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20 Cards in this Set
- Front
- Back
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Which capsulated lymphoid tissue contain lobules and which do not?
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Lobules: thymus
No lobules: spleen and lymph nodes |
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What is the function of the thymus?
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Produce only T-lymphocytes
Decreases in size with age Is largely replaced by fat and connective tissue Continues to produce T-lymphocytes in adults |
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What is the structure of the thymus?
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Possesses two lobes
Possesses a connective tissue capsule Capsule associated with connective tissue septa that penetrate to the medulla Septa divide the Thymus into incomplete lobules Lobules possess a dark outer ring and a lighter inner medulla Medulla contains "Hassal's" Corpuscles No lymphoid nodules No germinal centers |
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Describe the thymus cortex.
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Dark
Site of T-lymphocyte maturation Cells: subcapsular thymic epithelial cells, thymic cortical epithelial cells, maturing T-cells (developing thymocytes) |
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Describe the thymus medulla.
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Lighter
Site of mature lymphocytes Cells: Hassal's corpuscles, thymic medullary epithelial cells, dendritic cells |
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What are Hassal's Corpuscles?
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Only present in the medulla
Closely packed epithelial cells Release a factor that stimulates thymic dendritic cells to complete maturation of T cells |
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What is the Thymus-Blood barrier?
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Only exists in the cortex
Prevents most circulating antigens from reaching developing T cells Epithelial-reticular cells bound to the capillaries |
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What are the functions of the spleen?
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Located in left superior quadrant
Macrophages present destroy old red blood cells Spleen traps antigens Reservoir for 1/3 of platelets Hematopoiesis takes place there |
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What is the general organization of the spleen?
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Surrounded by a connective tissue capsule (collagen, elastic fibers, smooth muscle)
Trabeculae extend from the capsule and divide the spleen into incomplete compartments No cortex/medulla Parenchyma is made up of reticular fibers supporting the red and white pulp |
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What are the two main components of the spleen?
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Red pulp: rich in red blood cells
White pulp: rich in lymphoid tissue |
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Describe the white pulp of spleen.
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Germinal center
Corona Central artery Periarteriolar lymphoid sheaths |
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What is the marginal zone of spleen?
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Where the red and white pulp interact
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Describe the red pulp of spleen.
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Splenic cord formed by reticular cells
Splenic sinusoid Pennicillar arteries Macrophage sheathed capillaries Circulating blood cells |
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What is the blood flow for the spleen?
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Splenic artery from the celiac trunk
Splenic artery divides into trabecular arteries which follow the trabeculae into parenchyma of the spleen Trabecular arteries divide into central arteries which penetrate the white pulp and are surrounded by periarteriolar lymphoid sheaths Central arteries produce radial arteries while in the white pulp that feed into the marginal zone sinuses Central arteries leave the white pulp and enter the red pulp as penicillar arteries, which either end in the splenic sinusoids or into the red pulp The penicillar arteries and the small capillaries that they produce are sheathed by macrophages, that are responsible for removing damaged RBCs and particles from the blood |
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What are lymph nodes?
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Smallest, most numerous encapsulated lymphoid organs
In line filters of lymph: removes antigens and cellular debris, produce lymphocytes, add antibodies |
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Describe the general organization of lymph nodes.
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Surrounded by a connective tissue capsule
Trabeculae extend into the parenchyma between cortical nodules Outer cortex Inner medulla Hilum (where enters via arteries, leaves via veins and lymph leaves via efferent lymph vessels) |
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Describe the cortex of lymph nodes.
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Outer cortex (B cell rich): lymphatic nodule (germinal center, mantle) and subcapsular/cortical sinus
Inner cortex (T cell rich): lymphatic nodules |
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Describe the medulla of lymph nodes.
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Meullary cords: primarily comprised of macrophages and plasma cells
Medullary sinuses: spaces lined by endothelial cells surrounded by reticular cells and macrophages |
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What is the purpose of sinuses in lymph nodes?
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Filter lymph and direct flow
Mesh of reticular cells and fibers Macrophages and follicular dendritic cells Slows flow of lymph which facilitates antigen removal Lymph is cleared of 90% of antigens and cellular debris |
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What are diagnostic features for the thymus, lymph nodes, spleen, and tonsils?
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Thymus: Hassal's Corpuscles
Lymph nodes: cortical nodules, subcapsular sinus Spleen: central arteries Tonsils: epithelial covering |
