It is held in place by extensions of the visceral peritoneum, a very thin membrane which surrounds the spleen. The hilus, a groove which runs across the visceral surface of the spleen, serves as an exit and entry point for the splenic vein, artery, and lymphatic vessels. Inside, the spleen contains many functionally and structurally different elements.
Reticuloendothelial cells form a network of reticular fibers which constitute the pulp cords.
The membranes of these cells are coated with proteins to optimize their ability to phagocytose red blood cells. The venous sinuses are closely associated with the reticular fibers of the pulp cords. The cord and sinuses filter blood and direct it to the splenic vein, for transport out of the organ. The splenic artery and its arterioles are surrounded by a sheath of lymphatic tissue known as white pulp. The white pulp consists of lymphocytes associated with reticular cells, and can form small nodules of tissue.