Which lymphoid organ serves as the site where T lymphocytes become immunocompetent T cells?
A. thymus gland
B. tonsils
C. thyroid gland
D. spleen
Ans: A. thymus gland
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This figure shows an intestinal villus. The structure indicated by number 1 is a(n)
A. lacteal. B. intestinal vein. C. microvillus. D. flagellum. E. intestinal artery.
What are the only two places in the entire circulatory system at which gas exchange can take place?
a. pulmonary and cardiac capillaries b. pulmonary and the systemic capillaries c. bronchioles and alveoli d. arterial and venous capillaries e. arteries and veins
____________________ is a procedure to help open clogged vessels.?
Fill in the blank(s) with correct word
Which of the following statements regarding control of respiration is correct?
A. The most important signal for regulating ventilation is the H+ concentration of arterial blood. B. At high altitude, a decrease in PCO2 of the blood stimulates an increase in ventilation. C. Increased concentrations of lactic acid stimulate ventilation primarily by acting on peripheral chemoreceptors. D. An increase in the HCO3- concentration in blood stimulates ventilation. E. A slight decrease in arterial PO2 is a stronger stimulus for increased ventilation than is a comparable decrease in arterial PCO2.