Open microcirculation of the spleen is related to its function as a blood filter

Abstract

Microcirculation of the spleen is highly characteristic and open in the human and rat spleen. The open microcircultaion system in the spleen is closely related to its function. Blood enters the spleen by way of the splenic artery that passes through the splenic hilus. The splenic artery branches into trabeculae as the trabecular artery, which turns out of the trabeculae and enters the white pulp. The arteries are surrounded by periarteriolar lymphatic sheaths (central artery). The central artery sends out branches, which terminate in the marginal zone. In the rat spleen, the marginal sinus, formed by the arterial terminal, envelopes the white pulp and bounds the inner edge of the marginal zone. The central artery itself runs out into the red pulp, called the penicillar artery, and terminates in the cords. Blood flows out of the arterial terminal in the marginal zone and the splenic cords. The hemodynamic condition varies in the marginal zone and the splenic cords. Intraarterial injection of two different sized particles into the rat spleen revealed that large particles appeared mainly in the splenic cords and small particles mostly in the marginal zone. The results suggest that blood cells flow out mainly from the penicillar arteries into the splenic cord. Blood-born antigens are trapped in the marginal zone, which functions as an immunological filter.