Health and medicine
Lipid and protein transport in the lymphatic system
Learn about a third function of the lymphatic system. See how it finds a sneaky way to get fats and proteins into your bloodstream. By Patrick van Nieuwenhuizen. . Created by Patrick van Nieuwenhuizen.
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- at2:08, what are chylomicrons?(11 votes)
- Chylomicrons are basically little droplets of fat. When the fat we eat reaches the first part of the small intestine, the duodenum, bile produced by the liver interacts with the fat, emulsifying it (breaking it down) into little droplets, chylomicrons.(37 votes)
- If Chylomicrons are so large that they are unable to enter the blood vessels directly, how do they exit the blood stream after they have been dumped there by the lymphatic system?(10 votes)
- Membrane proteins on cells take up fatty acids from the chylomicrons, which slowly depletes them until there's just a chylomicron remnant. Chylomicron remnants are taken up and recycled in the liver.(13 votes)
- So if glucose were suppose to joint the capillaries nearby the small intestine, then wouldn't that part of the body and the parts below (because some glucose molecules may join in a larger artery) be supported by glucose? How would the head and arms get glucose?(2 votes)
- the Liver... he is the man. After absortion, he receive, armazenate and redistributes glucose to all the body cells who needs(9 votes)
- how the proteins or hormones will get out of the blood vessels to affect a certain cell if there size is to big to diffuse through blood vessels?!(4 votes)
- if chylomicrons are to big to enter the blood vessels, how can they come out from the blood vessels where it is needed?
It enters the blood vessel system through the lymphatic vessels. But how do they come out of the blood vessels?(4 votes)
- Intriguing question! Indeed, intact chylomicrons are too large to diffuse out of blood vessels, therefore they never do. Instead, after they travel through the bloodstream and release their lipid contents, they are transported to the liver and decomposed into smaller constituent proteins. :)(1 vote)
- I know someone already asked how Chylomicrons exit the blood stream, but what about the large proteins and waste products? If they can't get into the capillary vessels the how do they get out once they are dumped there, so they can do their job in cells in the tissue or get into pressed into your kidneys in the capsules? Thanks!(2 votes)
- Waste products are filtered out in the kidneys in glomerular capsules. The glomerulus within the capsule is fenestrated, meaning it has very large slit pores between the epithelial cells.
Proteins can either be broken down into amino acids and absorbed by villi via active transport in digestion or via endocytosis and, then broken down into amino acids, such as when a protein accidentally makes it through a slit pore in glomerular filtration.(3 votes)
- Shouldn't less protein be able to fit in lymph capillaries than in blood capillaries? If nothing bigger than a red blood cell can fit in a lymph capillary, how can those proteins enter the lymphatic vessels?(2 votes)
- It is said, that there are no proteins in interstitial fluid. So, where do those proteins go into from cells before they enter lymph? Thanks for the answer :))(1 vote)
- There are proteins in the interstitial fluid. The extracellular environment is full of different proteins that escape the vasculature, leading to the need for a lymphatic system to drain the tissues. This is why, should a lymph vessel become clogged, an entire limb could become swollen. (e.g. - elephantiasis)(2 votes)
- When does beta-oxidation of lipids happen? Is the making of chylomicrons a beta-oxidation process?(1 vote)
- Beta-oxidation of fatty acids occurs in the mitochondrial matrix, and it is defined as the breakdown of fatty acids for energy use. The production of chylomicrons is a step in digestion/absorption, and they are formed in order to move the stored triglycerides through the lymphatic system and into the bloodstream. After the bloodstream, the chylomicrons are either moved to the liver (beta oxidation in hepatic mitochondrial matrix), or an extrahepatic tissue.(2 votes)
- how does the high pressure of the fluid inside the lymphatic vessel prevent the plasma
from getting out.(1 vote)
- If I'm understanding your question, it was mentioned in an earlier video that there are valves that prevent backward flow and push the plasma forward.
But if you're asking about the structure of the vessel preventing the plasma from leaking, remember the structure of a lymphatic vessel. It's composed of endothelial tissues structured with tight junctions to prevent leakage.(1 vote)
We've already talked about two purposes of the lymphatic system. The first was to bring the fluid that was squeezed out of the capillaries back into the blood, and the second was to help out the immune system. But there's one more. There's a third. And that's what we're going to talk about in this video. So let's look at a piece of the small intestine. Now, obviously the small intestine carries bits of food that your body wants to absorb and use for energy. So one of the most important elements of that food is little glucose molecules, which are absorbed and are used as the primary source of energy for the body. So actually, since it'll be helpful for us, let's at least make this two dimensional. So let's look at some cells here of the small intestine. So these are cells lining the small intestine. And the way that glucose is actually absorbed by your body is that it's pumped into these cells here, in the cells lining the intestine. And then it's pumped out of them. And then once it's here in this space, it's able to diffuse into capillaries which are nearby. So it'll diffuse into the capillaries, and once it's there can go and spread out over the whole body and feed various cells. But glucose is not the only thing which needs to be absorbed in your small intestine, and actually another compound is fat. So fatty acids which are floating around in your small intestine need to be absorbed as well. And the structure of these things, to remind you, looks something like this. You've got this carboxylic acid group attached to a long chain of carbons. Now, like glucose, these guys are taken up by these cells in the intestine. But when they're put out by those cells, they no longer look like this. By the time they're put out, they're packaged into these actually rather large spherical objects which have a weird name. It's chylomicron. So they're packaged into these spherical things called chylomicrons, and these chylomicrons are useful for holding a lot of these fats together. But they have a problem, which is that chylomicrons, as you might guess, are too big to diffuse into the capillaries. So they can't do that. But you don't want to have chylomicrons just accumulating here in your intestine. You want to spread them out to the body where they're needed, and so that's where our good friend the lymphatic system comes in. So we have these lymphatic vessels nearby that are much easier to enter than the capillaries, and the chylomicrons able to diffuse into these vessels and be transported through the lymphatic system and eventually emptied into the blood circulation so that they can spread throughout the body. Because this is such an important processes, these lymphatic vessels in your small intestine are given a special name. And that name is lacteal. So the lymphatic vessels in your small intestine are known as lacteals, and those are the ones that take up your fats in the form of chylomicrons. So here we have our third important function of the lymphatic system, which is to transport things which didn't originally come from the blood, to transport them into the blood. And we can sort of generalize it a little bit and say that maybe a little further away from the small intestine somewhere else you have some cells that are hanging out. And actually, there are some other things which your body might want to put into lymphatic circulation. So you may have some cells here or elsewhere in the body that are producing maybe some proteins like hormones or maybe some waste products. And in some cases those proteins might have trouble getting into the capillaries, and these waste products also might have trouble. But you want these things to get into the blood because, for example, for hormones, you want them to be able to travel throughout the body and have their effects on the tissues that they're supposed to effect. And for waste products, you want them to be able to get into the blood and eventually get to the liver where they might be broken down or to the kidney where they can be excreted. So in those cases, you have this secondary system of getting these things into blood circulation through the lymphatic vessels. So these are proteins and wastes. And the reason that we're talking about these at the same time as chylomicrons is because these are all things that don't actually come from the blood, but we want to put them in the blood. And we can't do it directly, so we put them into lymphatic circulation first. So, now that we've learned about the third purpose of the lymphatic system, it might be a good time to review all three purposes at once. So why don't you pause the video and see if you can remind yourself of all three. Otherwise, I'll go ahead and describe them here. So the first purpose of the lymphatic system-- let's draw another lymphatic vessel here. The first purpose was to collect all the fluid which was forced out of the capillaries by the high pressure that's present in the blood, to gather all that fluid and bring it back into blood circulation via the lymphatic vessels so that you don't have too much fluid accumulating here in the tissue. So that's the first purpose. This is just fluid with maybe some small plasma proteins, but not with any red blood cells or anything like that. The second purpose had to do mostly with infection. So if you have some bacteria infecting some tissue in your body, the lymphatic system basically offers a way to bring those bacteria to the attention of your immune system. And they do that by basically taking them up and bringing them to the nearest lymph node. So that's a lymph node, and that is where your B cells and T cells are hanging out. So that's the second purpose right there, the second purpose of your lymphatic system. And the third purpose, of course, is what we discussed today. It's transporting other things, such as chylomicrons or other proteins or wastes, transporting them into the blood when they have trouble simply getting into capillaries the normal way.