Vagina

Shortly after the solid tip of the paramesonephric ducts reaches the urogenital sinus (Figs. 14.29A and 14.30A), two solid evaginations grow out from the pelvic part of the sinus (Figs. 14.29B and 14.30B). These evaginations, the sinovaginal bulbs, proliferate and form a solid vaginal plate. Proliferation continues at the cranial end of the plate, increasing the distance between the uterus and the urogenital sinus. By the fifth month, the vaginal outgrowth is entirely canalized. The winglike expansions of the vagina around the end of the uterus, the vaginal fornices, are of paramesonephric origin (Fig. 14.30C). Thus, the vagina has a dual origin, with the upper portion derived from the uterine canal and the lower portion derived from the urogenital sinus.

Vagina Fornices

Figure 14.29 Formation of the uterus and vagina. A. 9 weeks. Note the disappearance of the uterine septum. B. At the end of the third month. Note the tissue of the sinovaginal bulbs. C. Newborn. The fornices and the upper portion of the vagina are formed by vacuolization of the paramesonephric tissue, and the lower protion of the vagina is formed by vacuolization of the sinovaginal bulbs.

Figure 14.29 Formation of the uterus and vagina. A. 9 weeks. Note the disappearance of the uterine septum. B. At the end of the third month. Note the tissue of the sinovaginal bulbs. C. Newborn. The fornices and the upper portion of the vagina are formed by vacuolization of the paramesonephric tissue, and the lower protion of the vagina is formed by vacuolization of the sinovaginal bulbs.

Vagina Formation

Figure 14.30 Sagittal sections showing formation of the uterus and vagina at various stages of development. A. Nine weeks. B. End of third month. C. Newborn.

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  • robur
    What is a uterine septum?
    8 years ago

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