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| Credit: Adam |
The lymphatic system is a collection of lymph vessels
and glands. It has 3 main roles:
- Fluid balance: return tissue fluid to the blood
- Protection from infection: produce white blood cells lymphocytes
- Absorption of fats: transport digested fats from villi to blood stream
1. Lymph and Tissue Fluid
Tissue fluid is a fluid surrounding the cells of a
tissue. It is leaked plasma - Plasma from the blood capillaries move to the
tissue through gaps in the walls and become tissue fluid.
Tissue fluid play an important role in substance
exchange between blood and cells. It supplies cells with O2 and
nutrients and takes away waste products including CO2.
At the end of the capillary bed, the tissue fluid leaks
back into the blood, and becomes plasma again, but not all of it. A little of
it is absorbed by the lymphatic vessel and becomes lymph.
The lymphatic vessel takes the lymph to the blood
stream by secreting them in a vein near the heart, called subclavian vein. The
lymph in the lymphatic vessels are moved along by the squeeze of muscles
against the vessel, just like some veins.
The return of tissue fluid to the blood in
the form of lymph fluid prevents fluid built up in the tissue.
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| Credit: lubopitko-bg.com |
2. Production of lymphocytes
The lymphatic system is an important component of the immune
system, which fights infection. One group of white blood cells, the
lymphocytes, are made in lymph glands such
as the tonsils, adenoids and spleen. The
glands become more active during an infection because they are producing
and releasing large numbers of lymphocytes.
The lymphocytes can live and multiply in
the lymphatic system, where they attack and destroy foreign
organisms. Lymphoid tissue scattered throughout the body filters out
pathogens, other foreign matter and cellular debris in body fluids.
3. The absorption of fatty acids and glycerol from the small
intestine
Following the chemical and
mechanical breakdown of food in the digestive tract, most nutrients are
absorbed into the blood through intestinal capillaries. Many digested fats,
however, are too large to enter the blood capillaries and are instead absorbed
into lymphatic capillaries by intestinal lacteals. Fats are added to the blood when lymph joins
the bloodstream.
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| Each villus contains a lacteal - a blind ending lymph vessel. |
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