Circulatory System – The Lymphatic System (part 4 of 4)

The human body has a second circulatory system, a system of vessels that transport a fluid called LYMPH throughout the body.

The capillaries are responsible for most of the diffusion of materials into the surrounding tissue; the small size of the capillaries can cause the loss of plasma into the body.

The lymphatic system drains the fluids that weren’t reabsorbed from the blood capillaries.

The lymphatic system is a series of vessels located throughout the body that help collect the plasma fluid/tissue fluid or LYMPH (a protein-containing fluid) that has leaked out of the blood vessels into the surrounding tissue. The Lymphatic system brings this fluid back into the bloodstream.

Lymph differs from plasma in that it has 50% fewer proteins and it does not contain red blood cells.

The LYMPHATIC CAPILLARIES are located in the spaces between cells where the fluid accumulates.

The lymph capillaries are slightly larger and more permeable then the blood capillaries.

The lymph capillaries merge into larger lymph capillaries called LYMPHATICS, which resemble veins but have thinner walls and more valves.

Lymph fluids are propelled through the body by capillary pressure, muscle action, intestinal movements and respiratory movements. These movements squeeze the lymph vessels and push the fluid along.

Lymph moves in only one direction, TOWARD THE HEART.

In addition to returning fluids back to the bloodstream, the lymphatic system is also the way that fat enters the bloodstream from the small intestine. On the lining of the small intestine are hair-like extensions called VILLI that contain vessels called LACTEALS. The lacteals are part of the lymphatic system and they absorb fat from food.

EDEMA is the swelling of a body area (like the feet or legs) that results from inadequate draining of lymph from the body.

Edema may be caused by heart or kidney disorders, malnutrition or injury.

The lymphatic system contains many oval-shaped structures called LYMPH NODES or GLANDS that are made up of connective tissue that contain PHAGOCYTOTIC CELLS (cells that can ingest other particles).

Lymph nodes are filtering organs that clear the tissue fluids of bacteria and other foreign particles. They filter and process the lymph.

The lymph nodes return the waste they filter back to the blood, where they are carried to the lungs, kidneys and sweat glands that eliminate them from the body. These wastes are detoxified by the liver.

Lymph nodes act as a defense and are located in the head, face, neck, chest area, groin, pelvic and abdominal regions of the body.

Lymph nodes can become swollen when the body is fighting an infection (swollen glands in the neck are usually a sign of an illness).

The lymph nodes and other lymphoid tissue like the spleen, thymus and tonsils are sites where LYMPHOCYTES (white blood cells) are formed.