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NORMAL PELVIC FLOOR ANATOMY

1998; Elsevier BV; Volume: 25; Issue: 4 Linguagem: Inglês

10.1016/s0889-8545(05)70037-1

1558-0474

Kris Strohbehn,

Anorectal Disease Treatments and Outcomes

A dynamic coordinated system maintains the integrity of the pelvic floor. Normal control of the pelvic floor develops through learned behavior to provide for storage and evacuation in the bladder and anorectum. Because of the high prevalence of disorders of urinary incontinence,24 anal incontinence,75 pelvic organ prolapse,51 and combined pelvic support disorders34 in women, an understanding of the complex anatomy responsible for maintaining normal support is important. In a previous discussion of the anatomy of stress urinary incontinence, Strohbehn and DeLancey72 reviewed the anatomy of the pelvic floor. Some of the concepts reviewed in this article are derived and modified from that original review. Voluntary storage of urine and enteric contents occurs despite sudden changes in abdominopelvic pressures that accompany daily activities such as laughing, sneezing, coughing, positional changes, walking, bending, and standing. Pressures in the bladder of a healthy woman change from the supine to standing position by approximately 9 mm Hg (12 cm H2O), whereas maximal intraurethral pressures increase by a greater amount, 14 mm Hg.32 This difference in pressure between the bladder and urethra during the simple activity of standing is the result of coordinated reflexes that allow a woman to remain continent despite a stress added to the bladder. To maintain continence, the increased pressure in the urethra must be sustained while the individual remains standing. When intra-abdominal pressure increases, such as during a cough, anatomic compensations at the bladder outlet must precede or occur simultaneously to counter additional rises in bladder pressure. In support of the pelvic floor, each anatomic structure provides a functional contribution. Conceptually, it is useful to divide pelvic floor anatomy artificially into passive and active structures (Table 1)72 Examples of passive structures include the pelvic bones and connective tissue. Active support structures include neuromuscular structures that result in sustained (tonic) and intermittent voluntary pelvic floor muscle contractions during activity. The active support structures include the neurologic “wiring” to the pelvic floor muscles and the muscles themselves. The sections that follow review the different structures that contribute to passive and active support of the pelvic floor. The anatomy of bladder, urethra, and anorectum is reviewed with respect to pelvic floor support and continence.