Anatomy and Physiology Answer Key

Anatomy and Physiology Answer Key

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Unformatted text preview: elastic and muscle tissue and a thin outer layer of elastic connective tissue. In addition, veins also have valves. 2. (a) Sinusoids differ from capillaries in that they are wider and follow a more convoluted path through the tissue. They are lined with phagocytic cells rather than the usual endothelial lining of capillaries. (b) Capillaries and sinusoids are similar in that they both transport blood from arterioles to venules. 3. (a) Leakage of fluid from capillaries produces tissue fluid, which bathes the tissues, providing oxygen and nutrients as well as a medium for the transport (away) of metabolic wastes, e.g. CO2. (b) Capillary walls are thin enough to allow exchanges. No exchange occurs in arteries and veins because the walls of arteries and veins are too thick. 4. (a) Arteriolar end: Hydrostatic pressure predominates in causing fluid to move out of the capillaries. (b) Venous end: Increased concentration of solutes and reduction in hydrostatic pressure at the venous end of a capillary bed increases the tendency for water and solutes to reenter the capillary. 5. (a) Most tissue fluid finds it way directly back into the capillaries as a result of net inward pressure at the venule end of the capillary bed. (b) Lymph vessels (which parallel the blood system) drain tissue fluid (as lymph) back into the heart, thereby returning it into the main circulation. Aging and the Endocrine System (page 103) 1. (a) Decrease in lean muscle mass (and consequent increase in fat mass). (b) Decrease in bone density (lower rate of bone deposition). 2. After menopause, the ovaries stop responding to FSH and LH, and estrogen levels decline. The pituitary responds to the low estrogen levels by secreting more FSH and LH in an attempt to stimulate estrogen levels. (In premenopausal women, estrogen, and LH and FSH secretion are regulated by negative feedback mechanims). 3. Loss of bone mass. Arteries (page 107) 1. (a) Tunica externa (b) Tunica media 2. (a) Thick, elastic walls are required in order to withstand the high press...
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This document was uploaded on 01/28/2014.

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