Circulatory System

• What does a closed, double circulatory system mean?

  Blood is confined to vessels and passes twice through the heart for each complete circuit of the body.
• What would happen if the body had a single circulatory system?

  The blood pressure would be reduced, leading to slow circulation that cannot accommodate mammals' high rate of metabolism.
• What does blood transport?

  Respiratory gases, products of digestion, metabolic wastes, and hormones.
• Compare the physical features of the atrium and the ventricle.


  • Both are elastic.
  • Atrium: thin-walled.
  • Ventricle: much thicker muscular wall.
• Why do ventricles have thick walls?

  Because they must strongly contract to pump blood to the lungs or the body.
• What are the names of the right atrioventricular valve and the left one?

  Right = bicuspid, left = tricuspid.
• What are the roles of the aorta, vena cava, pulmonary artery, and pulmonary vein?

  • Aorta: carries oxygenated blood to all parts of the body except the lungs.
  • Vena cava: brings deoxygenated blood back from the tissues of the body (except lungs).
  • Pulmonary artery: carries deoxygenated blood to the lungs.
  • Pulmonary vein: brings oxygenated blood back from the lungs.
• What is the blood supply for the liver called?


  Hepatic.
• What is the blood supply for the kidneys called?


  Renal.
• What is tissue fluid?

  A watery liquid that surrounds cells, containing glucose, amino acids, fatty acids, dissolved ions, and oxygen.
• Why doesn't tissue fluid contain red blood cells or big proteins?

  Because they are too large to be pushed out through the capillary walls.
• How is tissue fluid useful to the body?

  It supplies glucose, amino acids, fatty acids, ions, and oxygen to tissues and receives CO2 and other waste materials from tissues.
• Describe the formation of tissue fluid.

  1. Blood from arterioles enters capillaries with high hydrostatic pressure.
  2. This pressure pushes water and small molecules out through fenestrations into surrounding spaces (ultrafiltration).
  3. Large proteins and red blood cells remain in the capillaries.
  4. The fluid that leaves is called tissue fluid, which bathes surrounding cells.
  5. As fluid leaves, hydrostatic pressure decreases in the capillaries.
  6. Lower pressure at the venule end allows some water to re-enter by osmosis.
  7. Leftover tissue fluid is removed by the lymphatic system.