16 December 2015
Lymphatic And Immune System
The Lymphatic System
The lymphatic system is closely related to the cardiovascular system. It is composed of lymphatic vessels, lymphoid tissues and organs, and lymph. The lymphatic vessels are composed of capillaries, collecting vessels, and trunks (Klein, 2010). Lymphatic capillaries drain into the collecting ducts that drain into the trunks. The trunks drain into the subclavian veins. Lymphatic organs in the body include lymph nodes, thymus gland, the spleen, tonsils, lymphatic vessels, and Peyer' patches in the small intestines.
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Lymphatic trunks join to form two major ducts, the right lymphatic duct and the thoracic duct (Smith & Fitch, 1993). The right lymphatic duct is rather short and drains the upper quadrant of the body. It drains into the right subclavian vein right at the junction with the jugular vein as shown in figure one above. Conversely, the thoracic duct is larger and longer than the right lymphatic duct and drains the remaining three quadrants. It begins below the diaphragm and drains the left side of the neck, head, and thorax. The intestinal and lumbar trunks join and form the cysterna chili that drains into the left subclavian vein.
Like in veins, lymphatic vessels have a low fluid pressure. They have valves that ensure that the flow of lymph is in one direction (Smith & Fitch, 1993). The vessels contract rhythmically to facilitate the flow of the fluids. Movement of lymph along the lymphatic vessels is aided by the pulsation of arteries and body movements. The flow of blood within the subclavian veins draws lymph into the vein as it drains into the subclavian vein.
The lymphatic system serves a number of key functions. The cells of the body have spaces in between them called interstitial spaces where fluid from blood vessels accumulates. One of the primary functions of the lymphatic system is to return fluid from the interstitial spaces back to the circulatory system. About15% of the blood that leaks out of the blood vessels into the interstitial spaces returns into circulation through lymph capillaries. Also, about 25 to 50% of blood proteins that leave capillaries do not get back to circulation through the blood capillaries but through the lymph capillaries. Lymphatic vessels also take part in the absorption of fats and fat soluble vitamins in the small intestines in lymphatic vessels known as the lacteals.
The defense system/immunity of the body is a function of the lymphatic system. The lymphoid organs take part in the synthesis of while blood cells whose primary function is the defense of the body against disease.Lymphoid organs such as lymph nodes screen bogy fluid as they flow through the body and removes pathogens together with damaged cells.
Just like blood vessels, the anatomy of the lymphatic vessels has been designed to facilitate the function of the lymphatic vessels. Lymphatic vessels primarily serve to drain lymph. The drainage of lymph in lymphatic vessels is influenced by the permeability of the lymphatic vessels and pressures within the vessels. The permeability of lymphatic vessels allows for the transport of water, ions, cells like the red blood cells, and macromolecules such as proteins.
Hydrostatic and osmotic pressures play a role in the drainage of lymph. There are two kinds of hydrostatic pressures.
Plasma hydrostatic pressure and tissue hydrostatic pressure facilitate the movement of fluids from the vessels into interstitial...