A genital tubercle, phallic tubercle, or clitorophallic structure is a body of tissue present in the
development of the reproductive system of
amniote
Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...
s. It forms in the ventral, caudal region of
mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
ian
embryos of both
sexes, and eventually develops into a
primordial phallus. In the human
fetus
A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic development, embryonic stage, the fetal stage of development takes place. Pren ...
, the genital tubercle develops around week four of
gestation
Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregn ...
, and by week nine, becomes recognizably either a
clitoris
In amniotes, the clitoris ( or ; : clitorises or clitorides) is a female sex organ. In humans, it is the vulva's most erogenous zone, erogenous area and generally the primary anatomical source of female Human sexuality, sexual pleasure. Th ...
or
penis
A penis (; : penises or penes) is a sex organ through which male and hermaphrodite animals expel semen during copulation (zoology), copulation, and through which male placental mammals and marsupials also Urination, urinate.
The term ''pen ...
. This should not be confused with the
sinus tubercle which is a proliferation of
endoderm induced by paramesonephric ducts. Even after the phallus is developed (either a
penile shaft or
clitoral shaft), the term genital tubercle remains, but only as the terminal end of it,
which develops into either the
glans penis
In male human anatomy, the glans penis or penile glans, commonly referred to as the glans, (; from Latin ''glans'' meaning "acorn") is the bulbous structure at the Anatomical terms of location#Proximal and distal, distal end of the human penis ...
or the
glans clitoridis.
In the development of the male fetus, the two sides of the tubercle approach ventrally forming a hollow tube that encloses the
male urethra. The two glans wings merge in the midline forming the
septum glandis. In the female fetus, the tubercle is attached to the vestibular folds that remain unfused forming the
labia minora and the
vaginal vestibule in between.
The genital tubercle is sensitive to
dihydrotestosterone and rich in
5-alpha-reductase, so that the amount of fetal
testosterone
Testosterone is the primary male sex hormone and androgen in Male, males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testicles and prostate, as well as promoting se ...
present after the second month is a major determinant of phallus size at birth.
See also
*
Clitorophallus
*
Sexual differentiation
References
External links
*
Overview at mcgill.ca
{{DEFAULTSORT:Genital Tubercle
Embryology of urogenital system