Paracortex of lymph node between cortical follicles and medulla contains:
Correct Answer: All of the above
Description: Ans. D. All of the above > A. Proliferating T cells.Lymph Nodes: Lymph nodes are located at sites throughout the body, strategically placed to process antigens present in lymph drained from most organs via the afferent lymphatics. Lymph nodes have a capsule, a cortex, a medulla, and sinuses (subcapsular, cortical, and medullary) The sinuses contain macrophages that take up and process antigen, which may then be presented to lymphocytes. The cortex is divided into follicular and diffuse (paracortical) regions, and the medulla into medullary cords and sinuses. The paracortex contains high endothelial venules (HEV) (through which both T and B lymphocytes enter the node) and specialized antigen-presenting cells (APCs), the interdigitating dendritic cell, and which may be related to the cutaneous Langerhans cell, and which present antigen to cells. Both T cell and early B cell reactions to antigen occur in the paracortex, while the germinal center (GC) reaction occurs in the follicular cortex. The follicular cortex also contains a specific type of accessory cell, the follicular dendritic cell (FDC); adhesion to the FDC- antigen complex is important in the differentiation of B cells in response to antigen. Plasma cells and effector T cells generated by immune reactions accumulate in the medullary cords and exit via the medullary sinuses.Lymphnode is a 2deg lymphoid organ that has many afferents, 1 or more efferents. Encapsulated, with trabeculae. Functions are nonspecific filtration by macrophages, storage of B and T cells, and immune response activation. The hmph node is associated with afferent and efferent lymphatic vessels. It is surrounded by a capsule, has trabeculae, and can be divided into outer cortical, inner cortical (paracortical), and medullary regions. FollicleSite of B-cell localization and proliferation. In outer cortex. 1deg follicles are dense and dormant. 2deg follicles have pale central germinal centers and are active.MedullaConsists of medullary cords (closely packed lymphocytes and plasma cells) and medullary sinuses.Medullary sinuses communicate with efferent lymphatics and contain reticular cells and macrophages.ParacortexHouses T cells. Region of cortex between follicles and medulla. Contains high endothelial venules through which T and B cells enter from blood. Not well developed in patients with DiGeorge syndrome. Paracortex enlarges in an extreme cellular immune response (e.g., viral infection).Structure of Lymph node
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