A Human Embryo of Streeter Age Group XV
نویسندگان
چکیده
= Abstract =A human embryo considered to belong to stage XV of Streeter's developmental horizon is presented. The embryo was obtained surgically from tubal pregnancy. The crownrump(CR) length was 8.5 rom. A total of 600 serial sections were made through the frontal plane and the following distinguishing features of the key organs were found. There was closure of the lens vesicle, evagination of the endolymphatic duct, overgrowth of the second branchial arch, well formed endocardial cushions, secondary bronchial subdivisions, ureteric bud inducing early metanephric blastema, and the appearance of ventral pancreatic bud. Beginning of pigmentation in the outer layer of the retina was the only finding that did not strictly meet the criteria of stage Xv. Authors classified the embryo in the late age group XV of Streeter's developmental horizon.
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