Lymphoid System
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Questions and Answers

What is the primary function of the spleen during fetal life?

Hemopoiesis of blood elements

What type of fibers are present in the capsule of the spleen?

Dense C.T and smooth muscle fibers

What is the function of the spleen in terms of blood filtration?

Filtration of bacteria, foreign bodies, old RBCs, WBCs, and platelets

What is the role of the marginal zone in the white pulp of the spleen?

<p>Rich in T-lymphocytes and plasma cells</p> Signup and view all the answers

What is the role of the trabeculae in the spleen?

<p>Radiating from the hilum and carrying blood vessels</p> Signup and view all the answers

What is the function of the spleen in terms of immune response?

<p>Production of lymphocytes and role in humoral and cell-mediated immunity</p> Signup and view all the answers

What is the primary function of the lymphoid system?

<p>Protection of the body against invading microorganisms or foreign bodies</p> Signup and view all the answers

What are the two main types of lymphoid organs?

<p>Primary or central lymphoid organs and secondary or peripheral lymphoid organs</p> Signup and view all the answers

What is the main function of the thymus?

<p>Site for development and differentiation of T lymphocytes</p> Signup and view all the answers

What is the structure of the thymus?

<p>It consists of a stroma and a parenchyma</p> Signup and view all the answers

What are Hassall's corpuscles?

<p>Large rounded structures composed of concentric layers of epithelial reticular cells around a central hyaline acidophilic mass</p> Signup and view all the answers

What is the function of thymic hormones?

<p>Development and differentiation of T lymphocytes</p> Signup and view all the answers

What is the blood-thymic barrier?

<p>Formed by the wall of blood capillaries, the surrounding APCs, and the surrounding phagocytic cells</p> Signup and view all the answers

Where do B and T lymphocytes develop?

<p>Primary lymphoid organs (bone marrow and thymus)</p> Signup and view all the answers

Study Notes

The Lymphoid (Immune) System

  • Responsible for protecting the body against invading microorganisms or foreign bodies
  • Distributed throughout the body and consists of aggregations of lymphocytes (B and T lymphocytes) and epithelial cells

Lymphatic Tissues (Organs)

  • Classified into:
    • Primary or central lymphoid organs (thymus and bone marrow): where B & T lymphocytes develop
    • Secondary or peripheral lymphoid organs (spleen, lymph nodes, tonsils, appendix, Peyer's patches, and solitary lymphatic nodules): where B & T lymphocytes settle

Thymus

  • Flattened bilobed organ lying behind the sternum
  • Large in infants, grows until puberty, then diminishes in size
  • Consists of:
    • Stroma: capsule, trabeculae, and connective tissue
    • Parenchyma: outer dark cortex and inner pale medulla
  • Cortex:
    • Contains thymocytes (T lymphocytes), epithelial reticular cells (APCs), and macrophages
  • Medulla:
    • Contains thymocytes (T lymphocytes), epithelial reticular cells (APCs), macrophages, and Hassall's corpuscles
  • Functions:
    • Site for development and differentiation of T lymphocytes
    • Production of T lymphocytes
    • Secretion of thymic hormones
    • Formation of Blood-thymic barrier

Spleen

  • Single intra-abdominal organ covered by peritoneum
  • Consists of:
    • Stroma: capsule, trabeculae, and reticular stroma
    • Parenchyma: white pulp and red pulp
  • White pulp:
    • Formed of 4 zones from inside to outside: thymus-dependent zone, germinal center zone, follicular zone, and marginal zone
  • Red pulp:
    • Consists of blood sinusoids and splenic cords
  • Functions:
    • Hemopoiesis of blood elements during fetal life
    • Production of lymphocytes
    • Destruction of abnormal, damaged, and aged blood cells
    • Blood filtration
    • Storage of blood

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Description

Quiz about the immune system, its functions, and components. Learn about primary and secondary lymphoid organs, and their roles in protecting the body against infections.

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