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Terms in this set (22)
What are characteristics of lymph?
Fluid that is collected from the tissues and returned to systematic circulation. Lack large molecules.
What is primary lymphoid tissue?
Location of lymphocyte production and differentiation. Bone marrow and thymus.
What is secondary lymphoid tissue?
Location of lymphocyte-antigen interaction. Diffuse tissue is found under epithelial surfaces. Lymph nodes respond to lymph-borne antigens. Spleen responds to blood-borne antigens.
What is BALT?
Bronchus-associated lymphatic tissue is a respiratory specific type of diffuse tissue.
What is MALT?
Mucosal-associated lymphatic tissue is diffuse tissue found in the tonsils and gut.
What are nodules?
Dense collections of lymphocytes.
What are follicles?
Dynamic collections of B cells.
What is a primary follicle?
Accumulation of B cells due to Ab-driven proliferation. Cells are no long proliferating. Appears as a homogeneous dark circle of cells.
What is a secondary follicle?
Location of active Ab-driven proliferation of B cells. Germinal center is a light colored, mitotically active group of cells.
Describe the histological organization of a lymph node.
What is the composition of lymphocytes in lymph nodes and where are they found?
70% T cells and 30% B cells. B cells are found in the cortex and activated cells will appear as follicles. T cells are found in the paracortex (just above the medulla) and is the location of interaction between T cells, B cells and antigen.
How does lymph flow through a lymph node?
Lymph entes an LN through afferent vessels and flows into the subcapsular lymphatic sinus that lies deep to the capsule and surrounds the cortex. Lymph then flows through cortex and paracortex to enter the medulla and eventually exit through efferent vessels.
What cells are found in the lymph node medulla?
T cells, B cells, plasma cells and macrophages.
How do lymphocytes enter lymph nodes?
Lymphocytes exit systematic circulation by crossing the walls of post-capillary venues in the medulla.
What is immune surveillance?
Movement of lymphocytes through the circulatory system: blood to LNs to lymph to blood.
What is the composition of lymphocytes in the spleen?
70% B cells and 30% T cells (opposite of LNs).
What are the functions of the spleen?
1. Immune: response to blood-borne antigens in the WHITE PULP.
2. Blood filtration: metabolism of old RBCs in the RED PULP.
Describe the histological organization of the spleen.
Mesencymal stromal cells produce reticular fibers (type III collagen). Lymphocytes enter the white pulp via marginal venus sinuses.
How do lymphocytes develop and mature?
What are the embryological origins of the thymus?
Derived from third pharyngeal pouch endoderm, with contributions from neural crest cells.
Describe the histological organization of the thymus?
Lobulated outer cortex more darkly stained. No lymphatic or venous sinusoids. Central medulla contains less thymocytes and is stained more lightly. Whorls of medullary epithelial cells (eosinophilic) called Hassall's bodies, are unique to the thymus.
What is the function of the thymus?
Location of T cell maturation. Not a location of antigen exposure and immune response.
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