Which of the following is a characteristic of slow-twitch oxidative skeletal muscle fibers?
A) few mitochondria only
B) long contraction duration and high capillary density
C) high capillary density only
D) long contraction duration only
E) long contraction duration, few mitochondria, and high capillary density
B) long contraction duration and high capillary density
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The primary goal of the immune response is
A. removal of antibodies from lymph and lymphatic organs. B. reduction of the number of circulating memory lymphocytes. C. maintenance of the proper ionic balance between lymph and blood. D. stimulation of mitotic activity in order to replace cells damaged by infection. E. destruction or inactivation of pathogens and foreign material.
Which of the following is NOT a step in preparing a wet-mount slide?
A) Using tweezers or your fingers, touch the water stain with the edge of the coverslip. B) Place the specimen on the slide and add a small drop of water to it. C) Do not use a coverslip with a wet-mount preparation. D) Use the coarse adjustment knob to move the objective lens as close to the specimen as possible without touching the slide.
Why is the blood-testis barrier important?
A) because spermatozoa and developing cells produce surface antigens that are recognized as foreign by the immune system B) because some blood contents are toxic to the spermatozoa C) because immature sperm cells lose their motility when they encounter any blood component D) Actually, the blood-testis barrier has no function.
If 20% of the air is composed of O2, the partial pressure of oxygen at an altitude of 20,000 feet where atmospheric pressure is 350 mm Hg is
a. 20 mm Hg b. 760 mm Hg c. 70 mm Hg d. 350 mm Hg e. 152 mm Hg