Spleen

The spleen is a lymphatic organ interposed in the blood stream. The surface projection of the longitudinal axis of the spleen is the tenth rib. It is concealed anteriorly by the greater curvature of the stomach and the left colic (splenic) flexure. Its weight varies from 50 to 250g.

The spleen consists of a diaphragmatic and visceral surface.

faces upward, backward and to the left. The diaphragm separates the spleen from the 9th, 10th and 11th ribs.

gastric - greater curvature of stomach
renal - faces medially and caudally. Related to upper ventral surface of left kidney.
colic - left (splenic) flexure

directed toward the vertebral column

rests on the left colic flexure and phrenicocolic ligament

Associated ligaments of the spleen (double layers of peritoneum:

phrenicocolic ligament
gastrolienal ligament
lienorenal ligament

Functions

There are three major functions of the spleen and these are handled by three different tissues within the spleen.

Reticuloendothelial tissue - concerned with phagocytosis of erythrocytes and cell debris from the blood stream. This same tissue may produce foci of haemopoiesis when RBC's are needed.
Venous sinusoids along with the power of the spleen to contract, provides a method for expelling the contained blood to meet increased circulatory demands in certain animals.
White pulp provides lymphocytes and a source of plasma cells and hence antibodies for the cellular and humoral specific immune defenses.

Clinical Considerations

Surgical removal of the spleen may be carried out in healthy patients whose spleen has been ruptured by trauma. In the long run, splenectomy has no dire effects
There is an increased risk of infection after splenectomy, especially in very young children.
In hypertrophic spleen due to overactivity of its macrophage system, it can be removed without apparent ill effects.