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Circulatory Physiology and Blood Vessel Structure

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Terms in this set (24)

  • What are the three main layers of blood vessel walls?
    Tunica intima (inner layer), tunica media (middle layer with smooth muscle), and tunica externa (outer layer with connective tissue).
  • What is the primary function of arteries?
    Arteries carry blood away from the heart and have thick, elastic walls to absorb pressure waves from heartbeats.
  • How do arterioles regulate blood flow?
    Arterioles control blood flow into capillary beds by vasoconstriction and vasodilation, adjusting diameter to regulate resistance.
  • What is the role of capillaries in circulation?
    Capillaries are the smallest blood vessels where exchange of gases, nutrients, and wastes occurs between blood and tissues.
  • Describe the structure of capillaries.
    Capillaries consist of a single layer of endothelial cells and a thin basement membrane, lacking tunica media and externa.
  • What are the three types of capillaries?
    Continuous (muscle), fenestrated (kidney, endocrine glands), and sinusoids (liver, spleen, bone marrow).
  • What is the function of precapillary sphincters?
    Precapillary sphincters regulate blood flow into capillaries by opening or closing in response to tissue needs.
  • How does blood velocity change through the vascular system?
    Blood velocity is fastest in the aorta, slows down in capillaries due to large cross-sectional area, and increases again in veins.
  • What is the significance of the large cross-sectional area of capillaries?
    The large total cross-sectional area slows blood flow, allowing adequate time for exchange between blood and tissues.
  • What is the role of metarterioles?
    Metarterioles act as arteriovenous shunts that can bypass capillary beds and regulate blood flow to multiple capillaries.
  • How do veins differ structurally from arteries?
    Veins have thinner walls, larger lumens, less elastic tissue, and contain valves to prevent backflow.
  • What mechanisms assist venous return to the heart?
    Venous return is aided by the muscular pump, respiratory pump, and venoconstriction under sympathetic control.
  • What is autoregulation in blood flow?
    Autoregulation is the intrinsic adjustment of blood flow to tissues by changing arteriole diameter independent of mean arterial pressure.
  • What are the two types of autoregulation controls?
    Metabolic controls (respond to tissue chemical changes) and myogenic controls (vascular smooth muscle response to stretch).
  • How do metabolic controls regulate blood flow?
    Metabolic controls cause vasodilation in response to low O2, high H+, K+, adenosine, prostaglandins, and inflammatory chemicals.
  • What is the myogenic response in blood vessels?
    Vascular smooth muscle constricts when stretched by increased pressure and dilates when pressure decreases to maintain constant perfusion.
  • What happens during long-term autoregulation?
    Long-term autoregulation involves angiogenesis, increasing vessel number and size to meet tissue nutrient demands.
  • How does blood flow change during exercise?
    Blood flow increases to skeletal muscles, heart, and lungs; decreases to nonessential organs; brain flow remains constant.
  • What cardiovascular adaptations occur during hemorrhaging?
    Short-term: increase heart rate, vasoconstriction, venoconstriction. Long-term: fluid retention, increased thirst, and red blood cell production.
  • What is the Frank–Starling principle?
    Increased venous return stretches the heart atria, leading to increased cardiac output during exercise.
  • How does the cardiovascular system prioritize blood flow to the brain?
    Brain blood flow is maintained by cerebral vessel dilation when peripheral vessels constrict to ensure high oxygen supply.
  • What causes a cerebrovascular accident (stroke)?
    Blockage or rupture of a cerebral artery that stops blood flow to brain tissue.
  • How is blood flow to the lungs regulated?
    Pulmonary vessels dilate in response to high alveolar O2 and constrict when O2 is low.
  • What are the effects of regular moderate exercise on cardiovascular health?
    Reduces LDL cholesterol, slows plaque formation, lowers heart attack risk, and improves recovery after cardiac events.