Bilirubin

well let's look at the physiology of Billy Rubin and there's various parts to this story in the top left of the abdomen we have the spleen in the top right of the abdomen we have the liver coming from the liver you probably know we have the bile duck the gallbladder and going down the bile ducks are going to join up with the pancreatic duct and together these ducts are going to go into the duodenum the first part of the small intestine so we have the hepatic ducts the common patic duct the cystic duct the gallbladder common bile duct and the pancreas actually is around here like this this would be the pancreas itself with a pancreatic duct running through to collect the digestive [Music] enzymes and this common bit at the end is the uh hepatopancreatic ampula and there's a sphincter the hepatopancreatic sphincter forly called the sphincter of Odie and the small intestine Carries On judum ilium and then eventually it becomes the large intestine so here we have a stretch of large intestine ending of course in the rectum and the anus and the other part we're going to need to do this tell this story is the uh the kidney well one kidney of two now you probably know that the red cells are produced in the red bone marrow now when they're in the red bone marrow they have a nucleus but when they're released into the circulatory system they have no nucleus they're famous for being cells without nuclei so this means that gradually they get worn out in the plasma membrane which has got to squeeze through small capillaries in the spleen and the brain and the kidneys you know some of these capillar are so small that the red cells have to deform to get through and the the plasma membranes get old and they uh they rupture over time and also when cells pass through the spleen there's specialized cells in the spleen called macro fages macro fases in the spleen macr fases of course derive from monocytes in the blood and these are fixed macro proag is in the spleen there's also some in the liver actually and there's also some in the red bone marrow and these macro fages form the monoc site maccrage system what used to be called the reticular endothelial system and what they do is they take worn out red cells and they take broken up fragments of red cells so there's a r cell that's broken in half look and what the macro ages will do is they will phagocytose them they'll ingest and digest and break them down to break down products now one thing that is released is uh globin and another thing that's released is heem and I think you can see that this is the constituents of hemoglobin so the proteins and the fats and the carbohydrates in the not in that that's the maccrage in the Red Cell the maccrage will break those down and digest those quite readily so that will release things like uh amino acids fatty acids and um things that are useful the breakdown products and the globin also is broken down quite readily into Amino acids useful you can use it as part of the protein metabolism but the heem um is more difficult to break down but the iron that was in the heem there is iron in heem that's reabsorbed quite effectively actually the body can reutilize the iron um eventually it will go back to the bone marrow and form the next generation of red blood cells so that's brilliant but what's left of the heem part when the iron is removed and after the macro fases are finished breaking down the older erthrocytes what's left is Billy rubben so that's the breakdown product of the heem and Billy Rubin is yellow it's nice yellow colored pigment so remember Billy Rubin is yellow now the Billy Rubin is not water soluble so to be transported in the blood it must combine with Albin and that will transport it to the liver so now we have Billy Rubin in the liver now the the liver can't go on accumulating Billy Rubin it's going to need to get rid of it so to get rid of it it needs to make it water soluble so it can be excreted in the bile but it's not water soluble so we have to make it water soluble so what the liver does is it combines it with glucoronic glucuronic acid combines it with glucuronic acid and this process is called conjugated conjugation so conjugation is the process of joining look like marriage is a con conjugation isn't it it's a joining so the Billy Rubin joins with the glucuronic acid and the key thing about that is it makes it water soluble so it can go into the bod duct now remember the Billy rubben was yellow that's true it is but bile of course is a green color if you work on surgical W you see plenty of bile or even you might have vomited yourself and uh once the stomach's empty you can get regurgitation of bile because this is just the duodenum here where the uh the pancreatic and the B ducts drain their products into so they can be regurg ation so the bile is green you can as you say you can see it in vomits very unpleasant the old fashioned name for that is Gall it's very bitter and not very pleasant vomiting at all but it's it's green and and when it's green it's it's called um Billy verin verdant is green what actually happens is it's oxidized in the B ducts so in Fairly reduced form the Billy ruin is yellow when it goes into the bile duct it's oxidized and that makes it Go Green now when fatty food arrives in the duodenum that's going to stimulate the gore bladder and then the bile is going to go down and into the small intestine into the durum and there it will emulsify fats so the fat comes in in Big Oil lumps and the bile breaks it down into millions of little globules like that milk is why because it's a fatty Emulsion and that's good because it means that the pancreatic lipase from the pancreas is able to get in between all those globules with a large surface area and it's the lipas that digests the fat so the bile is emulsifying the fat but the lipas digests it so this means of course now we've got Billy Rubin in the intestine or Billy verin it's that similar molecule because it's got there from the bodu and it's fascinating of course that it's a waste excretory product in a sense but this is a vital physiological function to emulsify fats to facilitate the digestion of fatty material now in the small intestine you have huge numbers of commensal Flora lots and lots of bacteria Untold billions of them apparently uh feces is a third dry weight bacteria so there's huge amounts of bacteria and the bacteria act on the Billy Rubin that is of course in the Lumen of the gut and this is now the Lumen of the colon and the bacteria convert it to urobilinogen urobilinogen so now we have urobilinogen in the Lumin of the large intestine especially interestingly urobilinogen is not colored it's a it's a colorless agent or chemical but when this stays in the intestine it is part oxidized and when it's oxidized it becomes stir coilin so the urobilinogen combines with the oxygen to form stoin and stoin is what gives the stools their dark brown color so it's the urobilinogen oxidine in the Lumin of the gut forming stir coin giving the stools their dark brown color and in situations where there's the bile is not getting into the small intestine therefore the Billy Rubin is not present therefore the bacteria can't break it down to eurobin gen then you're not going to get the stoin so the stools are very pale colored which of course is an important clinical observation so the euren some of it stays in the Lumin of the gut but some of it is reabsorbed back into the blood and again in the blood it will be oxidized and the urobilinogen in the blood will be converted to something called when it's oxidized urobilin eurobin so two Fates for for the EUR eurogen it can be converted into stob Bolin to color and partly deod deodorize the feces or it can be reabsorbed as eurobin and the eurobin is is yellow again so interesting um one breakdown product of it stays in the Lumen of the gut is is dark brown this would be dark brown here the stool but um if it's real absorbed into the blood the eurobin it becomes yellow again so even though the urobilinogen is not colored itself it's got the potential to become dark brown or the potential to become yellow if it goes back into the blood now the eurobin is taken out by the kidneys and it's Incorporated incorporated into urine and that's what gives urine its characteristic yellow color sometimes it's called urochrome it colors the urine now because this is happening at a fairly constant rate it means that the amount of eurobin going into the urine is fairly constant a fairly constant rate per day it's about it's about 4 milligrams a day so this is good for us as healthc Care Professionals because if the urine's dark colored then the patient got relatively less water so we want light straw colored urine indicating that the eurobin and all the other agents in urine are well diluted so red cells bow marrow circulation monoy maccrage system broken down globin and heem the iron is recovered the heem becomes Billy Rubin carried to the liver conjugated with glucuronic acid excreted through the bile ducts emulsifies fats Billy ruin acted on by the commensal bacteria becomes urobilinogen the urob urobilinogen that stays in the Lumin of the gut is uh become stoin coloring the feces the component that is reabsorbed becomes when it's oxidized Euro so that's when it's oxidized becomes eurobin and is excreted in the in the kidneys and of course uh this is very important physiology to understand when we want to look at jaundice in the in the next video but that's the basic physiology we need to know about the Billy Rubin Billy verin story

Channel: Dr. John Campbell

Views: 24,551

Keywords: bilirubin, biliverdin, urochrome, urobilinogen, sercobilin

Id: 8jbvtUBUfmU

Length: 14min 46sec (886 seconds)

Published: Sun May 01 2016