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Lymphoid Organs and Immunity Overview
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1
Question
What is the primary role of lymphoid organs?
Answer
Protect the body by immunological defenses and filtering of fluids.
2
Question
What are the two principal components of lymphoid tissue?
Answer
Reticular tissue (reticular cells and fibers) and free cells (lymphocytes).
3
Question
What is the function of germinal centers in lymph nodes?
Answer
Sites of active B-cell proliferation within secondary nodules.
4
Question
Where are Peyer’s patches located?
Answer
In the wall of the small intestine (ileum), submucosa near the ileocecal junction.
5
Question
What characterizes diffuse lymphoid tissue?
Answer
Diffuse infiltration of lymphocytes mainly in lamina propria of mucous membranes.
6
Question
What is the difference between primary and secondary lymphoid nodules?
Answer
Primary lack germinal centers; secondary have germinal centers with proliferating lymphocytes.
7
Question
What is the hilus of a lymph node?
Answer
The indented region where blood vessels enter/exit the node.
8
Question
What vessels enter and exit a lymph node respectively?
Answer
Afferent lymphatic vessels enter; efferent lymphatic vessels exit.
9
Question
What is the role of the marginal sinus in a lymph node?
Answer
Separates capsule from cortex; entry point for radially directed lymph channels.
10
Question
What type of cells line lymphatic sinuses?
Answer
Reticular cells and littoral (fl reconoce) macrophages with endothelium.
11
Question
What are littoral cells?
Answer
Macrophage-like lining cells of lymphatic sinuses with limited phagocytosis.
12
Question
What is the functional distinction of the cortex vs medulla in lymph nodes?
Answer
Cortex houses nodules with B/T cell zones; medulla has medullary cords and sinuses.
13
Question
What cells predominate the T-cell rich paracortex?
Answer
T lymphocytes.
14
Question
What initiates humoral immune response in lymph nodes?
Answer
Interaction of helper T cells with reactive B lymphocytes.
15
Question
What is the role of post-capillary venules in the lymph node?
Answer
Site of lymphocyte migration from blood into lymph node.
16
Question
What is a hemolymph (hemal) lymph node?
Answer
A lymph node-like structure with blood in sinuses, no afferent/efferent lymphatics.
17
Question
What is the main function of the spleen’s red pulp?
Answer
Removal of defective RBCs and recycling of iron.
18
Question
What structures form the splenic cords?
Answer
Billroth cords; reticular framework with free cells and erythrocytes.
19
Question
What is the marginal zone in the spleen?
Answer
Transitional area between white and red pulp rich in lymphocytes and plasma cells.
20
Question
What is the white pulp in the spleen composed of?
Answer
Periarterial lymphoid sheaths (PALS) and lymphoid nodules around central arteries.
21
Question
What is Malpighian body in the spleen?
Answer
A splenic nodule with central arteriole surrounded by lymphocytes.
22
Question
Which cells predominate in the spleen’s white pulp during immune responses?
Answer
T cells in PALS and B cells in surrounding nodules.
23
Question
What are central arteries in the spleen?
Answer
Arteries that traverse the white pulp and give off capillaries to white pulp.
24
Question
What is the meshwork of reticular fibers in the spleen supported by?
Answer
Reticular cells and reticular fibers.
25
Question
What are splenic sinuses lined by?
Answer
Endothelial cells with unique elongated shape and basal lamina.
26
Question
What is hemocatheresis?
Answer
Removal of aged erythrocytes by macrophages.
27
Question
What are Hassall’s corpuscles?
Answer
Thymic corpuscles in the medulla of the thymus; concentric epithelial reticular cell layers.
28
Question
Where do thymic T lymphocytes mature?
Answer
In the thymus (thymocytes).
29
Question
What is the blood-thymus barrier?
Answer
Barrier restricting macromolecules from cortex; formed by endothelial and epithelial barriers.
30
Question
What happens in thymic medulla with mature T cells?
Answer
Mature T cells exit to populate other lymphoid tissues.