Anatomy of The Female Pelvis
A Basic knowledge of pelvic anatomy will allow you to understand why prolapse occurs and how it can be corrected. Refer to (Figure 2). The bony pelvis the framework to which the support structures of the pelvis are attached.
The levator ani muscle is the major muscle that provides support to the urethra, vagina, and rectum. Refer to (Figure 3). The levator ani arises from the pubic bone, the ischial spine, and the tendinous arc. The tenduous arc is a very important anatomic support in the pelvis because it forms the common insertion point for pelvic muscles including the levator ani muscles. The levator ani muscle extends from the left tendinous arc to the right tendinous arc, creating a hammock-like structure. This levator “hammock” has openings through which the vagina, rectum, and urethra traverse.
There are several fasccias that are important in providing pelvic support. Fascia is the tough fibrous tissue that envelopes muscles. The levator fascia covers both sides of the levator ani muscle. The “pelvic leaf” fuses with the “vaginal leaf” to insert into the tendinous arc. The pelvic leaf is called the endopelvic fascia. Refer to (Figure 4).
The vaginal leaf is called the peri-urethral fascia (at the level of the urethra), and the perivesical fascia (at the level of the bladder). Refer to (Figure 5) . Contained within the two leaves of the levator fascia are the pelvic organs to which it provides support: the urethra, bladder, vagina, and uterus.
Specialized regions of the levator fascia form critical ligamentory supports to maintain the relationships between the urethra, bladder, vagina, and uterus within the bony pelvis. These specialized regions are the pubourethral ligaments, the urethropelvic ligaments, the vesicopelvic fascia, and the cardinal ligaments. The pubourethral ligaments anchor the urethra to the undersurface of the pubic bone, providing midurethral support.
The urethropelvic ligaments are composed of the leaves of levator fascia (endopelvic and peri-urethral fascia) that attach the urethra to the tendinous arc. Refer to (Figure 6). This attachment ideThis attachment provides support to the urethra at times of increased abdominal pressure. Weakness of the urethropelvic ligaments is present in females with stress urinary incontinence. The vesicopelvic fascia is composed of the leaves of levator fascia at the level of the bladder (endopelvic and perivesical fascia), which anchor the bladder to the tendinous arc and pelvic side walls and provide bladder support. Weakness in vesicopelvic fascia is present in females with cystoceles. The prerectal and pararectal fascia are anatomically situated between the rectum and floor of the vagina. When these fascias become weakened, a rectocele results. The cardinal ligaments contain the uterine arteries and provide attachment of uterus to the pelvic side walls. The sacro-uterine ligaments provide attachment of the cervix to the bony sacrum. Weakness or separation of the cardinal and sacro-uterine ligaments gives rise to uterine prolapse, entercele, and vaginal vault prolapse.
The levator ani muscles and urogenitaldiaphragm provide support to the rectum and perineum. The perineum is the anatomical region between the vagina and anus. The urogenital diaphragm consists of the bulbocavernosus muscle, transverse perineal muscle, external anal spincter, and central tendon. Refer to (Figure 7).
The vagina can be divided into proximal (deep), middle, and distal (superfiscial) thirds. The cardinal ligaments support the proximal third, the tendinous arc attachment the middle third, and the levators and perineal muscles the distal third. When pelvic floor relaxation occurs, the levator muscles and the urogenital diaphragm muscles become flaccid, allowing the openings for the urethra, vagina, and rectum to become enlarged and the normal angle of the vagina to become altered.Refer to (Figure 8). This creates widening of the vaginal opening and shortening of the distance between the vagina and anus, a situation called perineal laxity.