사람태아의 비장 발육에 관한 형태학적 연구

Abstract

The spleens of human fetuses aged from 5 to 40 weeks were studied light and electron microscopically to investigate the development of the white pulp and the erythropoietic activities. The splenic primodium was first seen at the 5th week as a dense mass of mesenchymal cells on the left side of the dorsal mesogastrium. At the 9th week the spleen acquired it's characteristic form, and became progressively converted into loose. spongy reticular meshwork. At the 13th week there appeared many developing vessels and wide blood sinuses in the reticulum, and a number of erythrocytes and erythroblasts were present in or out of vessels. No significant level of erythropoiesis was observed until the 12th week although a few of erythroblasts were present in the capillaries of the splenic primodium. At the 13th week many mitotic ligures of erythroid cells were recognized, and the erythropoiesis continued until the end of gestation, being especially active during the middle third of fetal development. The differentiation of the white pulp has begun at the 13th week as the periarterial lymphatic sheath, which consisted of circumferentially arranged reticular cells and fibers around the central artery and loaded with large and medium sized lymphocytes, rnacrophages and a few erythrocytes. With advancing age, the white pulp increased in its size, and periarterial lymphatic sheath packed with small lymphocytes more predominantly. The primary follicle in the white pulp appeared first at the 21th week, but no germinal center was observed throughout gestation.