The labioscrotal swellings (genital swellings or labioscrotal folds) are paired structures in the human
embryo
An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
that represent the final stage of development of the
caudal end of the external
genitals
A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...
before
sexual differentiation
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. Sex determination is often distinct from sex differentiation; sex determination is the designation for the deve ...
. In both males and females, the two swellings merge:
* In the ''female'', they become the
posterior labial commissure
The labia majora (singular: ''labium majus'') are two prominent longitudinal cutaneous folds that extend downward and backward from the mons pubis to the perineum. Together with the labia minora they form the labia of the vulva.
The labia majo ...
. The sides of the
genital tubercle
A genital tubercle or phallic tubercle is a body of tissue present in the development of the reproductive system. It forms in the ventral, caudal region of mammalian embryos of both sexes, and eventually develops into a primordial phallus. In t ...
grow backward as the genital swellings, which ultimately form the
labia majora
The labia majora (singular: ''labium majus'') are two prominent longitudinal cutaneous folds that extend downward and backward from the mons pubis to the perineum. Together with the labia minora they form the labia of the vulva.
The labia majo ...
; the tubercle itself becomes the
mons pubis
In human anatomy, and in mammals in general, the ''mons pubis'' or pubic mound (also known simply as the mons, and known specifically in females as the ''mons Venus'' or ''mons veneris'') is a rounded mass of fatty tissue found over the pubic sym ...
. In contrast, the
labia minora
The labia minora (Latin for 'smaller lips', singular: ''labium minus'', 'smaller lip'), also known as the inner labia, inner lips, vaginal lips or nymphae are two flaps of skin on either side of the human vaginal opening in the vulva, situated be ...
are formed by the
urogenital folds
The development of the reproductive system is the part of embryonic growth that results in the sex organs and contributes to sexual differentiation. Due to its large overlap with development of the urinary system, the two systems are typically ...
.
HSC - Gonad Descent and Development of External Genitalia II
/ref>
* In the ''male'', they become the scrotum
The scrotum or scrotal sac is an anatomical male reproductive structure located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum cont ...
.
References
External links
"Development of Male External Genitalia", at mcgill.ca
Diagram at mhhe.com
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{{Authority control
Embryology of urogenital system
Scrotum