To evaluate the maturing process of male gonad during intrauterine life, a morphologic study was made, based on 135 normal human fetuses ranging in age from 16 to 40 gestation weeks. These fetuses were the products of induced deliveries, and were found to have no associated diseases or congenital anomalies at autopsy.
Following observations were made:
1. Cross diameter of fetal testis increased as the fetuses approached the term. There were two structurally different periods during fetal development: One was rapid phase that lasted from 16th to 22nd week of gestation, and the other was slow phase that was from the 23rd to 40 weeks of gestational age.
2. The interstitial cells became prominent during the period of the 16th to 20th week of gestation and did rapidly disappear thereafter.
3. Mean diameter of seminiferous tubules decreased from 68.3μ at the 16th week to 55.5μ at the 24th week and to 49.0μ by term.
4. Approximate ratio of spermatogonium to total cells in seminiferous tubules were 18.7~23.9% throught the entire fetal period examined. E type spermatogonia were generally dominant component and A type spermatogonia appeared to decrease in number as the fetuses reached the term.
5. The tunica albuginea was incompletely formed and measured 40μ in thickness at the 16th week. It bacame progressively stabilized and thicked to be 210μ at the 34th week and 240μ by term.
6. The rete testis communicated with seminiferous tubules by abortive lumens at the 16th week and became completely matured by 32 weeks of age.
7. There were 5 cases of ectopic adrenal glands embeded in testis among 135 cases, thus showing an incidence of 3.7%.
8. Based on above observations it could be concluded as that first evidence of maturation as a male testis in fetal period was seen at the 24th week of gestation, thereafter it became slowly and progressively matured to show adult type histology except for spermatogenesis, by the 34th week of gestation.
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