Urogenital sinus
Encyclopedia
The definitive urogenital sinus (also known as the persistent cloaca) is a part of the human body only present in the development of the urinary and reproductive organs
. It is the ventral part of the cloaca, formed after the cloaca
separates from the anal canal
during the fourth to seventh weeks of development.
In males, the UG sinus is divided into three regions: upper, pelvic, and phallic. The upper part gives rise to the urinary bladder
and the pelvic part gives rise to the prostatic and membranous parts of the urethra
.
In females, the pelvic part of the UG sinus gives rise to the sinovaginal bulbs, structures that will eventually form the inferior portion vagina
. This process begins when the lower tip of the paramesonephric ducts, the structures that will eventually form the uterus
and vaginal fornices, come in contact with the UG sinus. Shortly afterwards, the sinovaginal bulbs form as two solid evaginations of the UG sinus. Cells in these bulbs divide to form a solid vaginal plate
, which extends and then canalizes (hollows) to form the inferior portion of the vagina
.
and vagina
both open into a common channel.
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 is the ventral part of the cloaca, formed after the cloaca
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
separates from the anal canal
Anal canal
The anal canal is the terminal part of the large intestine.It is situated between the rectum and anus, below the level of the pelvic diaphragm. It lies in the anal triangle of perineum in between the right and left ischioanal fossa....
during the fourth to seventh weeks of development.
In males, the UG sinus is divided into three regions: upper, pelvic, and phallic. The upper part gives rise to the urinary bladder
Urinary bladder
The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...
and the pelvic part gives rise to the prostatic and membranous parts of the urethra
Urethra
In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...
.
In females, the pelvic part of the UG sinus gives rise to the sinovaginal bulbs, structures that will eventually form the inferior portion vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
. This process begins when the lower tip of the paramesonephric ducts, the structures that will eventually form the uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
and vaginal fornices, come in contact with the UG sinus. Shortly afterwards, the sinovaginal bulbs form as two solid evaginations of the UG sinus. Cells in these bulbs divide to form a solid vaginal plate
Vaginal plate
The vaginal plate is a precursor to the inferior portion of the vagina.They form from sinovaginal bulbs.-External links:* http://embryology.med.unsw.edu.au/Notes/genitalXXuterus.htm...
, which extends and then canalizes (hollows) to form the inferior portion of the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
.
Pathology
A urogenital sinus anomaly is also a rare birth defect in women where the urethraUrethra
In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...
and vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
both open into a common channel.
