The Lymphatic Vascular System

Lymph, the fluid in the lymphatic vascular system, starts out as excess tissue fluid. More fluid is pushed out of the capillaries by the high pressure at their arterial ends than is drawn back in by osmotic pressure at the venous ends.

Lymph vessels start out as tiny, thin-walled, blind-ended lymph capillaries. They join together to form larger lymph vessels, many of which have valves. Eventually the lymph is dumped back into the bloodstream.

Lymph nodes are nodules of tissue along lymph vessels. They filter the lymph and contain antibody-producing cells.

The spleen is a large, tongue-shaped organ located near the stomach in the abdomen. It has lymphatic and blood storage & filtration functions.

The thymus is an important lymphatic organ in young animals. Located on either side of the trachea in the caudal cervical and cranial thoracic regions, the thymus is large and active in young animals, but shrinks up and disappears in older animals.

Other lymphatic tissues include the tonsils in the pharynx, gut associated lymphatic tissue in the intestines, and small lymph nodules scattered beneath many epithelial surfaces throughout the body.