21.5 The external 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).

Reminder

Diagrams of indifferent stages


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 - Differentiated female genitalia
ca. 10th week
 Legenda

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 - Differentiated female genitalia
ca. 12th week
Fig. 64 - Differentiated female genitalia
fetus, from the 14th week
 Legenda

1
2
3
4
5
6
Genital tubercle
Genital swelling
Clitoris
Labia minora
Labia majora
Mons pubis


7
8
9
10
11
Perineum
Posterior labial commissure
Anus
Hymen
External urethral orifice

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.



Overview table

Overview table comparing the differentiation of the external genitalia in males and in females.
Formation of the ovaries and the external genitalia



Beginning of the chapter | Previous page | Next chapter