Typical anatomy & Embryological Origins
• Distal vagina arises from the endodermal urogenital sinus
- Recall that this is a point of contention; other research indicates the distal vagina arises from the paramesonephric ducts.
• Proximal vagina, uterus, and uterine tubes are derived from the paramesonephric ducts.
• Ovaries are located near the distal ends of the uterine tubes.
Atresia
• Results from incomplete canalization of lumen.
• Can be vaginal or cervical.
• Can be complete or incomplete.
- In some women, dilators can be used to non-surgically correct vaginal atresia; in others, vaginoplastic surgery is needed to create a functional vagina.
• Vaginal atresia may be noticed during neo-natal examination, but cervical atresia often goes undiagnosed until puberty
- Amenorrhea (absence of menstrual flow) and abdominal pain signify disorder. - - However, because the two often
occur together, findings of vaginal atresia warrant inspection of the cervix via ultrasound.
Incomplete fusion of the paramesonephric ducts
aka, Müllerian ducts
• Anomalies of the uterus.
5-class schema based on the type of malformation
• Distinction between the types is important, because some classes are associated with higher risks of infertility and pain.
Class I comprises Müllerian hypoplasia and agenesis.
• For example, cervical agenesis is characterized by the absence of the cervix.
- Other variants include vaginal and/or uterine tube absence or underdevelopment.
Class II anomalies arise when development one of the paramesonephric ducts is arrested, producing a unicornuate,
aka, single-horned, uterus.
• It’s helpful to know that “uni” means “one”, and “cornuate” means “horn”; the uterus typically has two horns, i.e., where the uterine tube meets the body of the uterus
• Unicornuate uteri can present in 4 basic variations, based on how the “rudimentary” horn develops.
- A communicating hemiuterus connects the primary uterine cavity with that of the rudimentary horn. Be aware that the
non-communicating horn with a cavity can present as abdominopelvic pain because of obstructed menstrual flow.
- Additional variants include uteri with no rudimentary horns, with rudimentary horns with non-communicating cavities,
and rudimentary horns with no cavities.
Be aware that some authors refer to unicornuate uteri as “banana shaped.”
Class III comprises the didelphys, aka, double uterus
Though not typical in humans, the double uterus is common in other animals, including cats and dogs.
• Two uteri open to the vagina via separate cervical openings; though it is possible to carry two fetuses to term, one in
each uterus, this phenomenon is rare.
• In some cases, a septum divides the vaginal canal to form double vaginas.
Class IV comprises the bicornuate uterus
• The bicornuate uterus has two distinct horns separated by a cleft, thus, they appear “heart-shaped.”
• This condition is the result of incomplete fusion of the paramesonephric ducts; incidentally, the horns may be
undeveloped.
Class V comprises the septate defects.
• The most common Müllerian duct anomalies.
• The septum of the uterus arises from the inner wall of the fundus and extends towards the cervix.
• The septum is created by incomplete resorption of the paramesonephric duct septum.
• It may comprise fibrous or muscular tissue; tissue type informs surgical intervention.
Final Notes:
Be careful not to confuse the septate uterus with the bicornuate uterus; notice that the septum divides the inner uterine
cavity, but the cleft of the bicornuate uterus is visible on the external surface of the uterine fundus (the superior most
region of the uterus). This distinction is clinically important, as the septate uterus is more often associated with
reproductive impairment than is the bicornuate uterus.