following are the components of the white pulp of spleen

016. All of the following are the components of the white pulp of spleen, except :

1. Periarteriolar lymphoid sheath.

2. B cells.

3. Antigen presenting cells.

4. Vascular sinus.

Answer

4. Vascular sinus.

Reference:

Guyton 11^th Edition Page 434

Gray 38^th Edition Page 1439

Robbins 7^th Edition Page 702

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Discussion

The spleen is also covered externally by a series of connective tissue bars (trabeculae); they ramify throughout the whole structure to create a fibrous skeleton supporting its delicate tissues, which include both lymphoid tissues (white pulp) and extensive areas of blood-filled tissue (red pulp). In the living the spleen is soft and friable, and is dark purple because of the considerable amount of blood within its substance.

Explanation

Microscopically, the internal mass (parenchyma) of the spleen consists of two major components, known as white pulp and red pulp, denoting their appearance when the freshly excised spleen is transected. The white pulp is composed of lymphoid tissue in which B and T lymphocytes can mature and proliferate under antigenic stimulation. The red pulp is a unique filtration device which enables macrophages in the spleen to extract particulates from the blood as it perfuses this organ. Red pulp is composed of a complex system of interconnected spaces inhabited by large numbers of phagocytic macrophages. These cells remove and dismantle effete red blood cells, micro-organisms, cellular debris and other particulates from the circulation. At the junction of white and red pulp is a narrow marginal zone, an area important in establishing immune responses and other aspects of splenic biology.

Comments

The red pulp constitutes the majority (about 75%) of the total splenic volume. Within it lie large numbers of venous sinuses draining into tributaries of the major splenic veins.

Tips

The sinuses are separated from each other by a fibrocellular network, the reticulum, formed by numerous fibroblasts (reticular cells) and small bundles of delicate collagen fibres, in the meshes of which lie splenic macrophages. Seen in two-dimensional sections, these intersinusal regions appear as strips of tissue, splenic cords (of Billroth), alternating with splenic sinuses although in reality they form a three-dimensional continuum around the venous spaces. To understand the organization of the red pulp some details of the sinuses and of the intersinusal reticulum are required, as follows.