21.3 Primary Lymphoid Structures
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Questions and Answers

At what age does the thymus reach its maximum weight?

  • Puberty (correct)
  • Infancy
  • Young adulthood
  • Adolescence

    • What happens to the cells within the thymus after it reaches its maximum size?

  • They begin to regress (correct)
  • They multiply rapidly
  • They stay the same size
  • They grow larger

    • What replaces much of the thymic tissue after it regresses?

  • Blood cells
  • Adipose connective tissue (correct)
  • Muscle tissue
  • Nervous tissue

    • Apart from lymphoid cells, what other type of tissue is found in the thymus?

    <p>Epithelial tissue</p> Signup and view all the answers

    Which hormone is NOT produced and secreted by the thymus?

    <p>Insulin</p> Signup and view all the answers

    In a child, how many thymic lobes are present and how are they surrounded?

    <p>Two lobes, each surrounded by a connective tissue capsule</p> Signup and view all the answers

    Where is red bone marrow located in adults?

    <p>Within trabeculae in portions of spongy bone within the skeleton</p> Signup and view all the answers

    What is the primary function of red bone marrow?

    <p>Hematopoiesis (production of formed elements)</p> Signup and view all the answers

    Which of the following is NOT considered a formed element produced in red bone marrow?

    <p>Plasma cells</p> Signup and view all the answers

    Where must T-lymphocytes migrate to complete their maturation?

    <p>Thymus</p> Signup and view all the answers

    What are the two major types of lymphocytes mentioned in the text?

    <p>B-lymphocytes and T-lymphocytes</p> Signup and view all the answers

    What type of cells must migrate to the thymus after being formed in red bone marrow?

    <p>T-lymphocytes</p> Signup and view all the answers

    Why are T-lymphocytes named as such?

    <p>Because they complete their maturation in the thymus.</p> Signup and view all the answers

    Why do B-lymphocytes have the 'B' in their name?

    <p>From their maturation in the bursa of fabricius.</p> Signup and view all the answers

    What is the primary function of the thymus?

    <p>Maturation of T-lymphocytes</p> Signup and view all the answers

    Where do immature T-lymphocytes migrate to complete their maturation?

    <p>Thymus</p> Signup and view all the answers

    Why do humans lack the bursa of fabricius?

    <p>Because B-lymphocytes mature in the bone marrow</p> Signup and view all the answers

    What is the function of red bone marrow?

    <p>Development of formed elements through hematopoiesis</p> Signup and view all the answers

    Where are trabeculae found in the thymic lobes?

    <p>Subdividing the lobes into lobules</p> Signup and view all the answers

    What is the primary composition of both the outer cortex and inner medulla of a thymic lobule?

    <p>Epithelial tissue infiltrated with T-lymphocytes</p> Signup and view all the answers

    What is the main function of the epithelial cells in the thymus?

    <p>To secrete thymic hormones that aid in T-lymphocyte maturation</p> Signup and view all the answers

    Why is the thymus described as a lymphoepithelial organ?

    <p>Because it contains both lymphoid cells and epithelial tissue</p> Signup and view all the answers

    Where do mature T-lymphocytes reside within a thymic lobule?

    <p>In the inner medulla</p> Signup and view all the answers

    What is the approximate maximum weight of the thymus in children?

    <p>30 to 50 grams</p> Signup and view all the answers

    What type of tissue replaces much of the thymic tissue after it regresses?

    <p>Connective tissue</p> Signup and view all the answers

    What is the primary function of the epithelial tissue found in the thymus?

    <p>To produce and secrete hormones</p> Signup and view all the answers

    How many thymic lobes are present in a child's thymus?

    <p>2</p> Signup and view all the answers

    What is the main function of the thymus?

    <p>To house and mature T-lymphocytes</p> Signup and view all the answers

    What is the composition of the outer cortex and inner medulla of a thymic lobule?

    <p>Both lymphoid cells and epithelial cells</p> Signup and view all the answers

    Which of the following is NOT a location for red bone marrow in adults?

    <p>Phalanges</p> Signup and view all the answers

    What is the unique step required by T-lymphocytes in their maturation?

    <p>They must migrate to the thymus</p> Signup and view all the answers

    Which of the following is NOT considered a formed element produced in red bone marrow?

    <p>Fibroblasts</p> Signup and view all the answers

    What is the process of production of formed elements called?

    <p>Hematopoiesis</p> Signup and view all the answers

    Which of the following is NOT a major type of lymphocyte mentioned in the text?

    <p>Natural killer cells</p> Signup and view all the answers

    After being produced in the red bone marrow, where do most formed elements move directly?

    <p>The blood</p> Signup and view all the answers

    What is the reason for the name 'T-lymphocytes'?

    <p>They require the thymus gland for maturation.</p> Signup and view all the answers

    Why were B-lymphocytes given their name?

    <p>They mature in the bursa of fabricius in birds.</p> Signup and view all the answers

    What is the primary function of the thymus?

    <p>Maturation of T-lymphocytes</p> Signup and view all the answers

    Where do immature T-lymphocytes originate from before migrating to the thymus?

    <p>Bone marrow</p> Signup and view all the answers

    What is the primary function of red bone marrow?

    <p>Production of formed elements through hematopoiesis</p> Signup and view all the answers

    What cells are primarily responsible for the maturation of T-lymphocytes within the thymus?

    <p>Epithelial cells</p> Signup and view all the answers

    What structures subdivide the thymic lobes into lobules?

    <p>Trabecular extensions called trabeculae or septa</p> Signup and view all the answers

    Which part of a thymic lobule contains immature T-lymphocytes?

    <p>Cortex</p> Signup and view all the answers

    What type of cells secrete thymic hormones that participate in T-lymphocyte maturation?

    <p>Epithelial cells</p> Signup and view all the answers

    What term is used to describe the thymus due to its composition of lymphoid cells and epithelial tissue?

    <p>Lymphoepithelial organ</p> Signup and view all the answers

    Where are the details of T-lymphocyte maturation described?

    <p>In section 22.5</p> Signup and view all the answers

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