21.4–21.11
21.4–The human circulatory system consists of a heart, blood vessels, and blood.

Blood flows from the heart to the tissues of the body and back to the heart again through a series of endothelium-lined blood vessels.

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Q

Why do most fishes swim with their mouths open?

  • a) They do this to take in any food particles suspended in the water.
  • b) This is a cooling mechanism to help regulate body temperature.
  • c) This allows a fish to swim faster.
  • d) This helps prevent infection by mouth parasites.
  • e) They do this to ventilate their gills.

Carbon dioxide transport differs from oxygen transport in the circulatory systems of mammals, because:

  • a) CO2 is transported mostly in the plasma, while O2 is transported mostly in the red blood cells.
  • b) CO2 is transported mostly in the platelets, while O2 is transported mostly in the red blood cells.
  • c) CO2 is transported mostly via the lymphatic system, while O2 is transported mostly in the red blood cells.
  • d) CO2 is bound primarily to receptors within the red blood cell membrane, while O2 is bound primarily to hemoglobin inside the red blood cells.
  • e) CO2 is transported mostly in the plasma, while O2 is transported mostly in hemoglobin within the plasma.

Breathing in birds is more like “breathing” in fishes than in mammals, because:

  • a) water and high-altitude air have similar viscosity.
  • b) oxygen never runs into a dead end.
  • c) both birds and fishes have gill arches.
  • d) the blood vessels in bird lungs, like those in fish gills, are insulated with a fatty coating, reducing heat loss.
  • e) in birds and fishes, but not mammals, the heart pumps in a two-circuit system of blood flow.

Which of the following are the main muscles used in breathing?

  • a) back muscles and thoracic muscles
  • b) intercostal muscles and pectoral muscles
  • c) diaphragm and thoracic muscles
  • d) diaphragm and back muscles
  • e) intercostal muscles and diaphragm

Under resting metabolic conditions, what percentage of oxygen is released from the blood to the tissues?

  • a) 1%
  • b) 75%
  • c) 25%
  • d) 100%
  • e) 50%