The spleen (empty of blood) (20X)

The spleen is the only lymphoid organ that is an integral part of the blood circulation and acts as a filter for the blood. Exhausted erythrocytes, bacteria and viruses are phagocytosed and destroyed by the spleen's macrophages. In addition, the spleen also acts as a reservoir for erythrocytes and thrombocytes.

Depending on the type of cells found in the pulp, the splenic pulp is divided into a white and red pulp. The terms "white pulp" and "red pulp" are derived from their distinct color appearances under the microscope, which are related to their different functions and cellular compositions. The contrasting colors of the white and red pulp thus reflect their different roles and the predominant types of cells present in each region, making the terminology both descriptive and functional.

In the white pulp, there is a large excess of lymphocytes that are gathered in follicles and PALS areas (periarterial lymphatic sheaths), while in the red pulp you find mostly erythrocytes. At the transition between red and white pulp there are marginal zones which are often poorly defined.

Reticular connective tissue form the basis of the splenic pulp: Fibroblasts (reticulum cells) and collagen fibers (reticular fibers)