Which of the following respiratory systems is not closely associated with a blood supply? a. the lungs of a vertebrate b. the gills of a fish c. the tracheal system of an insect d. the skin of an earthworm

Blood returning to the mammalian heart in a pulmonary vein drains first into the a. left atrium. b. right atrium. c. left ventricle. d. right ventricle.

Pulse is a direct measure of a. blood pressure. b. stroke volume. c. cardiac output. d. heart rate.

When you hold your breath, which of the following blood gas changes first leads to the urge to breathe? a. rising O2 b. falling O2 c. rising CO2 c, falling CO2

One feature that amphibians and humans have in common is a. the number of heart chambers. b. a complete separation of circuits for circulation. c. the number of circuits for circulation. d. a low blood pressure in the systemic circuit.

If a molecule of CO2 released into the blood in your left toe is exhaled from your nose, it must pass through all of the following except a. the pulmonary vein. b. the trachea. c. the right atrium. d. the right ventricle.

Compared with the interstitial fluid that bathes active muscle cells, blood reaching these cells in arterioles has a a. higher PO2. b. higher PCO2. c. greater bicarbonate concentration. d. lower pH.