Visibly Human Health and Disease in the Human Body

The Lymphatic System

The lymphatic system has two principal components. The first is a network of lymphatic vessels that drains excess fluid, called lymph, from the body’s tissues and returns it to the bloodstream. The second component consists of organs of the lymphatic system. They are the tonsils, lymph nodes, spleen and thymus. These play an important role in defending the body against infection.

Lymph originates as excess fluid that escapes from the capillaries of the cardiovascular system and collects in the body’s tissues. It contains cellular waste, proteins, water, electrolytes like potassium and sodium and fats like cholesterol. Most of the lymph returns to the bloodstream directly through the capillary activity, while the remainder returns to the bloodstream through the vessels of the lymphatic system.

Lymphatic vessels often follow the same paths through the body as arteries and veins. The lymphatic vessels begin blindly in the body’s tissues. The smaller vessels merge to form progressively larger ones, until eventually they drain into one of the two largest lymphatic vessels: the right lymphatic duct and the thoracic duct. These two vessels return about two liters of fluid from the body’s tissues to the bloodstream every day. Unlike circulating blood of the cardiovascular system, lymph flows only once through its system of vessels.

The lymphatic system does not have a central pump like the heart in the cardiovascular system. Lymph in the lymphatic vessels circulates by contractions of the walls of larger vessels and also by the movement of the body’s muscles squeezing the vessels and forcing the fluid along. A system of one-way flap valves within the vessels ensures that lymph moves in only one direction.

Scrofula . Scrofula refers to tuberculosis of the skin. Tuberculosis is most commonly found in the lungs, but the organism responsible, mycobacterium tuberculosis, is capable of causing infections throughout the body. Infection with mycobacteria is usually caused by breathing in air that is contaminated by these organisms. The disease spreads to the skin from the underlying lymph nodes, bone or the lungs. Scrofula is manifested by the development of painful swelling that evolves into cold abscesses, ulcers, and draining sinus tracts. It is treated with anti-tuberculosis medications and sometimes surgery. This wax model showing scrofula was made by Jules Talrich in Paris, circa 1890. M-550 10070		Cancer of breast A large, cancerous tumor is visible on the left side of this breast. Breast carcinoma often spreads to other parts of the body through the lymphatic vessels in the axillary region (armpit). Nearby lymph nodes are commonly affected and may be surgically removed to prevent further spread of the disease. Breast cancer, the most common cancer in women, kills over 40,000 annually. As with other cancers, early detection can greatly increase the chance of full remission. 1990.0003.0972
Elephantiasis of the left leg . This is the leg of a 27-year-old man from Buffalo, New York. This patient had elephantiasis for 12 years; his leg was amputated in 1894. He recovered from the operation without complications. Doctors were unsure of how he contracted the disease because he had no history of visiting countries where the parasites that cause elephantiasis are common. Elephantiasis is the result of a combination of inflammation, scar tissue and overall enlargement of surrounding tissues in response to the parasite. It is still common in some tropical regions of the world today. AFIP 00499186		Elephantiasis of the scrotum The parasitic roundworm, Onchocerca volvulus, transmitted by black flies of the genus Simulium, can live in human skin, connective tissue and the lymphatic system. The worm can block the lymphatic vessels affecting the body’s normal ability to drain excess extracellular fluid from the tissues. Elephantiasis is the result of a combination of inflammation, scar tissue and overall enlargement of surrounding tissues in response to the parasite. The patient from which this specimen originated underwent surgery in 1968. He recovered without complication. At the time of the surgery the specimen weighed 40 pounds. AFIP 378622