Questions and Answers
What is the primary function of secondary lymphoid organs?
Which of the following is a component of the lymph node medulla?
What is the function of the germinal center in a secondary lymph node follicle?
Which of the following vessels carries lymph from the lymph node and returns it to the blood?
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What is the function of the spleen?
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What is the composition of the lymph node stroma?
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Which of the following is a characteristic of primary lymphoid follicles?
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Which of the following vessels penetrates the capsule of the lymph node on the convex side?
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What are the primary lymphoid organs?
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What is the main function of the spleen in the immune system?
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What is the name given to the parenchyma of the spleen?
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Which of the following components is NOT found in the white pulp of the spleen?
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What is the function of the splenic sinuses (sinusoids) in the red pulp?
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What is the function of MALT (Mucosa-Associated Lymphoid Tissue)?
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Which of these is a secondary lymphoid organ?
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What is the primary function of splenic cords?
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Study Notes
Lymphoid System Outline
- The lymphoid system consists of primary and secondary lymphoid organs
- Primary lymphoid organs: bone marrow and thymus
- Secondary lymphoid organs: lymph nodes, spleen, and mucosa-associated lymphoid tissue (MALT)
Secondary Lymphoid Organs
- Act as filters that trap antigens and expose them to lymphocytes
- Lymph nodes filter lymph, spleen filters blood, and MALT filters antigens that try to cross mucosal surfaces
Lymph Node Components
- Cortex contains lymphoid follicles composed of B cells
- Paracortex contains T cells and high endothelial venules
- Medulla composed of cords containing B cells and macrophages, and sinuses containing reticular fibers, lymph, and circulating cells and antigens
- Stroma composed of reticulin (type III collagen) fibers
Lymph Node Follicles
- Primary follicles consist of small, dark, mature lymphocytes
- Secondary follicles consist of:
- Germinal center: a lighter-staining central area containing larger lymphocytes
- Mantle zone: around germinal center; contains small, dark lymphocytes
Afferent and Efferent Lymphatic Vessels
- Afferent lymphatic vessels penetrate the capsule of the lymph node on the convex side and carry lymph with antigen and cells from sites of infection back to the lymph node
- Efferent lymphatic vessels leave through the hilum and carry lymph with lymphocytes from the lymph node and return it to the blood
Functions of the Spleen
- Filters blood (traps antigens)
- Provides a place for lymphocytes to encounter antigens and become activated
- Removes old red cells and platelets
Structure of the Spleen
- Parenchyma of spleen is called splenic pulp and consists of white pulp and red pulp
- No cortex or medulla are present
- Stroma consists of capsule, trabeculae, and reticular connective tissue
- Hilum contains nerves, arteries, and veins
White Pulp of the Spleen
- Consists of:
- Periarteriolar lymphatic sheaths (PALS): tubule-shaped collections of T cells around arterioles
- Splenic follicles (nodules): similar to secondary follicles in lymph nodes, with an additional marginal zone composed of B cells
Red Pulp of the Spleen
- Consists of:
- Splenic sinuses (sinusoids): leaky vessels lined by specialized endothelial cells and surrounded by rings of reticular fibers
- Splenic cords (cords of Billroth): contain lots of macrophages that eat old or damaged red cells
Mucosa-Associated Lymphoid Tissue (MALT)
- Unencapsulated lymphoid tissue in mucosa and submucosa of digestive, respiratory, reproductive, and urinary systems
- Catches antigens as they try to cross the mucosa and get into the body
- Found in lung and other systems
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Description
This quiz covers the primary and secondary lymphoid organs, their functions and roles in fighting infections. Understand the lymph nodes, spleen, and MALT.