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anim_capillary_exchange_answer_key.doc

Uploaded: 4 years ago
Contributor: jan
Category: Anatomy
Type: Other
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Filename:   anim_capillary_exchange_answer_key.doc (167 kB)
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Credit Cost: 1
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Transcript
Capillary Exchange To complete this worksheet, select: Module: Distribution Activity: Animations Title: Capillary Exchange Introduction 1. Describe the relative movement of oxygen, carbon dioxide, and other wastes, between capillaries and living cells. The capillaries are the sites that permit the exchange of nutrients and wastes between the blood and tissues cells. Oxygen and nutrients move out of the blood into the cells while carbon dioxide and metabolic wastes move out of the tissues into the blood. Mechanisms of Capillary Exchange 2. a. Describe the importance of diffusion as a method of capillary exchange. Diffusion is the most important means of transport for capillary exchange. b. Describe movement of small or lipid soluble molecules across the endothelial cell membrane. Small lipid-soluble molecules move easily across the capillary membrane. c. Describe movement of medium-sized, or lipid insoluble soluble substances across the endothelial cell membranes. The medium size, lipid-insoluble substances such as glucose and amino acids move across intercellular clefts and fenestrations 3. Describe transcytosis. Include endocytosis and exocytosis in your explanation. Transcytosis is used to transport small amounts of large, lipid-insoluble molecules, such as large proteins. Substances packaged in vesicles move by entering the cell via endocytosis and leave by employing exocytosis. 4. a. What does bulk flow transport? This is the movement of large volumes of ions, molecules or particles between the blood and cells. b. How do pressure gradients affect bulk flow? Bulk flow is employed whenever the pressure gradients push water and dissolved solutes out or into the capillary. c. Describe the function of capillary fenestrations. To pass large amounts of fluids and substances out of the capillary without having to go through the endothelial cell. Bulk Flow 5. Describe the correlation between bulk flow and the relative volumes of blood and interstitial fluids. Fenestrated capillaries allow for more bulk flow. Bulk flow helps regulate the relative volumes of blood and interstitial fluid. 6. Explain each of the following factors that determine the net direction of capillary exchange. Blood Hydrostatic Pressure (BHP) - This pushes fluid out of the capillaries and promotes filtration. Blood Colloid Osmotic Pressure (BCOP) – This acts to pull fluid into the capillary and promotes reabsorption. Interstitial Fluid Osmotic Pressure (IFOP) – This is the slight pull of fluids toward the interstitium promoting filtration. Interstitial Fluid Hydrostatic Pressure (IFHP) – Under normal conditions this has no effect since this pressure is near or about zero. 7. Define Net Filtration Pressure (NFP). NFP is the force promoting filtration minus the force promoting reabsorption. 8. a. Describe filtration and reabsorption pressures at each of the following capillary locations. Arterial End – Here, the filtration pressures are stronger where the end result is net filtration. Venous End – Here, the reabsorption pressures are stronger with the net result being net reabsorption. b. How much of the water that is filtered out of the arterial end of the capillary is reabsorbed at the venous end? About 90% of the fluid that is filtered at the arterial end is reabsorbed at the venous end. What happens to the interstitial fluid not reabsorbed into the venous capillaries? The remaining fluid that is not reabsorbed drains into lymphatic capillaries to form lymph. 10. a. Define edema. Swelling caused by the abnormal buildup of interstitial fluid. Name four major causes of edema. • increased capillary hydrostatic pressure • increased capillary permeability. • decreased blood colloidal osmotic pressure. • blockage of lymphatic drainage. Blood Velocity 11. a. Describe the relationship between blood velocity and blood vessel cross-sectional area. Blood velocity is inversely related to the total cross-sectional area. Blood velocity decreases when the total cross-sectional area of blood vessel increases. b. Why is slow blood velocity important in the capillaries? Slow blood velocity allows a greater time for the exchange of materials between the tissue and blood via diffusion. 12. Describe blood velocity patterns as blood moves away from, and then back toward, the heart. Blood velocity slows as blood travels away from the heart and increases as it travels towards the heart.

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