Vagina
The vagina is a muscular tube that extends upward and backward
from the vulva to the uterus. It measures about 3 in. (8 cm) long and has
anterior and posterior walls, which are normally in apposition. At its upper end,
the anterior wall is pierced by the cervix, which projects downward and
backward into the vagina. It is important to remember that the upper half of
the vagina lies above the pelvic floor and the lower half lies within the
perineum. The area of the vaginal lumen, which surrounds the cervix, is divided
into four regions, or fornices: anterior, posterior, right lateral, and left
lateral. The vaginal orifice in a virgin possesses a thin mucosal fold called
the hymen, which is perforated at its center. After childbirth, the hymen
usually consists only of tags
Relations
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Anteriorly: The vagina is closely related to the bladder above and to the
urethra below.
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Posteriorly: The upper third of the vagina is related to the rectouterine pouch
(pouch of Douglas) and its middle third to the ampulla of the rectum. The lower
third is related to the perineal body, which separates it from the anal canal.
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Laterally: In its upper part, the vagina is related to the ureter; its middle
part is related to the anterior fibers of the levator ani, as they run backward
to reach the perineal body and hook around the anorectal junction. Contraction
of the fibers of levator ani compresses the walls of the vagina together. In
its lower part, the vagina is related to the urogenital diaphragm and the bulb
of the vestibule.
Function
The vagina not only is the female genital canal, but it also
serves as the excretory duct for the menstrual flow and
Supports
of the Vagina
The upper part of the vagina is supported by the levatores ani
muscles and the transverse cervical, pubocervical, and sacrocervical ligaments.
These structures are attached to the vaginal wall by pelvic fascia. The middle
part of the vagina is supported by the urogenital diaphragm. The lower part of
the vagina, especially the posterior wall, is supported by the perineal body.
Vaginal
Examination
The anatomic relations of the vagina are of great clinical
importance. Many pathologic conditions occurring in the female pelvis may be
diagnosed using a simple vaginal examination.
The following structures can be palpated through the vaginal
walls from above downward:
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Anteriorly: The bladder and the urethra
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Posteriorly: Loops of ileum and the sigmoid colon in the rectouterine peritoneal
pouch (pouch of Douglas), the rectal ampulla, and the perineal body
■■
Laterally: The ureters, the pelvic fascia and the anterior fibers of the
levatores ani muscles, and the urogenital diaphragm
Prolapse
of the Vagina
The vaginal vault is supported by the same structures that support
the uterine cervix. Prolapse of the uterus is necessarily associated with some
degree of sagging of the vaginal walls. However, if the supports of the
bladder, urethra, or anterior rectal wall are damaged in childbirth, prolapse
of the vaginal walls occurs, with the uterus remaining in its correct position.
Sagging of the bladder results in the bulging of the
anterior wall of the vagina, a condition known as a cystocele. When the ampulla
of the rectum sags against the posterior vaginal wall, the bulge is called a
rectocele.
Vaginal
Trauma
Coital injury, picket fence–type of impalement injury, and
vaginal perforation caused by water under pressure, as occurs in water skiing,
are common injuries. Lacerations of the vaginal wall involving the posterior
fornix may violate the pouch of Douglas of the peritoneal cavity and cause
prolapse of the small intestine into the vagina
forms part of the birth canal.
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