Lymphoid II Flashcards
Central lymphoid organs
Thymus and bone marrow
Peripheral lymphoid organs
Lymph nodes and spleen (encapsulated), and MALT (unencapsulated). There function is antigen surveillance (the immune system is looking for foreign antigens).
PALS
Periarterial lymphatic sheath that wraps around the central artery in the spleen. Location of T cells
Circulating lymphocytes
75% T cell, 10% B cell, 15% Natural killer cell
Diffuse lymphoid tissue
Tissue located in the lamina propria that contains B lymphocytes, eosinophils and plasma cells that secrete IgA
MALT
Mucosal associated lymphatic tissue. Located within unencapsulated peripheral organs and contains most lymphatic tissue.
IgA
Secretory immunoglobulin that protects most mucosal epithelium. It is differentiated from plasma cells and contains a secretory component that protects it from degradation of lysosomes as it is released into the lumen.
Solidary nodules
Diffuse and naive B lymphocytes that have aggregated into nodules (follicles). They are unencapsulated and have no connective tissue around the outer layer.
Aggregated nodules
They are partially encapsulated nodules. They are located in the tonsils, Peyers patches, and vermiform appendix.
Peyer’s patches
Aggregated nodules that form in the ileum of the GI tract from loose lymphatic tissue. They aggregate to from primary nodules.
Secondary nodules
Activated nodules that are identified by a germinal center and a dense uniform mantle around the outside. The germinal center contains more cytoplasm (plasma cells making immunoglobulins).
Primary nodules
Nodules that have not been activated and are completely dense and uniform (no germinal center, cytoplasm)
Microfold cells
Cells in Peyer’s patches that directly bind pathogens and then pass it to a macrophage to activate an immune response by B and T lymphocytes.
Vermiform appendix
Aggregated nodule that forms the terminal narrowed point of the cecum.
McBurney’s point
Point of vermiform appendix that indicates position of the appendix.
Thymus
Fully encapsulated central organ that produces thymocytes for antigen surveillance. 95% of self antigen T cells are phagocytized while only 5% of the non-self T cells are released into circulatory system for antigen surveillance. Maturation of the thymocytes occurs in the cortex.
Blood-thymus barrier
Prevents formed elements of the blood from coming into contact with thymocytes in the cortex of the lobules. This is an area where you don’t want an immune response to occur.
Hassal’s corpuscles
Bundles of epithelial reticular cells in the medulla of the thymus. Distinguishing feature of the thymus that defines it as a component of the immune system. Secretes cytokines.
Lymph nodes
Encapsulated node that acts as a filter of the lymphatic fluid and drains the lymphatic tissue back to venous vessels. Contains B cells in cortical nodes and T cells in the paracortex.
- They are also biopsy points for tumor cells.
Postcapillary high endothelial venules (HEV)
Venules that get blood to the lymph nodes. They are cuboidal endothelium and located in the paracortex
Spleen
Encapsulated organ that acts as a filter of the blood that also plays a role in the immune response.
- Storage of platelets for a blood clot response
- hematopoiesis outside of the bone marrow.
White pulp
Leukocyte component of the spleen.
- Nucleated
- Most of the cells are B lymphocytes
Red pulp
Erythrocyte component of the spleen. Non-nucleated
Periarterial lymphatic sheath
Sheath that wraps around the central artery in the spleen. It contains T cells.
Open sinusoids
90% of blood filtration occurs here. They contain slits that allow erythrocytes travel from the sinusoid to the red pulp. Only healthy erythrocytes can squeeze back though the slits in the open sinusoids. The rest are destroyed by macrophages.
Germinal center
Responsible for activating the immune cells in the secondary nodule. It contains more cytoplasm for plasma cells to make immunoglobulins
