 then comes the small intestine. From the stomach when the action of the stomach is complete then food from stomach enters into the small intestine. There are two parts of the stomach which are again important to mention we go back to the diagram where esophagus enters the stomach and where stomach enters the intestine. There are two groups of muscles called sphincters and at these entrances these sphincters which are ring formed muscles are closed and opened at intervals as required. So, when food is semi digested its proteins are digested the digestion of stomach is complete then food have to enter in the small intestine but food enters by the sphincter and it enters not in full but in smaller parts that is the sphincter opens and the food some part of food a bolus enters inside the small intestine and then sphincter closes again then comes the small intestine. Small intestine itself is a very very long canal or the tube its major function is digestion and then absorption of the food. Small intestine consists of three main parts duodenum the first part gygenum the second part and ileum the third part duodenum is the first part of the intestine. In duodenum food enters from the stomach in duodenum different types of enzymes and secretions are entered inside the first part of duodenum that help in the digestion of food. The secretions of liver which are stored in the bile which are stored in the form of bile in the gall bladder they are released into the duodenum. The pancreatic juice is also released inside the duodenum and the bile helps in the digestion of lipids it causes the emulsification of lipids that is it somehow attaches to the lipids and make them available for the enzyme action they convert them into a form on which enzymes can attack and break them down further. The pancreatic juice have various enzymes called trypsin the pancreatic amylase and the lipase trypsin is for the further breaking round digestion of proteins. We know that protein digestion already have been started in stomach due to the action of pepsin here in the duodenum due to the action of the trypsin protein digestion further continues due to the pancreatic amylase digestion of carbohydrate also starts and due to the lipase enzyme as we know the lipids lipase lipase action is to break down the lipids into smaller parts. So, the digestion go towards completion then the intestinal this part of the intestine the duodenum also releases its own juices that is its own secretions we call them intestinal juice. Intestinal juices also have various enzymes which break down the carbohydrates fats lipids the starch further and convert them into more smaller parts more smaller ingredients capable of further action by the next part. So, duodenum is the part of intestine in which there is and there is a very active digestion of carbohydrates fats and proteins occur. Then comes the juginum juginum is the is about 2.4 meters in length it is very very long in the juginum digestion of the food continues. The remaining digestion which is because food already have been broken the lipids are broken down the carbohydrates are broken down the proteins are broken down into smaller pieces in juginum this process continues. So, juginum is also mainly for digestion say we can say that this part breaks down the already broken part into further smaller pieces. Then comes the third part ilium is the last 3.5 meters of the small intestine this part is mainly meant for absorption because the food is almost totally digested in the stomach by the action of oral cavity first the starches by mylase then in the stomach by action of pepsin the proteins then in duodenum by the action of pancreatic juice the intestinal juice and the bile proteins carbohydrate fats they are all digested they are broken down into smaller pieces in ilium they are absorbed due to this reason ilium have a very specific structure because the digestive tube the elementary canal is designed to absorb the maximum digestive material from the intestinal lumen this lumen of the ilium is highly folded look at a diagram to understand its structure. Look at this diagram we can see on the top left the small intestine a part of small intestine from ilium we can see on the right a small section a very small section which is indicated by a black box which is actually zoomed in that is enlarged in this enlarged part we can see that the inner membrane of this ilium is highly folded and these folds are further folded you can see that there is there is a layer of muscles then there is a layer of submucosa then there is a layer of mucosa and then comes the folds and these folds are further folded that is the folds of the membrane have their own folds we call these own folds as villi these folds are called villi and these villi you can see in the bottom right you can see the structure of a villus you can observe that it is an extension of the membrane in which blood vessels are running and in between the blood vessels there is a small tube a blunt a blind tube going up we we we can we call this blind tube just inside a lactil around the lactil there are there is an artery towards one side and on the in red color and on the other side in blue color there is a vein if we look at the epithelial cell from this villus as indicated by the small black box and enlarge it we can see that all the cells of the villi even have extensions of their membranes towards the lumen we call them microvilli it means that every cell of the epithelium in this case we actually call them endothelium because these are present towards the lumen each cell of the endothelium itself have an extended membrane they call them microvilli you can see three cells all of these their with their nuclei are visible and their microvilli are visible why all of these foldings are present because intestine ileum this part of intestine the ileum have to absorb the maximum digested material from the lumen of the intestine and they can do so by increase excessive increase in the surface area due to all of these foldings you can see that surface area of for digestion actually we can say the area which is in contact with the food passing digested food passing through the lumen is highly increased due to these foldings so that this part of ileum is very very efficient in absorbing the maximum digested food from which is passing from the lumen of the intestine so this folding in the form of folds of the wall of intestine and then the foldings of this wall in further smaller parts the villi and the foldings of the epithelial cells of the villi themselves in the form of microvilli increases the surface area to several hundred folds and result is very very efficient absorption we can see in this next diagram a more closer look on the villus which shows a lactial inside two vessels one is in red color is an artery and the other on the in the blue color is a vein because you know that this epithelial lining of the villus is single celled you can observe in the diagram that the epithelium of this villus is only one cell thick so the materials can easily the digested materials can easily pass through this single celled villus and absorbed by the capillaries which are very very close by these arteries and the capillaries which are very very close present in close vicinity with the epithelium broken carbohydrates and proteins are digested by this way by the arteries and the capillaries but the fats and glycerols these are absorbed by this inner part which is running in the center the lactial lactial absorbs the fats and the glycerol and you can see down there that lactial is going down into a third vessel and it is not going to the arteries and the veins actually lactial is going towards the lymphatic system lactial brings the fatty acids and glycerols in the lymphatic system of the body which actually stores these fats at various places inside the body according to the mostly the genetic setup of the person that in which area of the body these fats will be located and if the fats are required by the blood then the lymphatic system returns these fats to the blood but the proteins the broken the digested proteins and the carbohydrates they are absorbed by the capillaries from the villi and then these digested fats and these digested proteins and carbohydrates are moved towards the liver and in liver liver is a very important organ is this context because liver removes all those toxic materials the waste materials from these semi these digested food particles smaller particles and make it clear and then through the liver through the hepatic portal vein these nutrients are moved towards the heart and heart then distribute these nutrients digested nutrients through the blood towards the whole body parts so this is how the carbohydrates and proteins they move they are digested in the intestine they are absorbed by the helium and they are they move towards the blood circulatory system then they go towards the liver where they are cleared up their toxins and their larger particles they are removed by the liver and then they are moved towards the they are sent towards the heart which distribute them in throughout the body then comes the undigested part what happened to the undigested which is not digested