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Describe the development of the uterus and vagina

Introduction: the paramesonephric or mullerian duct develops into the uterine tubes, uterus and the proximal part of the vagina. The paramesonephric duct is divided into three parts:
a. A cranial vertical part. It opens into the coelomic cavity.
b. A horizontal part, which crosses the mesonephric duct.
c. A caudal part, which fuses with the opposite one.
Development of the uterus.
The caudal parts of the two paramesonephric ducts fuse together to form the uterus. After fusion a broad transverse pelvic fold called the broad ligament of the uterus is formed. It extends from the lateral sides if the fused ducts to the wall if the pelvis. The fused paramesonephric ducts give rise to the corpus (body) and cervix of the uterus. They are surrounded by a layer of mesenchyme. Later, this mesenchyme forms the muscular coat of the uterus, the myometrium and its peritoneal covering, the perimetrium.
Development of the vagina.
After the fused tips of the paramesonephric ducts have reached the urogenital sinus, two solid evaginations, the sinovial bulbs, grow out from the pelvic part of the sinus. They proliferate and form the vaginal plate. Due to further proliferation of the cranial end of the plate the distance between the uterus and urogenital sinus increase. By the fifth month of development the vaginal outgrowth is canalized. The vaginal fornicles are of paramesonephric duct while the lower portion is from the urogenital sinus.
Anomalies: different types of anomalies of the uterus or vagina occur due to lack of fusion of the paramesonephric ducts in an area.
a. Uterus didelphys with double vagina: in this case the uterus is completely double.
b. Uterus arcuatus: the uterus has a slight indentation in the middle.
c. Uterus bicornis: the uterus has two horns entering the common vagina.
d. Uterus bicornis unicollis with one rudimentary horn: this is due to atresia of one of the paramesonephric ducts. The rudimentary part lies as an appendage to the well developed side.
e. Atresia of the cervix: develops due to partial atresia of both paramesonephric ducts.
f. Atresia of the vagina: this is caused if the sinovaginal bulb do not develop.
g. Double vagina: this is due to non-fusion of the sinovaginal bulbs.

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