A Human Embryo of Streeter Age Group XVI

Abstract

A human embryo obtained incidentally from a hysterectomized uterus was examined. A total of 204 sections of slides was made and observed microscopically to determine the age of the embryo. The upper and lower limb buds were recognizable but digital rays were absent. The embryo showed early differentiation of semilunar valves, aorticopulmonary septum, renal pelvis forming upper and lower poles and appearance of pigment granules in the outer coat of retina. There was no vermiform appendix, and the dorsal and ventral pancreata had not yet fused. Any abnormality was not recognizable. From the above findings, we concluded that this embryo belonged to the age group XVI of Streeter's developmental horizon.