A
lacteal is a lymphatic capillary that absorbs dietary fats in the villi of the
small intestineIn vertebrates, the small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where the vast majority of digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large...
.
The combination of fat and lymph in the lacteals is milky in appearance and called
chyleChyle is a milky bodily fluid consisting of lymph and emulsified fats, or free fatty acids . It is formed in the small intestine during digestion of fatty foods, and taken up by lymph vessels specifically known as lacteals...
. Individual lacteals merge to form larger lymphatic vessels that transport the fats to the
thoracic ductIn human anatomy, the thoracic duct is an important part of the lymphatic system—it is the largest lymphatic vessel in the body...
which empties into the left
subclavian veinIn human anatomy, the subclavian veins are two large veins, one on either side of the body. Its diameter is approximately that of the small finger...
found under the collar bone.
At this point, the fats are in the bloodstream in the form of chylomicrons.
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A
lacteal is a lymphatic capillary that absorbs dietary fats in the villi of the
small intestineIn vertebrates, the small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where the vast majority of digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large...
.
The combination of fat and lymph in the lacteals is milky in appearance and called
chyleChyle is a milky bodily fluid consisting of lymph and emulsified fats, or free fatty acids . It is formed in the small intestine during digestion of fatty foods, and taken up by lymph vessels specifically known as lacteals...
. Individual lacteals merge to form larger lymphatic vessels that transport the fats to the
thoracic ductIn human anatomy, the thoracic duct is an important part of the lymphatic system—it is the largest lymphatic vessel in the body...
which empties into the left
subclavian veinIn human anatomy, the subclavian veins are two large veins, one on either side of the body. Its diameter is approximately that of the small finger...
found under the collar bone.
At this point, the fats are in the bloodstream in the form of chylomicrons. Once in the blood, chylomicrons are subject to delipidation by lipoprotein lipase. Eventually, enough lipid has been lost and additional apolipoproteins gained, that the resulting particle (now referred to as a chylomicron remnant) can be taken up by the liver. From the liver, the fat released from chylomicron remnants can be re-exported to the blood as the triglyceride component of very low density lipoprotein (VLDL). VLDL, also subject to delipidation by vascular lipoprotein lipase, delivers fats to tissues throughout the body and, in particular, the released fatty acids can be stored in adipose cells as triglycerides. As triglycerides are lost from VLDL the lipoprotein particle becomes smaller and denser (since protein is denser than lipid) and ultimately becomes low density lipoprotein (LDL). A lot has been written about LDL because it is thought to be atherogenic.
Note that in contrast to any other route of absorption from the small intestine, the lymphatic system avoids first pass metabolism.
External links
- "117. Digestive System: Alimentary Canal jejunum, central lacteals "