Arterioles receive blood from arteries, which are vessels with a much larger lumen. as their own lumen averages just 30 micrometers or less, arterioles are critical in slowing down—or resisting—blood flow. the arterioles can also constrict or dilate, which varies their what?

• Correct Answer: resistance
• advantage
• osmosis
• gravity

Explanation: Chapter 20 1 Water. 3 A 5 C 7 C 9 A 11 D 13 B 15 A 17 C 19 A 21 C 23 D 25 D 27 C 28 Arterioles receive blood from arteries, which are vessels with a much larger lumen. As their own lumen averages just 30 micrometers or less, arterioles are critical in slowing down—or resisting—blood flow. The arterioles can also constrict or dilate, which varies their resistance, to help distribute blood flow to the tissues. 30 This is a venule. 32 People who stand upright all day and are inactive overall have very little skeletal muscle activity in the legs. Pooling of blood in the legs and feet is common. Venous return to the heart is reduced, a condition that in turn reduces cardiac output and therefore oxygenation of tissues throughout the body. This could at least partially account for the patient’s fatigue and shortness of breath, as well as her “spaced out” feeling, which commonly reflects reduced oxygen to the brain. 34 False. The plasma proteins suspended in blood cannot cross the semipermeable capillary cell membrane, and so they remain in the plasma within the vessel, where they account for the blood colloid osmotic pressure. 36 Nitric oxide is a very powerful local vasodilator that is important in the autoregulation of tissue perfusion. If it were not broken down very quickly after its release, blood flow to the region could exceed metabolic needs. 38 The gonadal veins drain the testes in males and the ovaries in females. 40 Angiogenesis inhibitors are drugs that inhibit the growth of new blood vessels. They can impede the growth of tumors by limiting their blood supply and therefore their access to gas and nutrient exchange.

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