The lymph system is composed of lymphatics or lymph vessels and glands and is a system with many functions. Fluid that bathes the cells (interstitial fluid) is returned to the cardiovascular system, in part, by the lymph system. This fluid, called lymph, passes through lymph nodes where impurities and foreign microbes are removed. Other parts of the lymph system include lymph organs such as the spleen. These organs produce cells that protect the body from foreign compounds, and have other immune functions such as cleansing the body of cellular debris and removing old blood cells from circulation.
The main exchange of fluid from the cardiovascular system occurs at the capillary level. Arterioles carry blood to the capillary bed and the venules return blood from the capillaries. About ninety percent of the fluid that flows from the blood capillaries to the interstices around the cells is reabsorbed by the capillaries. The remaining ten percent of the interstitial fluid enters the lymph system by lymph capillaries and travels through lymphatics. These lymph capillaries have one-way valves that allow the fluid to enter the lymphatics and not return to the cells. Once the fluid enters the lymphatic system it is called lymph. The lymph travels through the lymphatics and some of these merge into a large vessel in the abdomen called the cisterna chyli. This vessel, in turn, takes lymph to the thoracic duct that returns the lymph to the cardiovascular system. Label the structures of the lymph system and color them in.
Answer Key: a. Thoracic duct, b. Spleen, c. Cisterna chili, d. Lymphatics, e. Lymph nodes, f. Venule, g. Arteriole, h. Lymph capillaries
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.