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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?
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What is the role of the trabeculae in the spleen?
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What is the function of the spleen in terms of immune response?
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What is the primary function of the lymphoid system?
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What are the two main types of lymphoid organs?
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What is the main function of the thymus?
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What is the structure of the thymus?
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What are Hassall's corpuscles?
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What is the function of thymic hormones?
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What is the blood-thymic barrier?
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Where do B and T lymphocytes develop?
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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.
