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Questions and Answers

What is the primary function of high endothelial venules (HEVs) in lymph nodes?

  • To store lymphocytes for future immune responses
  • To filter out pathogens from the lymph
  • To facilitate the entry of lymphocytes into the lymph node (correct)
  • To produce antibodies against invading pathogens
  • What is the order of lymph flow through a lymph node?

  • Afferent lymph vessel -> Intermediate sinuses -> Medullary sinuses -> Subcapsular sinus -> Efferent lymph vessel
  • Afferent lymph vessel -> Subcapsular sinus -> Intermediate sinuses -> Medullary sinuses -> Efferent lymph vessel (correct)
  • Afferent lymph vessel -> Medullary sinuses -> Intermediate sinuses -> Subcapsular sinus -> Efferent lymph vessel
  • Afferent lymph vessel -> Medullary sinuses -> Subcapsular sinus -> Efferent lymph vessel
  • What is the purpose of the paracortex in a lymph node?

  • To provide a site for antigen presentation and T cell activation (correct)
  • To filter out pathogens from the lymph
  • To facilitate the entry of lymphocytes into the lymph node
  • To store lymphocytes for future immune responses
  • What is the ultimate destination of lymphocytes that enter the lymph node?

    <p>The right lymphatic trunk and then the systemic circulation</p> Signup and view all the answers

    What is the function of the reticular fibers in the stroma of the lymph node?

    <p>To provide structural support to the lymph node</p> Signup and view all the answers

    What is the region between the cortex and medulla of a lymph node called?

    <p>Paracortex or inner/deep cortex</p> Signup and view all the answers

    What is the purpose of the afferent lymphatic vessels in relation to lymph nodes?

    <p>To transport lymphocytes into the lymph node</p> Signup and view all the answers

    What is the site where lymphocytes enter the lymph node through the wall of high endothelial venules (HEVs)?

    <p>Cortex</p> Signup and view all the answers

    What is the primary function of the lymphoid nodule/follicle?

    <p>To facilitate the proliferation and differentiation of lymphocytes</p> Signup and view all the answers

    What type of cells can be found in the germinal center of a lymphoid nodule/follicle?

    <p>Antigen-presenting macrophages and proliferating B lymphocytes</p> Signup and view all the answers

    What is the function of the marginal zone in a lymphoid nodule/follicle?

    <p>To store newly formed adult B cells and some T cells</p> Signup and view all the answers

    What cell type is responsible for 'education' of lymphocytes in the thymus?

    <p>Thymic epithelial cells</p> Signup and view all the answers

    What is the composition of the cortical region of the thymus?

    <p>Many immature T cells and some macrophages</p> Signup and view all the answers

    What structure separates the lobules of the thymus?

    <p>Connective tissue septa</p> Signup and view all the answers

    What is the primary function of the thymus?

    <p>To facilitate the development of T cells</p> Signup and view all the answers

    What type of cells can be found in the medulla of the thymus?

    <p>Not specified in the text</p> Signup and view all the answers

    What is the function of the strands of basal lamina in the splenic sinus?

    <p>To loop around the outside of the sinus</p> Signup and view all the answers

    What type of cells are found in the marginal zone of the spleen?

    <p>Macrophages, dendritic cells, and B lymphocytes</p> Signup and view all the answers

    What is the location of the marginal zone in the spleen?

    <p>Between the red and white pulp</p> Signup and view all the answers

    What is unique about the wall of the splenic sinuses?

    <p>It lacks a continuous basal lamina</p> Signup and view all the answers

    What is the source of blood in the marginal zone?

    <p>Central artery</p> Signup and view all the answers

    What happens to circulating T and B lymphocytes when they enter the spleen?

    <p>They enter the marginal zone before segregating to specific locations</p> Signup and view all the answers

    What is the primary function of FDCs in germinal centers?

    <p>Retention of antigen on the surface for prolonged periods</p> Signup and view all the answers

    What is the origin of FDCs?

    <p>Lymphoid</p> Signup and view all the answers

    What is the function of lymph nodes in regards to T cells?

    <p>Storage of memory T cells</p> Signup and view all the answers

    What is the purpose of high endothelial venules (HEVs) in lymph nodes?

    <p>Recirculation of lymphocytes</p> Signup and view all the answers

    What is the primary function of the spleen?

    <p>Filtration of blood</p> Signup and view all the answers

    What is the characteristic of FDCs that distinguishes them from macrophages?

    <p>Lack of MHC II molecules</p> Signup and view all the answers

    What is the site of lymphocyte recirculation?

    <p>Blood-lymph node-lymph-blood</p> Signup and view all the answers

    What is the function of macrophages in lymph nodes?

    <p>Phagocytosis of lymph components</p> Signup and view all the answers

    What is the primary function of dendritic cells?

    <p>To present antigens to T cells and initiate an immune response</p> Signup and view all the answers

    Where are dendritic cells primarily located?

    <p>In barrier tissues, including skin and mucosa</p> Signup and view all the answers

    What is the role of the C-C chemokine receptor 7 (CCR7) in dendritic cells?

    <p>To sense and migrate towards chemokines in the lymphoid tissue</p> Signup and view all the answers

    What is the difference between dendritic cells and macrophages in terms of their interaction with T cells?

    <p>Dendritic cells interact with naïve T cells, while macrophages interact with already-activated T cells</p> Signup and view all the answers

    What is the function of MHC proteins in dendritic cells?

    <p>To present antigens to T cells</p> Signup and view all the answers

    Where do dendritic cells typically present antigens to T cells?

    <p>In the lymph node</p> Signup and view all the answers

    What is unique about dendritic cells compared to other antigen-presenting cells?

    <p>They can present virtually any form of protein antigen on both MHC I and MHC II</p> Signup and view all the answers

    What type of cells are found in the bone marrow?

    <p>T cells, B cells, and NK cells</p> Signup and view all the answers

    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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