Spleen - Function

Area Function Composition
red pulp Mechanical filtration of red blood cells. In mice: Reserve of monocytes
  • "sinuses" (or "sinusoids"), which are filled with blood
  • "splenic cords" of reticular fibers
  • "marginal zone" bordering on white pulp
white pulp Active immune response through humoral and cell-mediated pathways. Composed of nodules, called Malpighian corpuscles. These are composed of:
  • "lymphoid follicles" (or "follicles"), rich in B-lymphocytes
  • "periarteriolar lymphoid sheaths" (PALS), rich in T-lymphocytes

Other functions of the spleen are less prominent, especially in the healthy adult:

  • Production of opsonins, properdin, and tuftsin.
  • Creation of red blood cells. While the bone marrow is the primary site of hematopoiesis in the adult, the spleen has important hematopoietic functions up until the fifth month of gestation. After birth, erythropoietic functions cease, except in some hematologic disorders. As a major lymphoid organ and a central player in the reticuloendothelial system, the spleen retains the ability to produce lymphocytes and, as such, remains an hematopoietic organ.
  • Storage of red blood cells, lymphocytes and other formed elements. In horses, roughly 30% of the red blood cells are stored there. The red blood cells can be released when needed. In humans, up to a cup (236.5 ml) of red blood cells can be held in the spleen and released in cases of hypovolemia. It can store platelets in case of an emergency. Up to a quarter of lymphocytes can be stored in the spleen at any one time.
  • In mice, the spleen stores half the body's monocytes so that upon injury they can migrate to the injured tissue and transform into dendritic cells and macrophages and so assist wound healing.

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