 welcome back to the NPTEL lecture series on animal physiology. So, we are in section 12. So, today we will be starting with the lecture 4 of section 12, where we will be we are in the gastrointestinal physiology. And we will be talking about intestine and pancreas, if possible we will do the liver. So, as of now we talked about we first of all let us have a brief recap, those remains. So, the initially I give you the whole outline of from mouth to anus how the food is passing through. So, initially in the mouth we chew the food using our teeth, then there are taste buds along the tongue. And it is out there the salivary gland plays its role, it secretes a series of enzymes which helps in softening the food. And then through peristaltic movement the food travels down to the stomach. In the stomach it is exposed to a extreme acetic environment. And in that acetic environment series of chemical reactions happen the protein gets denatured they got broken down. And then food is further crumble down into very smaller pieces, from there the bolus or the whole lump of food moves to the small intestine, it is in the small intestine where the maximum absorption takes place. So, while we did about the cross section of the stomach we saw how the brush border like structures were there. A very similar kind of a structures indeed exist in the intestine, but much more higher surface area and the cell types which involved in it are different. So, what we will do essentially the same way we did for stomach we will I will draw the whole anatomy. And from there we will talk about the cross sections and we will talk about the different cellular structures which helps in the absorption process. So, getting back the slides. So, we are into section 12. So, we are talking about now intestine. And another thing what I am going to talk about today will be the pancreas. So, if you people remember while we talked about endocrine system I told you that there are series of hormones which are secreted by the pancreas and we will discuss those in the digestive system or in the gastrointestinal physiology. So, I think now since we are doing the gastrointestinal physiology once I finish the intestine we will move on to the pancreas. So, these are the two stuff what we are going to deal today to start off with small intestine. The anatomy of small intestine if you look at it. So, the food from the stomach moves and then there is a series of structures like this. It is a long loop like structure which is kind of you know something like this. So, this is a huge loop structure and of course, then it leads to the large intestine which kind of you know is fairly bigger diameter which is surrounding it which is also called the cologne before the food is kind of you know excreted out through the anus. And here you have the cologne and this zone what you see this whole tubular structure this is almost 20 feet long or which is almost in terms of 6 meters and the diameter range from 4 centimeter to 2.5 centimeter. So, these are some of the logistics and this whole small intestine is divided into several parts. So, I redraw this it is something it looks like. So, you have the entry port from where it is entering closest to the stomach that is called deodenum. Then you have next port which is next part which is called jejunum then you have sorry just bear with me this is just made a mistake. So, redraw it then will make sense. So, from here the food is coming entering from the stomach and now it is travelling all along the small intestine out here. Now, it is moving on to the large intestine out here from here starts the cologne. So, the first part is called deodenum then you have the jejunum then you have helium and then you have heliosecal valve heliosecal valve. This is the overall anatomy if I have to say how the intestine is divided intestine is divided into 4 parts deodenum, jejunum, helium, heliosecal, sphincter or heliosecal valve from where the food moves on to the cologne. So, it is a huge tube and this whole tube if I had to kind of given analogy of the histology the whole tube has borders like this all over something like this hairy border all over and this border is essentially what is termed as the brush border and those projections like a structure what you see like this which are projecting out those projecting structure are called villi villi. So, if you look at this so essentially what is happening? So, suppose the food comes the food particles are moving like this all along the villi. So, you are enhancing the surface area many many many folds by creating that villi like structure and this is how the biology designs it is a structure. So, that in a very limited space you can maximize your output. So, coming back now what we will do after giving you this anatomical features I will move on to give you that an idea about the histological aspect of it. So, we will take a cross section of this and we will talk about the histological parameters. So, coming back to the slides now so this is how it looks like if you look at the cross section of one of this is how it looks like and what you will see essentially lot of and if I could draw it in three dimension with something like. So, you will see all over the place there are brushes just like your toothbrush you see just like a toothbrush you will see lot of these structures and these structures are called villi which is the brush border and this whole raises structure is called plica plica. So, what essentially is plica if I going by the definition the plica is basically the intestinal lining basically the technical definition of plica is intestinal lining beers series of transverse fold called plicae transverse fold called plicae. So, it is very similar to the structure what we have explain in stomach which is called rugi if you remember that that structure in the intestine I was showing you in one of the flights that that is that surface is called rugi it is this and in the case of intestine is called the structures are almost same, but it is just their functional they are functionally different from each other because at this stage the whole idea is to absorb as much nutrient as possible that is the major so automatically when you have to absorb. So, you can understand if you look at the picture so this whole thing will have lot of blood vessels all around it likewise these blood vessels are continuously absorbing what server nutrients which one is kind of you know going through the intestine. So, this is continuously getting absorbed from the blood vessels and it has to be transported for you know synthesis of different kind of molecules now coming back to the slides on to the next slide. So, now what I will do I will draw the detailed structure of I showed you the I showed you this now what I will do I will just take one cross section out here from here one section and in the next slide I will show you the how that looks like. So, this is the bottom most layer which is underneath also there is a layer which is called Saroza layer this black what I am this base layer is called Saroza on top of Saroza you have muscular is external and muscular is external is something like this this layer is called muscular is external next layer on top of that you have the lever layer called submucosa. So, here I am into the submucosa layer which is so how about we give different colors to them so that you can identify. So, now we are entering into the submucosa layer. So, submucosa layer has the blood vessel all over the place this is submucosa on top of submucosa you have something called a layer very thin layer which is called submucular is submucosa muscular is sorry muscular is mucosa and on top of this you have the villi like structure. So, this is the total cross section of it and underneath you have something called lymphoid nodules and you have out here the intestinal gland or the this is also called crypts of libercans intestinal gland this is also called crypts of libercans two names for that this space region and now what we will do and these are the individual villi. Now what we will do after giving you the outline of this structure of the cross section of the of the intestine what I will do I will give you the individual villi how the cross section of the individual villi looks like and where are the blood vessels how the blood vessels are pulling the nutrients from individual villi because these individual villi. So, what is essentially happening if you look at this. So, the food is let us represent food with yellow. So, the food particles are all over the place this is moving the food particles are travelling all along like this and at this zones all the absorption is taking place all the different kind of all the nutrients which has to be absorbed they are getting absorbed here likewise and once they are absorbed they are further transmitted through the blood vessels which are present there. So, now after this we move on to the next light where I will draw the structure of the individual villi and we will highlight all the different structural features into it. So, now let us look at the cellular structure. So, the overall structure is not second overall structure is clear to you people. So, this is what you see what I am drawing now is a limb vessels which runs parallel to the blood vessels you saw the limb vessel which I was drawing. So, these are limb vessel now this is all surrounded by the blood vessels. So, they they come parallel to them. So, those blood vessels are out here like this they are all surrounding them in continuation you have the the venules which are the veins which are in in blue they are running in parallel and that is it. So, the red ones. So, this these are the veins and here you have the arteries. Now, is the cellular layer which is use a different kind of color for that cellular layer could see could be just using a slightly lighter color out here. So, that I can. So, this is how the cellular layer is and on top of the green which you are seeing the lining that is where I started all the brush borders. Now, what I am drawing now is just like your toothbrush if you look at it this. So, this is how a brush border structure looks like. So, the cells what are the different terminologies for the different cells out here some of these cells which are at the top what you see these are called goblet cells. Then you have the epithelial lining. So, most of these are epithelial cells then you have this part of the limb vessels is called lactial vessel lactial lactial network this is the capillary network and this part is called lamina propria. But in this process you must have observed that I have not highlighted one thing yet that is the nerves because nerves because it is innervating it is innervated very thoroughly by the nerve vessel. So, where the nerves are present. So, now let me introduce the nerves they are all over this. So, these nerves are moving all along like this these are the nerves all the sympathetic parasympathetic what you see. So, these are the nerve endings. So, this is how complex individual villi are and there are thousands and thousands and thousands of villi all along the small intestine and the food particle just like this. So, this thing this food particle is moving like this out here on these surfaces these are the food particles. So, they are following this route moving like this moving like this each one of them. And in that process what is happening essentially is the all the material what has to be absorbed are getting absorbed here and they are being taken up by the blood vessels and they are being taken up by the blood vessels and used for energy production. So, this is how the complete profile of the intestine looks like and this is how my intestine is absorbing all the different kind of material along its surface. So, now let us get back to the slide and try to tell you some of the different intestinal secretions what are the different intestinal secretions which are taking place and. So, roughly 1.8 liters of watery intestinal juice enters intestinal human per day and much of this being used for you know breaking up the like you know sorry for promoting the movement of the food and all other things. And the intestinal movements includes there are 2 sets of movements which are involved in the intestinal movement. One is called gastro enteric reflex which is regulated by the nerves reflex and I have talked about the reflex circuits already to you and there is something called gastroelial reflex. So, these are the major intestinal movement which is taking place in the intestine. So, this is the overall understanding of intestine what I expect you people to get from here what I will do I will move on to the structure of the pancreas what I told you. So, again with the pancreas we will do the same thing we will talk about the first of all the position of the pancreas where exactly it is located and we will talk about the secretion made by the pancreas and the role played by pancreas in the process of digestion. Let us we get back to the slide talking about the pancreas this is the stomach from the stomach out here and here start duodenum this is stomach and here starts the duodenum or the part of the intestine small intestine. So, the pancreas lies so organ like this constitute the pancreas. So, the structure the way I have drawn it is fairly similar to that it is kind of if you take a pepper and you cut it. So, the top part it is almost like that it is kind of inside a groove. So, what the pancreas does it is going back to the slides ok. So, if you look at the pancreas so this is very well innervated by the blood vessels which are coming all over and mind it this is also have a lot of endocrine function it has to take care of. So, this is the body of the pancreas then you have the pancreatic arteries these are called pancreatic arteries and out here are the where to do the cross section are the exocrine cells in pancreas which are also called assinins and those assinins are something similar to let me draw the assinins in the next slide assinins are very interesting structures. So, these are structures like there are vessels all along likewise and within those vessels you have circular structure like this draw it and it will make more sense to you people like this. These are further these further have the cells which are arranged like this they have this duct which are attaching. So, all of them have something like this I have come to the labeling and everything. So, these are the ducts and these are the exocrine cells in pancreatic islets. So, out here there are some series of cells which are more like this they have their own vessel. So, these cells which are present. So, there are these are the ducts what I have already drawn and you have the connective tissues in between which all over the place these are the connective tissues you have the exo. So, these are the exocrine cells in the pancreatic assinin these are the exocrine cells in pancreatic assinin and you have the endocrine cells which are these ones which are the endocrine cells in pancreatic islets which are also called islets of Langer hand cells. So, these are the cells is one which I have drawn in YOLO or slightly MADISH YOLO are the ones which are called islets of Langer hands or pancreatic cells which are involved in the secretion of a whole series of different factors which help in the digestion. So, what all pancreas is secreting. So, one is so p stands for pancreatic alpha amylase alpha amylase or carbohydrates basically this is breaking down the carbohydrates then you have pancreatic lipase which is essentially breaking down the lipids then you have nucleases which is essentially breaking down the nucleic acid then you have proteolytic enzymes which is taking care of all the proteins and peptides breaking all the proteins and peptides. So, if you look at the pancreas I have I have given you at least 4 different enzymes which is taking care of the fats lipids carbohydrates proteins and the nucleic acid apart from it also it has the endocrine function. So, now what we will do will enlist or enumerate all the endocrine secretion which are made by the pancreas. So, that includes and this so these are all the proteolytic enzymes we have talked about. So, now we will talk about a few other enzymes before we continue that. So, one is trypsinogen, chymotrypsin, procarboxypeptidase, proelastase and these are the series of additional enzymes which are secreted among the major class of the one which will be breaking down all the different proteins. So, after this we are left with few other aspect which pancreas is going to secret which helps in the digestion of the food. So, let us just go through what all we have covered. So, we talked about the intestine and in the intestine we talked about the structure of the villi where the all the absorption is taking place. Then we talked about the anatomical location of the pancreas and we talked about the major secretion made by the pancreas and the histological structure of the pancreas. So, what we will do in our next class we will talk little bit more about the pancreas about its endocrine rolls and then we will move on to the liver and we will finish up the liver and then we will move on to the large intestine. Thanks a lot.