenum we're going to think of it as just this last little stepping on the gas to get the last of the kind out of the stomach into the DM before that pyloric sphincter closes just like if the elevator doors are closing and you're telling everybody to hurry up get in get in get in because the elevator door is closing then we have secretin is going to be released with the stimulus of the Kim present and the secreton is going to travel through the circulation but stimulate the pancreas to release some buffers so so release some substances with bicarbonate ion in it to help neutralize the kind so this buffering substances are going to be released into the duodenum secretin is also going to stimulate the production a bile and release a bile it's going to slow activity of the stomach this Gip gastric inhibitory peptide is going to be the opposite of gastron because it's going to slow the motility and secretion of the of the stomach it also causes the release of insulin this type of function is very important today as we look at all the glp1 medications treating obesity cytic kinan is going to be another hormone release from the dagum into the circulation upon stimulus from the time arriving into the dagum this is going to act on the pancreas and cause the release of Digest enzymes the chosy is also going to cause the gallbladder to contract and release the bile that is stored and then what good is it to have this bile being released from the gallbladder if we don't open up that spincter that's going to let the bile and also those enzymes enter into the duodenum here we see pointed out that CK travels to the hypothalamus and signals satiety meaning a sense of fullness to tell us to stop eating VIP baso active it does what it it says it's going to act on the blood vessels dilating them this is going to just help keep everything moving along better absorption in ocin and this is going to uh help with the mucus Recreation here's another view of a synopsis of all these hormones and activities occurring now when the food has finished being broken down with the nutrients absorbed it's ready to pass from the small intestine into the large intestine so the ilum is the distal portion of the small intestine and each region of the small intestine is going to absorb different nutrients to a different degree so we see a lot of fats Etc absorb through the ilium then B most of the bile is going to be reabsorbed here but the food will not exit the ilium into the large intestine until the valve is open and this is our ilocal valve this is what is going to regulate passage of the food substance from the small intestines into the large intestine we looked at this iloo valve in our Pig now the next video we'll pick up with the large intes