anim_lymph_formation_flow_answer_key.doc

Lymph Formation & Flow To complete this worksheet, select: Module: Distribution Activity: Animations Title: Lymph Formation & Flow Introduction 1. Define the lymphatic system. The lymphatic system is a network of vessels and tissues that contain and transport lymph. 2. Where does lymph come from? Lymph forms from interstitial fluid in the lymphatic capillaries and flows through lymph vessels and nodes, eventually returning to the blood vessels. Lymphatic System Functions 3. Name the three major functions of the lymphatic system. The lymphatic system drains excess interstitial fluid from tissues. It also transports dietary lipids and lipid-soluble vitamins A, D, K and E that are absorbed in the intestine. The lymphatic system also promotes disease resistance. 4. Each day about 20 liters of fluid filters out of blood capillaries at the arteriole end. About 17 liters of this fluid is reabsorbed at the venous end. What happens to the remaining 3 liters of interstitial fluid? The remaining 3 liters of interstitial fluid and solutes are drained and returned back to the blood by the lymphatic circulation. 5. Describe the function of lymphatic capillaries in the small intestine. In the small intestines, lymphatic capillaries known as lacteals absorb dietary lipids. 6. How does the lymphatic system promote disease resistance? Macrophage cells found in the lymph nodes and spleen phagocytize invading cells. The B-lymphocyte cells in the lymph nodes and spleen produce antibodies that target and destroy foreign antigens and cells. Formation of Lymph 7. a. How does lymphatic capillary structure define its function? The capillary wall’s unique structure permits fluid from the surrounding space to flow into the capillary but not out of it. Endothelial cells that make up the lymphatic capillary wall overlap and anchoring filaments tie the endothelial cells to the surrounding tissue. b. How does pressure determine lymph movement? Excess fluid accumulates in the tissues causing swelling. Anchored filaments pull the endothelial cells slightly apart allowing more fluid to flow into the lymphatic capillary. As the pressure in the tissue decreases and drainage stops, endothelial cells overlap tightly preventing lymph outflow. Return Mechanisms 8. a. What is the function of lymphatic ducts? Lymphatic ducts returns lymph to the blood. b. Contrast the functions of the right lymphatic duct and the thoracic lymphatic duct. The right lymphatic duct drains the upper right quadrant of the body. The left or thoracic duct drains the rest of the body, the entire upper left quadrant and the entire body below the waist. c. Where do the lymphatic ducts empty into the circulatory system? The right lymphatic duct drains into the right subclavian vein and the thoracic duct empties into the left subclavian vein. 9. What two mechanisms promote lymph movement. The two main mechanisms that promote the return of lymph flow are pumping actions on part of skeletal muscles and respiratory breathing mechanics. + 10. Describe the three steps that result in lymph movement facilitated by muscular pumping. Valves in the vessels maintain flow in one direction. At rest the distal and proximal valves are open and fluid flows towards the heart. When the muscle contracts the fluid is compressed upward through the open proximal valve while the distal valve is closed. After contraction, the proximal valve closes and the distal valve opens and fluid flows into the empty, decompressed vessel. 11. Explain the respiratory pumping mechanism of moving lymph toward the heart. Respiratory mechanisms also promote lymph flow with alternative compression and decompression. Valves again prevent backflow and ensures that fluid flow is unidirectional.. Prior to inhalation, fluid fills the thoracic and abdominal vessels. Inhalation expands the thoracic cavity, compressing the abdominal contents, which in turn compresses the abdominal vessels, Fluid is forced into the thoracic vessels towards the heart. With exhalation, the diaphragm moves upward, and the the abdominal vessels are no longer compressed..