The Lymphatic System
The lymphatic system is not a very well-known system. However, it is a system of organs and vessels just as complex as the circulatory system, and just as essential to the survival of the human body, because it makes up the majority of our body's immune system. The lymphatic system consists of a network of vessels and nodes, along with a few specialized organs. It is also closely interlinked with the circulatory system.
Lymph and Lymph Vessels
Lymph vessels are specialized structures which transport the fluid they are named for-- lymph. Lymph contains white blood cells which are transported in and out of the bloodstream as necessary. If the body is invaded by a foreign substance, it is frequently transported from the bloodstream into the lymphatic system for disposal. The lymph vessels have no central pump, however, and so lymph must be transported by the peristalic contractions of the vessels tehmselves.
Lymph nodes are specialized structures which are found periodically along the lymph vessels. They are generally kidney-shaped, though less than one inch in length. Their function is primarily to remove foreign materials which are extracted from the lymph and deposited there. For this purpose, they contain large cells called macrophages, which engulf and destroy invaders. Lymph nodes also have a secondary function of storing lymphocytes, a type of white blood cell, and releasing them when necessary.
The lymphatic system contains several specialized organs to carry out its task of fighting didease within the body. Only a few are discussed below.
The spleen is a large, reddish organ (pictured here), located in the abdominal cavity. Though it is considered to be a part of the lymphatic system, it filters blood, not lymph. It searches for old, degenerating red blood cells, and breaks them down into their component chemicals for use elsewhere in the body. It also manufactures and releases lymphocytes, which have been previously mentioned.
The tonsils are patches of lymphatic tissue located at the back of the throat. They function to trap and dispose of the harmful materials which enter the throat through breathing, eating, and drinking.
Peyer's patches are similar in structure and function to the tonsils. Located in the small intestine, they serve to destroy the abundant bacteria which would otherwise thrive in the moist environment of the intestine.
written by Lyle Mullican