Pelvic floor

Levator ani and coccygeus, also called the pelvic diaphragm

Pelvis · funnel of muscle closing the pelvic outlet

A funnel- or hammock-shaped sheet of muscles that closes the bottom of the pelvic cavity, separating it from the perineum below. It is made of the levator ani, itself three muscles, and the coccygeus, and it supports the bladder, womb and rectum, resists rises of abdominal pressure, and is a sphincter for the urethra and anal canal. Gaps in it let the urethra, the vagina in women and the anal canal pass through.

How to spot them

▸A funnel of muscle attached to the pubic bone in front, the ischial spine at the side and the coccyx behind
▸Levator ani has three parts, puborectalis, pubococcygeus and iliococcygeus, and is joined by the small coccygeus
▸A urogenital hiatus in front for the urethra (and vagina) and a rectal hiatus behind for the anal canal, with the perineal body between
▸Supplied by the nerve to levator ani (S3 to S4) and the pudendal nerve

What to know

A funnel-shaped sheet of muscles closing the outlet of the bony pelvis and supporting the bladder, womb and rectum

Pelvic floor — the pelvic diaphragm, made of levator ani and coccygeus.

Its most important part forms a U-shaped sling round the junction of the rectum and anal canal, bending the canal forwards

Pelvic floor — puborectalis, which creates the anorectal angle that helps to keep the bowel continent.

Three paired muscles that arise from the pubis and the tendinous arch over the obturator internus and pass back to the coccyx and the perineal body

Pelvic floor — levator ani: puborectalis, pubococcygeus and iliococcygeus.

A series of squeeze-and-hold exercises named for an American gynaecologist who introduced them in 1948 aims to strengthen it after childbirth

Pelvic floor — Kegel exercises, after Arnold Kegel.

Weakening after childbirth, ageing or chronic straining can lead to leakage of urine or a bulge of the pelvic organs into the vagina

Pelvic floor — stress incontinence and pelvic organ prolapse.

A fibrous knot in the middle between the vaginal opening and the anus anchors it and can be torn in childbirth

Pelvic floor — the perineal body.

Supplied by a nerve from S3 and S4 above and by the nerve that runs through the pudendal canal below

Pelvic floor — the nerve to levator ani and the pudendal nerve.

Key ideas

The muscle sheet is in constant low-grade contraction, closing the urethra and anal canal, and relaxes only for urination and defecation; it also contracts reflexly before a cough or sneeze to resist the sudden rise in abdominal pressure.
Because the levator ani forms both a floor and a sphincter, injury to it (avulsion from the pubic bone in a difficult vaginal delivery) can leave the pelvic organs poorly supported.

Quick-fire facts

•Levator ani (the largest part): puborectalis, pubococcygeus and iliococcygeus; the other muscle is the coccygeus, sometimes called ischiococcygeus
•Attachments: the back of the pubic bone, the tendinous arch of levator ani on the obturator fascia and the ischial spine, running to the coccyx, the anococcygeal ligament and the perineal body
•Nerve supply: the nerve to levator ani (S3 to S4) and branches of the pudendal nerve; the coccygeus by S4 and S5
•Blood supply: the inferior vesical, inferior gluteal and pudendal arteries
•The two main gaps are the urogenital hiatus (urethra, vagina) and the rectal hiatus (anal canal)
•The perineal body lies between the urogenital hiatus and the anal canal and joins the pelvic floor to the perineum
•The puborectalis is the most important part for faecal continence, forming the anorectal angle
•Functions: support of the abdominopelvic viscera, resistance to increases in intra-abdominal pressure, and urinary and faecal continence
•Pelvic floor dysfunction includes urinary and faecal incontinence, prolapse and pelvic pain; obstetric trauma is a leading cause
•Arnold Kegel published the pelvic floor exercises named for him in 1948

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Sources

TeachMeAnatomy — The pelvic floor