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Course: Health and medicine > Unit 1
Lesson 12: Lymphatic system introductionLipid 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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- at, what are chylomicrons? 2:08(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)
Video transcript
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.