Describe The General Functions Of The Lymphatic System

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16.1 Introduction 1 Describe the general functions of the lymphatic system.
The lymphatic system is a vast collection of cells and biochemical that travel in Lymphatic vessels, and the organs and glands that produce them. It is closely associated with the cardiovascular system. The lymphatic system performs three important functions: fluid balance, lipid absorption, and defense.

16.2 Lymphatic Pathways 2 Identify and describe the parts of the major lymphatic pathways.
• Lymphatic Capillaries: are microscopic, closed-ended tubes. They extend into the interstitial spaces, forming complex networks that parallel the networks of the blood capillaries.
• Lymphatic Vessels: similar to veins, composed of three layers o Endothelial lining o Middle layer of smooth muscle and elastic fibers o Outer layer of connective tissue.
The larger lymphatic vessels lead to specialized organs called Lymph nodes.
• Lymphatic trunk: drain lymph from the lymphatic vessels, are named for the region they serve: o Lumbar trunk drains lymph from the lower limbs, lower abdominal wall, and pelvic organs o Intestinal trunk: drains the abdominal viscera o Intercostal and bronchomediastinal trunk: drains lymph from the thorax o Subclavian trunk: drains the upper limb o Jugular trunk: drains portion of the head and neck o Collecting ducts: ducts into which lymphatic trunks drain; in the kidney, tubule that receives fluid from several nephrons
Thoracic duct—it begins in the abdomen. It passes upward medially through the diaphragm to the left subclavian, where it empties.
Right lymphatic duct—it begins as the union of the right jugular, right subclavian and right bronchomediastinal trunks. It empties into the right subclavian vein. o Subclavian vein: 16.3 Tissue Fluid and Lymph 3 Describe how tissue fluid and lymph form, and explain the function of lymph.
Filtration from the plasma normally exceeds reabsorption, leading to the net formation of tissue fluid. This increases the tissue fluid hydrostatic pressure, the force which moves tissue fluid into lymphatic capillaries, forming lymph. In this way, lymph formation prevents the accumulation of excess tissue fluid, or edema.

16.4 Lymph Movement 4 Explain how lymphatic circulation is maintained, and describe the consequence of lymphatic obstruction.
Hydrostatic pressure of tissue fluid drives lymph into lymphatic capillaries. Muscle activity largely influences the movement of lymph through the lymphatic vessels. Breathing also aids in movement of lymph. Interference of lymph circulation causes tissue fluid to accumulate in intestinal spaces producing edema.
16.5 Lymph Nodes 5 Describe a lymph node and its major functions.
Lymph nodes (lymph glands) are located along the lymphatic pathways. They contain many Lymphocytes and macrophages (histiocytes) that fight invading pathogens. 6 Identify the locations of the major chains of lymph nodes.
• Cervical region: lower border of the mandible, anterior to and posterior to the ears, and lie deep in the neck.
• Axillary region: wall of the thorax, mammary glands, and the upper wall of the abdomen.
• Supratrochlear region: superficially on the medial side of the elbow.
• Inguinal region: the external genitalia and lower abdominal wall.
• Pelvic cavity: pelvic viscera
• Abdominal cavity: main branches of the mesenteric arteries and the abdominal aorta.
• Thoracic cavity: in the mediastinum and along the trachea and bronchi.

16.6 Thymus and Spleen 7 Discuss the locations and functions of the thymus and spleen.
• Thymus: Is located in the mediastinum, anterior to the aortic arch and posterior to the upper part of the body of the sternum and extends from the root of the neck to pericardium. The thymus is subdivided into lobules. The lobules house many lymphocytes that develop from progenitor cells in the bone marrow. Most of these cells