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A Human Embryo of Streeter Age Group XXI

서울대학교 의과대학
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A human embryo of age group XXI of Streeter’s developmental horizon is described. The embryo was 。b t a i n ed from the right uterine tube of a 42-year-old woman who was operated for an ectopic pregnancy in 1980. The estimated age of the embryo was 45 days, and CR length was 19mm. The embryo was ‘erially cut , and 493 sagittal sections were made in 4μm thickness. Summary descriptions and scores of eight key-organs were as follows 1. The cornea was delaminating into three layers (4 points) 2. The optic stalk had no lumen , but ependymal remnant was presen t. (5 points) 3. Distal tip of cochlea was turning down. (4 points) 4. The stalk of adeno- hypophysis was threadlike. (4 points) 5. The vomero-nasal organ was a blind sac with its small opening. (3.5 points) 6. The submandibular gland showed simpIe primary branching. (5 points) 7. The kidney had many spoon-sha~ed capsules and some S·shaped ones. (4 points) 8. Osteoblasts were forming in bng bones. (5 points) Taking all these things into consideration, the embryo was believed to fall into age group XXI. Total score was 34.5 after adding all the points above, and this also corresponded to the same age group

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