A scanning electron microscopy study of human spleen: relationship between the microcirculation and functions.

This paper reviews scanning electron microscope (SEM) observation of the circulatory system of the human spleen, based on our findings on freeze-cracked surfaces and vascular casts of the spleen. Central arteries ran straight in the white pulp without branching out follicular arteries and became penicillar arteries in the red pulp. Some penicillar arteries returned to the marginal zone. Some of their branches ended by opening there, whereas others passed through the marginal zone, entered the white pulp and became follicular arteries. Some of them took the shape of an "arteriolar-capillary bundle". Most of the follicular capillaries ended opening into the marginal zone. The penicillar arteries usually ran straight or gently curved among the sinuses of the red pulp and opened into cordal spaces. Occasional arteries formed a labyrinthine structure of arterial channels which directly connected with thin sinuses. This study reveals that three different modes of arterial terminals are available in the human spleen: arterial openings in the marginal zone which seem significant for presentation of antigens to the white pulp, openings into the cords of Billroth which facilitate culling and pitting of blood cells, and direct connections with sinuses (closed circulation) which account for the physiologically known quick blood flow through the spleen.