The spleen is formed by reticular and lymphatic tissue and is the largest lymph organ. The spleen lies in the left hypochondriac region of the abdominal cavity between the fundus of the stomach and the diaphragm. It is purplish in colour and varies in size in different individuals, but it is usually about 120mm (4.75 inches) long, 70mm wide (2.75 inches) and 25 mm (1 inch) thick. It weighs about 0.2 Kg (just under half a pound).

Structure: The spleen is slightly oval in shape with the hilum on the lower medial border. The anterior surface is covered with peritoneum. It is enclosed in a fibroelastic capsule that dips into the organ, forming trabeculae. The cellular material, consisting of lymphocytes and macrophages, is called splenic pulp, and it lies between the trabeculae. Red pulp is the part suffused with blood and white pulp consists of areas of lymphatic tissue where there are sleeves of lymphocytes and macrophages around blood vessels.

The picture on the left shows the position of the spleen on the left side of the body