Subcapsular sinuses are seen in -
Ans. is 'd' i.e., Lymph node o When a section through a lymph node is examined, it is seen that it has an outer darker zone called cortex and a lighter inner zone called medulla.o Within the cortex are several rounded areas that are called lymphoid follicles and each nodule has a paler staining germinal centre surrounded by a zone of densely packed lymphocytes,o The lymph node is surrounded by a capsule and a number of septae extend into the node from the capsule and divide it into lobules.o Afferent lymphatics reaching the convex outer surface of the node enter an extensive subcapsular sinus. From this sinus, a number of radial cortical sinuses run through the cortex towards the medulla. Reaching the medulla, the sinuses join to form larger medullary' sinuses. In turn, the medullary' sinuses join to form one efferent vessel through which lymph leaves the node.Special histological features about other options:SPLEEN:White pulp of the spleen is formed of a mass of T and B lymphoctytes arranged as lymphoid nodules. Each nodule has an eccentrically placed central arteriole. Blood passes outwards from the central arteriole to reach the marginal zone surrounding the white pulp. The nodules are also called Malpigian bodies.The red pulp is made up of a mesh of leaky sinusoids! vascular sinuses) through which the red cells are squeezed. Cells lining the sinusoids are phagocytic. So the red pulp surrounds the lymphoid follicles (white pulp). The part of the red pulp immediately surrounding the white pulp is called the marginal zone. The marginal zone contains antigen presenting cells.THYMUS:1. Hassall's corpuscles found in the medulla are highly specific.THYROID:1. The gland is covered by a fibrous capsule, septae from which divide it into lobules.Each lobule is made up of an aggretation of follicles, lined by follicular cells. The follicle has a cavity filled with a homogenous material called colloid.Apart from the follicular cells, the thyroid gland contains C-cells or parafollicular cells which intervene between the follicular cells and the basement membrane.Lymph nodeso Lymph nodes are placed along the course of lymphatic vessels.o They are surrounded by a fibrous capsule from which trabeculae penetrate into the nodes,o There are two zones in lymph nodesOuter cortexInner medullao Subcapsular sinus lies immediately deep to the capsule and immediately above the cortex, i.e. between the capsule and cortex.Cortexo In cortex, there is accumulation of proliferating lymphocytes to form follicle (primary follicle),o Beside proliferating lymphocytes, cortical follicle also contains dendritic macrophages,o On antigenic stimulation, germinal centers (secondary follicles) develop writhin the primary follicles.Medullao The lymphocytes,plasma cells and macrophages are arranged as donated branching bands; i.e. Medullary Cords.o Cortical follicles and medullary cords contain B-lymphocytes.o Between the corticle follicle and medullary cords, there is paracortical area which contains T-lymphocytes.
Spleen
Thymus
Thyroid
Lymphnode
Histology