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Blood Vessel Structure and Function - Anatomy & Physiology

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Terms in this set (20)

  • What are the three main types of blood vessels and their primary functions?
    Arteries carry blood away from the heart (usually oxygenated), capillaries serve cellular needs by direct exchange, and veins carry blood toward the heart (usually deoxygenated).
  • What are the three layers (tunics) of most blood vessel walls?
    Tunica intima (innermost), tunica media (middle, smooth muscle and elastin), and tunica externa (outermost, collagen fibers).
  • Describe the tunica intima.
    Innermost layer with endothelium (simple squamous epithelium) lining the lumen, continuous with the heart's endocardium, providing a slick surface to reduce friction.
  • What is the function of the tunica media?
    Middle layer composed mostly of smooth muscle and elastin; controls vasoconstriction and vasodilation to regulate blood flow and pressure.
  • What composes the tunica externa and its function?
    Outermost layer made of loose collagen fibers that protect, reinforce, and anchor vessels; contains nerve fibers, lymphatic vessels, and in large vessels, the vasa vasorum.
  • What distinguishes elastic arteries from other arteries?
    Thick-walled with large lumens, rich in elastin in all tunics, act as pressure reservoirs to expand and recoil, maintaining continuous blood flow.
  • What are muscular arteries and their key features?
    Also called distributing arteries; have thick tunica media with more smooth muscle and less elastin; actively regulate blood flow via vasoconstriction.
  • What are arterioles and their role?
    Smallest arteries controlling blood flow into capillary beds through vasodilation and vasoconstriction; also called resistance arteries.
  • Describe the structure and function of capillaries.
    Microscopic vessels with thin tunica intima; allow exchange of gases, nutrients, wastes between blood and tissues.
  • What are pericytes in capillaries?
    Spider-shaped stem cells that stabilize capillary walls, control permeability, and assist in vessel repair.
  • Name and describe the three types of capillaries.
    Continuous: least permeable, tight junctions; fenestrated: pores for filtration/absorption; sinusoidal: large gaps, incomplete basement membrane, found in liver, bone marrow.
  • What is a capillary bed and its components?
    Network of capillaries between arterioles and venules; includes terminal arteriole, true capillaries, and postcapillary venule.
  • How is blood flow regulated in capillary beds?
    By diameter of terminal arteriole and precapillary sphincters, controlled by local chemical signals and vasomotor nerves.
  • What is a vascular shunt in capillary beds?
    A channel (metarteriole and thoroughfare channel) that directly connects arteriole to venule, bypassing true capillaries.
  • Describe veins and their structural differences from arteries.
    Veins have thinner walls, larger lumens, thinner tunica media, thicker tunica externa; function as blood reservoirs with valves to prevent backflow.
  • What adaptations help veins return blood to the heart despite low pressure?
    Large lumens reduce resistance, venous valves prevent backflow, and venous sinuses provide thin-walled channels.
  • What are varicose veins and their causes?
    Dilated, painful veins due to incompetent valves; caused by heredity, prolonged standing, obesity, or pregnancy.
  • What are vascular anastomoses?
    Interconnections of blood vessels providing alternate pathways for blood flow; arterial anastomoses ensure continuous flow if one artery is blocked.
  • Where are arterial anastomoses commonly found and absent?
    Common in joints, abdominal organs, brain, heart; absent in retina, kidneys, and spleen.
  • What are venous anastomoses?
    Abundant connections between veins that prevent blood flow blockage if one vein is occluded.