Lymphoid Organs Histology Class Mind Map PDF

primary site for hematopoiesis (formation of...

primary site for hematopoiesis (formation of blood cells), including lymphocytes **Bone Marrow** stem cells give rise to all blood cells, including B-lymphocytes (B-cells) that stay in the marrow to mature. **Primary Lymphoid Organs** (producing and T-lymphocytes (T-cells) produced in the bone maturing lymphocytes) marrow travel to the thymus to mature Divided into a cortex (where immature T-cells proliferate) and a medulla (where more mature T-cells reside) **Thymus** **Structure** Hassall’s corpuscles, found in the medulla, are unique structures made of concentric layers of epithelial cells that support T-cell development Cytoreticulum formation Small inactive lymphocyte accumulation **Primary Nodules** **Thymic Epithelial Cells** Desmosome junctions Cluster of lymphocytes with no germinal center (inactive) meaning it hasn’t been exposed to an antigen that triggers an immune response. Lymphoid tissue can exist in a nodular (follicular) form, containing specialized **Nodular/Follicular Lymphoid Endodermal origin When lymphocytes in a primary nodule encounter an antigen, they proliferate and form a structures called lymphatic follicles Tissue** germinal center The outer layer where lymphatic follicles are **Secondary Nodules** Cortex (contains follicles) Sous-sujet 1 located. The cortex contains both primary and Germinal Center: This is where B-cells rapidly proliferate, differentiate, and undergo processes **Lymphoid Organs** secondary nodules is a capsule, which is a dense layer of like somatic hypermutation to produce highly specific antibodies **2 Regions** connective tissue surrounding it Lymphoid Organs Medulla (contains medullary cords) The inner region with medullary cords and sinuses where lymph flows and is filtered. Does not contain the fibrous reticular tissue typically found in lymphoid organs. Instead, Histology Class Mind **Lymph Nodes** Capsule structure it relies on a cytoskeletal structure called the cytoreticulum, formed by thymic epithelial cells (originating from the endoderm). These cells are joined by desmosomes **Thymus** Map B and T-cell activation —protein complexes that connect cells tightly together **Without Reticular Tissue** **Bursa of Fabricius** (in birds) Positioned in the pharyngeal region, tonsils protect against pathogens entering the body **Lymphoid Structures** via the mouth or nose **Lymph Nodes** **Tonsils** They are strategically located to provide early immune responses to inhaled or ingested materials **Spleen (Splenic Pulp)** These organs contain reticular fibers made **With Reticular Tissue** from collagen that form a network contain lymphatic follicles within a specialized epithelial covering **Tonsils** **Secondary Lymphoid Organs** (sites where lymphocytes encounter antigens (foreign Filters blood, not lymph **MALT** molecules) and initiate immune responses) **Spleen** Contains lymphocytes and is involved in White Pulp (lymphocytes) immune responses to blood-borne antigens encapsulated and divided into two main areas: **Regions** Contains splenic cords and sinusoids where Red Pulp (splenic cords, removes old RBCs) old or damaged red blood cells are filtered and removed from the blood Immune response at mucosal surfaces found in regions exposed to the external environment, such as the gastrointestinal tract (GALT) and respiratory tract (BALT) **MALT (Mucosa-Associated Lymphoid Tissue)** In MALT, clusters of immune cells are located within the connective tissue layers of mucous membranes. This arrangement allows MALT to protect areas of the body that are often exposed to germs, such the respiratory tract **No connective tissue capsule**