The circulatory system

• What is the primary function of the circulatory system?

  To transport substances around the body.
• Why do multicellular organisms need a specialized transport system?

  Because they have a low surface area to volume ratio.
• What are the main components of the circulatory system?

  The heart and blood vessels.
• How does the heart function in the circulatory system?

  The heart pumps blood through blood vessels to different parts of the body.
• What types of blood vessels are involved in the circulatory system?

  Arteries, arterioles, veins, and capillaries.
• What substances does blood transport?

  Respiratory gases, products of digestion, metabolic wastes, and hormones.
• What are the two circuits of the circulatory system?

  One circuit takes blood from the heart to the lungs and back, and the other takes blood around the rest of the body.
• What supplies blood to the heart itself?

  The left and right coronary arteries.
• What are the characteristics of arteries?

  • Carry blood from the heart to the body
  • Thick muscular walls with elastic tissue
  • High pressure maintenance
  • Folded endothelium for stretching
  • Carry oxygenated blood (except pulmonary arteries)
• What is the role of arterioles in the circulatory system?

  • Smaller vessels that branch from arteries
  • Form a network throughout the body
  • Muscles inside arterioles regulate blood flow
• What are the characteristics of veins?

  • Carry blood back to the heart under low pressure
  • Wider lumen than arteries
  • Little elastic or muscle tissue
  • Contain valves to prevent backflow
  • Carry deoxygenated blood (except pulmonary veins)
• How do capillaries facilitate the exchange of substances?

  They are adapted for efficient diffusion with thin walls and proximity to cells.
• What are the adaptations of capillaries for substance exchange?

  • Found near cells for short diffusion pathway
  • Walls are one cell thick
  • Large number of capillaries increases surface area (capillary beds)
• What is tissue fluid and how is it formed?

  Tissue fluid surrounds cells and is formed from small molecules that leave the blood plasma.
• Why can't red blood cells or large proteins leave the capillaries?

  Because they are too large to be pushed out through the capillary walls.
• How does fluid movement occur at the capillary bed?

  1. Hydrostatic pressure is greater in capillaries than in tissue fluid.
  2. Fluid is forced out of capillaries into tissue spaces.
  3. Hydrostatic pressure decreases as fluid leaves.
  4. Water potential is lower at the venule end due to fluid loss and plasma proteins.
  5. Water re-enters capillaries from tissue fluid by osmosis.
• What happens to excess tissue fluid?

  It is drained into the lymphatic system.
• What is the function of the lymphatic system in relation to tissue fluid?

  It transports excess fluid from tissues back into the circulatory system.
• What is the relationship between structure and function in the circulatory system?

  • Structure of blood vessels (thick walls, valves) relates to their function (high pressure, preventing backflow).
  • Capillary structure (thin walls, large surface area) facilitates efficient exchange.
• What is the hydrostatic pressure at the arterial end of a capillary bed?

  1. 1 kPa.
• What is the hydrostatic pressure in the tissue fluid at the capillary bed?

  0.13 kPa.
• What effect does high blood pressure have on capillaries?

  It can lead to the leakage of fluid into the tissue.
• Why is it important to understand the relationship between structure and function in biology?

  It helps in understanding how biological systems operate effectively.