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5.8. Lymph and lymphatic system

Lymph and lymphatic system

The cells do not take nutrients and oxygen directly from the blood vessels, but take it from the interstitial plasma, liquid from the blood that occupies the space between the cells. The excess of this interstitial fluid, and loaded with other waste substances, is collected by a drainage system, the lymphatic system, which will return it to the blood in the subclavian veins. This liquid is known by the name of lymph.

As you may remember from when it was said about the absorption of nutrients in the intestinal villi, it was said that the fats did not pass into the blood, but that the chyliferous vessels absorbed the fats to take them to the lymphatic system, and later they would reach the blood.

In the lymphatic system there is no organ that pumps the lymph, but it is moved by muscle contractions and movement of the limbs.

Lymph is a clear liquid with little protein and rich in lipids. Because it comes from blood, it is very similar to blood plasma, but the only cells it contains are white blood cells, which come from the lymph nodes. Lymph is less abundant than blood, since we have about 2 liters.

In the same way as in the circulatory, the lymphatic capillaries join into larger vessels, the lymphatic veins, but these flow into the  subclavian veins.

We can summarize the functions of the lymphatic system in:

  • It collects excess interstitial fluid and returns it to the blood.
  • The lymphocytes defend the body against infections.
  • The chyliferous vessels absorb the fats that the intestinal villi cannot absorb and carry them into the blood.

Answer in your notebook

5.22.- Where is the interstitial fluid found?