A phallic tubercle or genital tubercle is a body of tissue present in the development of the urinary and reproductive organs

Development of the urinary and reproductive organs

The development of the urinary and reproductive organs as a part of the prenatal development, concerns the urinary system and sex organs. The latter is a part of the stages of sexual differentiation....

. It forms in the ventral, caudal region of mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

ian embryo

Embryo

An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

s of both sex

Sex

In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...

es, and eventually develops into a phallus

Phallus (embryology)

In embryology, the primordial phallus refers to the clitoris of a female or the penis in the male, particularly during fetal development of the urinary and reproductive organs, before sexual differentiation is evident. This is also the case for the immature male analog, the immature glans penis....

. In the human fetus

Fetus

A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 the genital tubercle develops around week 4 of gestation

Gestation

Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

, and by week 9 becomes recognizably either a clitoris

Clitoris

The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...

 or penis

Penis

The penis is a biological feature of male animals including both vertebrates and invertebrates...

.
This should not be confused with the sinus tubercle

Sinus tubercle

Sinus tubercle is the proliferation of endoderm induced by the paramesonephric ducts. The uterovaginal primoridium, which is a fusion of the caudal ends of paramesonephric ducts contacts the dorsal wall of the urogenital sinus and, induces the formation of the sinus tubercle...

 which is a proliferation of endoderm induced by paramesonephic ducts.
Even after the phallus is developed, the term genital tubercle remains, but only as the terminal end of it, which develops into either the glans penis

Glans penis

The glans penis is the sensitive bulbous structure at the distal end of the penis. The glans penis is anatomically homologous to the clitoral glans of the female...

 or the glans clitoridis.

The genital tubercle is sensitive to dihydrotestosterone

Dihydrotestosterone

Dihydrotestosterone is an androgen or male sex hormone. The enzyme 5α-reductase synthesises DHT in the prostate, testes, hair follicles, and adrenal glands...

 and rich in 5-alpha-reductase, so that the amount of fetal testosterone

Testosterone

Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

present after the second month is a major determinant of phallus size at birth.

External links

• Overview at mcgill.ca