in this video we're going to talk about the spleen the anatomy and the physiology let's begin by looking at the anatomy so the spleen is below our diaphragm on the left side it's actually under our ribs specifically between ribs 9 and 11 the spleen isn't is a intra peritoneum organ not a retroperitoneal organ and it lies in the left upper quadrant under the diaphragm so the tail of the pancreas also tickles the spleen and here is our duodenum the left kidney is below the spleen now a tear supply of the spleen it comes off the celiac trunk which is of the descending aorta specifically the splenic branch of the celiac trunk which is a tortuous artery that supplies the spleen and part of the stomach the drainage of this spleen is from the splenic vein which also drains part of the pancreas and then joins into the inferior inferior mesenteric artery before joining with the superior mesenteric artery which then forms the portal vein and remember the portal vein is what goes into the liver the esophagus comes off the diaphragm at the level of t10 meaning at the level of the 10th vertebrae and then the esophagus joins to the stomach the stomach is not drawn here but the stomach then joins with a duodenum which is the first part of the small intestine we drew earlier and it's important to know that the stomach is in close proximity with the spleen so talking about the spleen now well where the vessels go in and out of the spleen is the hilum of the spleen the dimensions of the spleen the spleen is about five inches high which is about 12 to 13 centimeters the spleen is about 3 inches in width which is about 7 to 8 centimeters the thickness is about one inch which is about 2.5 centimeters the spleen weighs about 7 ounces which is about 200 grams but this is on the heavier side now from all these numbers we have odd numbers in inches and an ounce so we have thus we can just call the spleen the organ of odd numbers 1 3 5 7 & 9 1 3 5 being the dimensions of the spleen in inches 7 their weight in ounces and this plane over is under the ribs 9 to 11 now let's now cut a section of the spleen and look at the pathology the histology of the spleen so here the spleen is actually covered by capsule and has to bycula coming within the tissues and here is the splenic artery which is breathing bringing blood into the spleen and it branches off into smaller arterioles called central arterioles they then continue on to become end arteries or end capillaries so they don't join straight away to veins anyway surrounding the arteries within the spleen are lymphoid tissues lymphatic tissues called the peri arterial lymphatic sheath or the peri capillary lymphatic sheath now the peri arterial emphatic sheath they are a lymphoid organ they contain immune cells mainly T cells and macrophages surrounding the peri arterial lymphatic sheath is another lymphoid tissue called the marginal zone here in yellow so here in yellow is the marginal zone which is made up of predominantly macrophages now sort of within this lymphatic tissue are other lymphatic tissues or clusters called follicles here in green the follicles are essentially surrounded by the marginal zone and contain immune cells called b-cells the peri arteriolar lymphatic sheath the marginal zone and the follicles make up what is known as the white pulp of the spleen the white pulp displayed make up 25% of the splenic tissue and because they contain immune cells they are thus important in fighting infections such as from viruses they are important in mounting an immune response as well as producing antibodies and we know this is so because if we if we remove the spleen of a person the person would have lower amounts of antibodies in the blood and people without spleens are at an increased risk of infection now going back to the splenic artery now when there is an artery there has to be veins the splenic art arch artery as we know branches into the central arterial and then it becomes end arteries or end capillaries it doesn't actually connect straightaway to veins to form veins these end arteries they have no wall which allows the red blood cells and other cells to essentially flow into the surrounding tissue and essentially it is the surrounding tissue where it gets picked up the cells get picked up by a sinus system here in blue and the sinus systems are the venous sinus that we're talking about and they are all around the end arteries all around the end capillaries here in blue the venous sinus picks up these red blood cells and then transports them to the collecting veins and then the collecting veins will join up and drain it into the splenic vein before leaving the spleen itself between the end arteries and the venous sinus is an area of tissue called the cords or also known as the cords of Billroth and this is essentially where we have heaps of macrophages there are a lot of macrophages which are your eating cells phagocytes within the cords of Billroth the cords and the venous sinus make up what is known as the red pulp the red pop make up the majority of the spleen 75% the red pulp is important in destroying or filtering abnormal red blood cells just unhealthy red blood cells as well as old red blood cells we know this because if we see the blood of someone with no spleen there is an increased number of abnormal red blood cells in the circulation for example there are red blood cells with Howley jolly bodies which are remnants of the nuclear the nucleus essentially so remember the spleen has a white and it has a red pulp let us now look at the white pulp and learn about it in a bit more detail let us zoom into this area here here we have the central arterial branching and it will bring in the red blood cell and other things through the white pulp area surrounding the artery remember is a peri arterial lymphatic sheath which are predominantly made up of T cells and macrophages here we have a T cell surrounding the peri arterial lymphatic sheath is a marginal zone in yellow which are made up of macrophages the follicles here in green is another lymphatic tissue which is surrounded by the marginal zone it is also it also has a capillary engine entering it or entering the area the follicles are important and they contain b-cells naive b-cells that have not been activated again in the marginal zone you can find macrophages which are antigen presenting cells macrophages can be your typical normal macrophages or these special macrophages called metallo philic macrophages but we don't have to go into detail on that let's now look at an example of what what the white pulp of the spleen actually does so let's just say that coming from the peripheral tissues for example coming from the skin a dendritic cell will bring an antigen into the spleen the dendritic cell does this because the dendritic cell is an antigen presenting cell and it is responsible for activating the adaptive immune system it's important in activating T and B cells so the dendritic cell will bring the antigen and present it to the T cells in the peri arterial lymphatic sheath the presentation of the antigen to the T cells will activate the T cells when the T cells is activated it will then activate the B cells in the follicle the activated b-cell can then become what's known as a plasma cell either in the red pup or in the white pulp the plasma cells are cells which actually produce antibodies upon activation the B cells can produce a lot of antibodies against that antigen that was presented in the first place the antibodies can be IgG antibodies which are the main blood antibodies or it can be IgM antibodies which are your initial antibodies produced another story could be for white pulp function could be that a pathogen such as a virus can enter the spleen by itself the virus gets in contact with the knife B cells in the follicle the B cells can pick this up and then it will present it to the nearby T cell and through what what is known as co-stimulation the B and T cell the B and T cell activate each other so the activated b-cell can then become a plasma cell again and then produce antibodies against that specific virus another way for mounting an immune response is where the macrophages itself within the spleen picks up these pathogens such as viral antigens it then presents the antigen to the T cells and then the T cells will activate the B cells and the follicles the B the activated B cells can then become plasma cells and then the plasma cells can produce antibodies against that antigen so as you can see the white pulp it is very important in mounting an immune response and also producing antibodies against infections or against other things now let's talk about the red pop which make up 75% of the spleen tissue remember the red pop is responsible for destroying or filtering old abnormal red blood cells let's zoom into this area where the venous sinus and n arteries connect so coming from the central arterial you have the branches of the central arterial and you essentially have the terminal capillary or the end artery it brings red blood cells and many other cells into the red pulp area the red pulp is made up of an area called the cords which are filled with macrophages the macrophage is surrounding the cords is also surrounding the venous sinus itself I apologize for the graphics of the video it became bad but hopefully you guys can still make up the drawing and what I'm saying so the red pop of the spleen again is made up of the chords and the venous sinus as you can see here there are slits between endothelial cells of the venous sinus and these slits are important in filtering red blood cells when red blood cells move into the venous sinus they are drained into the collecting veins before draining into the splenic vein so for example here we have a red blood cells and they are moving into the cords and then they will try to enter the venous sinus through the slits old abnormal red blood cells are unable to pass through the slit effectively and thus are phagocytized by the surrounding macrophages this is because the red blood cell is too slow or just unable to get through the slit because they have an abnormal shape for example and so this is the mechanism by which the spleen filters or destroys red blood cells viruses as well as other pathogens can also be captured by the macrophages in the red pulp and then be presented to the cells of the white pulp also finally opsin eyes pathogens or Upson eyes red blood cells which are basically pathogens or red blood cells that are tagged marked by the body are able to get destroyed by macrophages in this area so as you can see by all the examples I've given the red pop of the spleen is important in clearing out old damaged red blood cells as well as pathogens the final important role of the spleen asides from being being a white pulp and being a red pulp is sequestration of platelets platelets are also known as thrombocytes and they are circulating factors which are important in coagulation and forming clots one third one third of platelets are actually sequestered or stay in the spleen and so the spleen is actually important in maintaining good levels of platelets in circulation I hope you enjoyed this video on spleen anatomy and physiology thank you for watching you