Lymphatics are small capillaries that collect and carry extracellular tissue fluid, referred to as lymph, throughout the lymphatic system before it ultimately joins the bloodstream. These vessels can be found in almost all organs and tissues of the body, with the exception of bone, the central nervous system, the muscular endomysium, and the superficial layers of the skin. The basic functions of the lymphatic system include supporting the immune system by destroying pathogens, removing excess fluid and waste from tissues, and the absorption of fat from food.
Lymph is a watery fluid that contains several types of molecules, including proteins, glucose, urea, salts, and white blood cells, which help to fight infection. This fluid actually starts out as the plasma in blood, which flows into capillary beds where it delivers necessary nutrients to the cells and removes waste products. The majority of this plasma once again enters the blood circulatory system; however, a small proportion of fluid is left behind in the tissues, whereupon it is then referred to as lymph, and will be collected by the lymphatics and circulated through the lymphatic system.
Basically, the lymphatic system is the body’s first defense against infectious organisms and diseases, and has an essential role in immune function. In addition to the lymphatics, this system is also composed of nodes, which are small organs that contain many leukocytes. Lymph will pass through these nodes before entering the bloodstream, whereupon toxins and infectious material will be filtered out and destroyed. These lymph nodes, along with the spleen, are the major areas of the body where white blood cells fight infection. Other important members of the lymphatic system include the bone marrow and the thymus, which help to produce white blood cells.
Several disorders are associated with lymphatic dysfunction. The most common is lymphedema, or lymphatic insufficiency, which occurs when the lymphatics fail to collect lymph from tissues, resulting in swelling, or edema. Symptoms of lymphedema vary, ranging from mild swelling to disfiguring fluid accumulations and life threatening infections resulting from bacterial contamination of the protein-rich fluid in the tissue space. Lymphoma is a general term for a diverse group of cancers originating in the lymphatic system, most often from the malignant transformation of a lymphocyte. Lymphatic insufficiency can also occur in the digestive system, and this impairment can result in malabsorption diseases with serious consequences, such as malnutrition, immune impairment, underdevelopment of affected children, and even death.