Histology and embryology / José F. Nonidez.

  • Nonidez, José F. (José Fernandez), 1892-1947.
Date:
1941
Catalogue details

Licence: In copyright

Credit: Histology and embryology / José F. Nonidez. Source: Wellcome Collection.

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    a. Genital tubercle. This round eminence develops in the ven- tral body wall between the umbilical cord and the tail. b. Urethral groove and folds. It is located on the caudal surface of the tubercle, and is separated from the anus by the primitive perineum. The margins of the groove are the urethral folds. c. Phallus. This is visible by the end df the 7th week as a cylin- drical prolongation ending distally as a rounded glans. d. Labio-scrotal swellings. They occur on each side of the base of the phallus, from which they are separated by a groove. 2. Transformation in the two sexes. The fate of the parts just mentioned differs according to the sex, which cannot be recog- nized for sure until the end of the 10th week. a. Male. (1) Formation of the urethra. This is accomplished through transformation of the urethral groove into a hollow tube; the fused edges of the groove constitute the raphe. (2) Migration of the scrotal swellings. These shift caudad and each becomes a half of the scrotum, separated from the other half by the raphe and the underlying scrotal septum. (3) Elongation of the penis. It is accompanied by a continua- tion of the formation of the urethra, which finally reaches the glans. (4) Corpora cavernosa. They arise as columns of mesenchyme within the shaft of the penis. b. Female. The changes are less marked and take place much more gradually. (1) Phallus. It lags in development and becomes the clitoris; its distal portion is the glans clitoridis. (2) Urethral groove. This never reaches the glans, as in the male, but remains open as the vestibule. (3) Urethral folds. They become the labia minora. (4) Labio-scrotal swellings. They grow caudad and fuse in front of the anus as the posterior commisure, while their lateral portions are converted into the labia majora. H. Anomalies. True hermaphroditism in man is very rare; false hermaphroditism, characterized by the presence of the genital glands of one sex with external genitalia and secondary sexual char- acteristics of the other, is much more frequent. When the lips of [147]