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Questions and Answers
What is the primary function of high endothelial venules (HEVs) in lymph nodes?
What is the primary function of high endothelial venules (HEVs) in lymph nodes?
What is the order of lymph flow through a lymph node?
What is the order of lymph flow through a lymph node?
What is the purpose of the paracortex in a lymph node?
What is the purpose of the paracortex in a lymph node?
What is the ultimate destination of lymphocytes that enter the lymph node?
What is the ultimate destination of lymphocytes that enter the lymph node?
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What is the function of the reticular fibers in the stroma of the lymph node?
What is the function of the reticular fibers in the stroma of the lymph node?
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What is the region between the cortex and medulla of a lymph node called?
What is the region between the cortex and medulla of a lymph node called?
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What is the purpose of the afferent lymphatic vessels in relation to lymph nodes?
What is the purpose of the afferent lymphatic vessels in relation to lymph nodes?
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What is the site where lymphocytes enter the lymph node through the wall of high endothelial venules (HEVs)?
What is the site where lymphocytes enter the lymph node through the wall of high endothelial venules (HEVs)?
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What is the primary function of the lymphoid nodule/follicle?
What is the primary function of the lymphoid nodule/follicle?
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What type of cells can be found in the germinal center of a lymphoid nodule/follicle?
What type of cells can be found in the germinal center of a lymphoid nodule/follicle?
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What is the function of the marginal zone in a lymphoid nodule/follicle?
What is the function of the marginal zone in a lymphoid nodule/follicle?
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What cell type is responsible for 'education' of lymphocytes in the thymus?
What cell type is responsible for 'education' of lymphocytes in the thymus?
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What is the composition of the cortical region of the thymus?
What is the composition of the cortical region of the thymus?
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What structure separates the lobules of the thymus?
What structure separates the lobules of the thymus?
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What is the primary function of the thymus?
What is the primary function of the thymus?
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What type of cells can be found in the medulla of the thymus?
What type of cells can be found in the medulla of the thymus?
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What is the function of the strands of basal lamina in the splenic sinus?
What is the function of the strands of basal lamina in the splenic sinus?
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What type of cells are found in the marginal zone of the spleen?
What type of cells are found in the marginal zone of the spleen?
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What is the location of the marginal zone in the spleen?
What is the location of the marginal zone in the spleen?
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What is unique about the wall of the splenic sinuses?
What is unique about the wall of the splenic sinuses?
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What is the source of blood in the marginal zone?
What is the source of blood in the marginal zone?
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What happens to circulating T and B lymphocytes when they enter the spleen?
What happens to circulating T and B lymphocytes when they enter the spleen?
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What is the primary function of FDCs in germinal centers?
What is the primary function of FDCs in germinal centers?
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What is the origin of FDCs?
What is the origin of FDCs?
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What is the function of lymph nodes in regards to T cells?
What is the function of lymph nodes in regards to T cells?
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What is the purpose of high endothelial venules (HEVs) in lymph nodes?
What is the purpose of high endothelial venules (HEVs) in lymph nodes?
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What is the primary function of the spleen?
What is the primary function of the spleen?
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What is the characteristic of FDCs that distinguishes them from macrophages?
What is the characteristic of FDCs that distinguishes them from macrophages?
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What is the site of lymphocyte recirculation?
What is the site of lymphocyte recirculation?
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What is the function of macrophages in lymph nodes?
What is the function of macrophages in lymph nodes?
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What is the primary function of dendritic cells?
What is the primary function of dendritic cells?
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Where are dendritic cells primarily located?
Where are dendritic cells primarily located?
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What is the role of the C-C chemokine receptor 7 (CCR7) in dendritic cells?
What is the role of the C-C chemokine receptor 7 (CCR7) in dendritic cells?
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What is the difference between dendritic cells and macrophages in terms of their interaction with T cells?
What is the difference between dendritic cells and macrophages in terms of their interaction with T cells?
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What is the function of MHC proteins in dendritic cells?
What is the function of MHC proteins in dendritic cells?
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Where do dendritic cells typically present antigens to T cells?
Where do dendritic cells typically present antigens to T cells?
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What is unique about dendritic cells compared to other antigen-presenting cells?
What is unique about dendritic cells compared to other antigen-presenting cells?
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What type of cells are found in the bone marrow?
What type of cells are found in the bone marrow?
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Study Notes
Structure of a Lymph Node
- Lymphocytes enter lymph nodes through afferent lymphatic vessels and high endothelial venules (HEVs) in the deep cortex.
- Lymphocytes move to the T and B domains of the lymph node, or pass through the parenchyma and leave via an efferent lymphatic vessel.
- The direction of lymph flow in a lymph node is: afferent lymph vessel → subcapsular sinus → intermediate (radial or trabecular) sinuses → medullary sinuses → efferent lymph vessel.
Lymph Node Function
- Lymph nodes produce and maintain T and B cells, and store memory cells (especially Th cells).
- They accumulate antigens delivered to lymph nodes to be recognized by T cells, inside and at the surface of APCs, thus initiating an immune response.
- Lymph nodes filter lymph, phagocytose lymph components, and are a site for lymphocyte recirculation.
Dendritic Cells
- Dendritic cells (DCs) are primarily located in barrier tissues, including skin and the mucosa of the gastrointestinal, respiratory, and genitourinary tracts.
- DCs collect antigens and migrate from barrier locations to local lymph nodes, where they present antigens to "naïve" T cells in the T-cell zone.
- DCs are responsible for priming naïve T cells to become activated during the initiation of an adaptive immune response.
Thymus
- The thymus is a primary lymphatic and endocrine organ responsible for T cell development.
- It is made of many pseudolobules, each with an outer cortex and an inner medulla.
- The outer cortex contains many immature T cells, which undergo selection or "education" of lymphocytes.
Follicular Dendritic Cells (FDCs)
- FDCs are found in germinal centers and have multiple, thin, hair-like branching cytoplasmic processes that interdigitate between B cells.
- Antigen–antibody complexes adhere to the dendritic cytoplasmic processes by means of the antibody’s Fc receptors, allowing FDCs to retain antigen on their surface for weeks, months, or years.
Spleen
- The spleen is a large, dark-red, oval, highly vascular lymphatic organ located to the left of the stomach below the diaphragm.
- It is organized into areas of red pulp and white pulp.
- The marginal zone of the spleen is a sinusoidal region between the red and white pulp, rich in macrophages and other APCs.
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