QS Study

The spleen is an organ in the upper far left part of the abdomen, to the left of the stomach. It is a vital organ for the maintenance of bodily fluids balanced, but it is possible to live without it. It acts as a filter for blood as part of the immune system. It also helps fight certain kinds of bacteria that cause pneumonia and meningitis.

Histological structure of spleen:

(A) Outer most covering – serous coat.

(B) Supporting Tissue –

  • Capsule: Covered by mesothelium.
  • Coarse trabeculae: Extend inwards from the capsule and hilum. They branch and anastomose and thus divide the spleen into a large number of lobules.
  • Fine reticulum: Forms the frameworks of splenic pulp.

(C) Splenic pulp –

(i) White pulp: The aggregation of T and B lymphocytes around the central arterioles forms a white pulp. Each Central arteriole is invested by a lymphatic sheath. A number of radial vessels project from the central arteriole to the periphery of white pulp where they join with the marginal sinus consisting of antigen presenting cell.

(ii) Red pulp: 75% of splenic parenchyma is formed by red pulp., which contains a large number of venous sinusoids ( draining into the tributaries of a splenic vein). Venous sinusoids are lined by endothelial stave cell which rests on a perforated basal lamina and supported externally by circularly oriented reticular fiber. The cytoplasm of this cell contains actin and myosin. The spaces between venous sinuses are filled with fibro cellular Billroth’s cords which contain a labyrinth of macrophages.

(D) Cell population

(i) B and T lymphocytes,

(ii) Blood cells,

(iii) Histiocytes.

Functions

  • Phagocytosis,
  • Haemopoiesis,
  • Immune response,
  • Storage of RBC.

Development – Iris derived from – mass of mesenchymal cells located between the layers of the dorsal mesogastrium.