21.5 The external genitalia

• Indifferent stage
• Differentiated stage of the male genitalia
• Differentiated stage of the female genitalia

Differentiated stage of the female genitalia

The mechanisms that are responsible for the development of the external female genitalia are still not well understood. It is known, though, that the placenta produces estrogen and the ovaries also appear to contribute some.

The genital tubercle lengthens only a little, retracts again and, after 14 weeks, the clitoris is recognizable.
The genital swellings do not fuse and, for this reason, the urgenital sinus remains wide open with the urethra in the anterior part and the vagina in the posterior part (vaginal vestibule).

The urethral folds also do not fuse. Out of them arise the labia minora.
From the genital swellings arise the labia majora. They fuse only in the rear portion and form the posterior commissure of the labia. In the front they form the mons pubis.

Towards the rear, the posterior labial commissure is continued by the perineum.

Fig. 62
In the female, the genital tubercle lengthens only a little and shrinks again while forming the clitoris. The urethral folds do not fuse and the urogenital sinus remains wide open.

Fig. 63, Fig. 64
The urehtral folds do not fuse – the labia minora arise from them. From the genital swellings arise the labia majora. They fuse only in the rear part and form the posterior labial commissure that is continued towards the rear by the perineum.