The spleen is a large dark-red ovoid organ situated on the left side of the body below and behind the stomach. The spleen is a major component of the reticuloendothelial system, producing lymphocytes in the newborn and containing phagocytes, which remove worn-out red blood cells and other foreign bodies from the bloodstream. It also acts as a reservoir for blood and, in the fetus, as a source of red blood cells.

Unit 3,

Reference: Oxford Concise Medical Dictionary (9th ed) Oxford University Press 2015 ISBN-13: 9780199687817, p2384