The Circulatory System
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Questions and Answers

What is the primary function of the circulatory system?

  • To filter waste from the blood
  • To regulate body temperature
  • To produce energy for the body
  • To transport blood and lymph to and from the tissues of the body (correct)
  • Which of the following blood vessels is responsible for carrying blood away from the heart?

  • Veins
  • Venules
  • Capillaries
  • Arteries (correct)
  • What is the location of exchange between blood and interstitial fluid?

  • Veins
  • Capillaries (correct)
  • Venules
  • Arterioles
  • What is the outermost layer of the blood vessel wall?

    <p>Tunica externa</p> Signup and view all the answers

    What is the layer of elastic fibers in the outer margin of the tunica intima called?

    <p>Internal elastic lamina</p> Signup and view all the answers

    What separates the tunica media from the tunica externa in some vessels?

    <p>External elastic lamina</p> Signup and view all the answers

    What is the layer of the blood vessel wall that contains concentric sheets of smooth muscle?

    <p>Tunica media</p> Signup and view all the answers

    What is the circulatory system composed of?

    <p>Both the cardiovascular and lymphatic systems</p> Signup and view all the answers

    What is the main function of postcapillary venules and muscular venules?

    <p>To collect blood from capillaries</p> Signup and view all the answers

    Which of the following is a characteristic of medium-sized veins?

    <p>Presence of vein valves</p> Signup and view all the answers

    What is the primary function of vein valves?

    <p>To prevent blood from flowing backward</p> Signup and view all the answers

    What is a characteristic of large veins?

    <p>Thick tunica externa and longitudinal bundles of smooth muscle</p> Signup and view all the answers

    What is a key difference between arteries and veins?

    <p>Arteries have thicker walls and higher blood pressure</p> Signup and view all the answers

    What is a characteristic of the lumen of a collapsed artery?

    <p>Small and round</p> Signup and view all the answers

    What is a characteristic of muscular venules?

    <p>Diameter of ≤1 mm</p> Signup and view all the answers

    Which of the following is a characteristic of both arteries and veins?

    <p>Presence of elastic fibers</p> Signup and view all the answers

    What is the main component of the tunica externa in large arteries and veins?

    <p>Collagen fibers</p> Signup and view all the answers

    What is the function of the vasa vasorum?

    <p>To supply blood to the vascular walls</p> Signup and view all the answers

    What is a characteristic of capillaries?

    <p>They have a thin wall and a small diameter</p> Signup and view all the answers

    What type of capillary is found in the CNS and thymus?

    <p>Specialized continuous capillary</p> Signup and view all the answers

    What is the function of fenestrated capillaries?

    <p>To permit rapid exchange of water and larger solutes</p> Signup and view all the answers

    What is a characteristic of sinusoids?

    <p>They have a wide space between endothelial cells</p> Signup and view all the answers

    What is the function of arteriovenous anastomoses?

    <p>To bypass the capillary bed and regulate body temperature</p> Signup and view all the answers

    What is a characteristic of elastic arteries?

    <p>They have a large number of elastic fibers</p> Signup and view all the answers

    What is a characteristic of muscular arteries?

    <p>They have a large number of muscle cells</p> Signup and view all the answers

    What is the function of veins?

    <p>To collect blood from capillaries in tissues and organs</p> Signup and view all the answers

    Study Notes

    The Circulatory System

    • The circulatory system is a transport system that carries blood and lymph to and from the tissues of the body.
    • The circulatory system consists of the cardiovascular system and the lymphatic system.

    Cardiovascular System

    • The cardiovascular system includes the heart and vessels.
    • The cardiovascular system is composed of two main parts: macrovasculature (>0.1mm) and microvasculature (interchanges).

    Blood Vessels

    • There are five classes of blood vessels:
      • Arteries: carry blood away from the heart.
      • Arterioles: smallest branches of arteries.
      • Capillaries: smallest blood vessels, location of exchange between blood and interstitial fluid.
      • Venules: collect blood from capillaries.
      • Veins: return blood to the heart.

    Structure of Blood Vessels

    • The wall of blood vessels is composed of three layers called tunics:
      • Tunica intima: innermost layer, includes endothelial lining and connective tissue layer.
      • Tunica media: middle layer, contains smooth muscle and elastic fibers.
      • Tunica externa: outer layer, contains connective tissue and elastic fibers.

    Capillaries

    • Capillaries are the smallest blood vessels.
    • They have small diameter and thin walls.
    • Chemicals and gases diffuse across walls.
    • No tunica media and externa.
    • Endothelial cell inside thin basal lamina and pericytes.
    • There are three types of capillaries:
      • Continuous capillaries: have complete endothelial lining, found in all tissues except epithelia and cartilage.
      • Fenestrated capillaries: have pores in endothelial lining, permit rapid exchange of water and larger solutes.
      • Discontinuous capillaries (sinusoids): have enlarged diameter, endothelial cells with wide space, and basal lamina is discontinuous.

    Arteriovenous Anastomoses

    • Direct connections between arterioles and venules.
    • Bypass the capillary bed.
    • Endothelium lies directly upon a specialized tunica media comprising a sphincter.
    • Are in skeletal muscle and skin of the hands and feet, and tissue that metabolic activity is intermittent (thyroid and digestive system).
    • Serve a thermoregulatory function.

    Arteries

    • Arteries change from elastic arteries to muscular arteries to arterioles.
    • Elastic arteries: large vessels, tunica media has many elastic fibers and few muscle cells.
    • Muscular arteries: medium-sized, tunica media has many muscle cells.
    • Arterioles: small, have little or no tunica externa, and thin or incomplete tunica media.

    Veins

    • Collect blood from capillaries in tissues and organs.
    • Return blood to the heart.
    • There are three categories of veins based on size:
      • Small veins or venules: very small veins, collect blood from capillaries.
      • Medium-sized veins: have tunica intima, thin tunica media, and tunica externa with longitudinal bundles of elastic fibers.
      • Large veins: have all three tunica layers, thin tunica media, and thick tunica externa.

    Vein Valves

    • Valves are an important feature of large and medium veins.
    • Folds of tunica intima, rich in elastic fibers, and covered on both sides by endothelium.
    • Prevent blood from flowing backward.
    • Compression pushes blood toward the heart.

    Comparison of Arteries and Veins

    • Arteries and veins run side-by-side.
    • Arteries have thicker walls and higher blood pressure.
    • Arteries are more elastic.
    • Veins have a higher content of collagen than arteries.
    • Collapsed artery has a small, round lumen, while a vein has a large, flat lumen.
    • Veins have valves.
    • Veins are larger in diameter and have thinner walls.

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    Description

    Learn about the circulatory system, its functions, and components, including the cardiovascular system and lymphatic system.

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