Pelvic Floor Anatomy

The Pelvic Floor - Overview and Function

The pelvic floor is an area of muscle and connective tissue that spans the area underneath the pelvis, separating the pelvic cavity above from the perineal region below. It provides support to the pelvic viscera including the bladder, intestines and uterus (in females). It also assists with continence through control of the urinary and anal sphincters. It facilitates birth by resisting the descent of the presenting part, causing the fetus to rotate forwards to navigate through the pelvic girdle. Finally , it helps to maintain optimal intraabdominal pressure.

Osteology, Ligaments and Fascia

Ligaments

Puboprostatic ligament

Pubovesical ligament

Sacrogenital ligaments

Superior pubic ligament - runs between pubic tubercles

Inferior arcuate ligament - runs between inferior pubic rami and blends with fibrocartilagnous disc of pubic symphysis

Anterior pubic ligament

Posterior pubic ligament - membranous structure which blends with periosteum

Ventral sacrococcygeal ligament

Dorsal sacrococcygeal ligament

Lateral sacrococcygeal ligament

Interosseous sacro-iliac ligament

Ventral sacro-iliac ligament

Sacrotuberous ligament

Sacrospinous ligament

Iliolumbar ligament

Pelvic Fascia

Parietal pelvic fascia - lines the internal surface of the muscles of the pelvic floor and walls

Visceral pelvic fascia - invests each pelvic organ

The parietal and visceral fascia are continuous where organs penetrate the pelvic floor. They thicken to form the arcus tendineus, arches of fascia running adjacent to the viscera from the pubis to the sacrum.

Endopelvic fascia - "filler" material lying bewteen the parietal and visceral fascia, sometimes condensing to form fibrous fascial septa which separate the organs.

• Hypogastric sheath - separates retropubic space from presacral space; conduit for vessels and nerves
• Transverse cerical (cardinal) ligaments - part of hypogastric sheath; runs from lateral pelvic wall to uterine cervix and vagina; transmits uterine artery and provides passive support for the uterus
• Vesicovaginal septum
• Rectovesical septum
• Rectovaginal septum

Pelvic Floor Myology

Pelvic Floor

Sacral and Coccygeal Plexus

Layer One - Urogenital Triangle

• Bulbocavernosus (bulbospongiosus in men)
• Ischiocavernosus
• Superficial transverse perineal
• External anal sphincter

Layer Two - Urogenital Diaphragm

• Urethral sphincter (sphincter urethrae)
• Compressor urethrae
• Sphincter urethral vaginalis
• Deep transverse perineal
• Perineal membrane

Layer Three - Pelvic Diaphragm

• Levator ani (pubococcygeus aka pubovisceral, pubovaginalis, puboanalis, puborectalis, iliococcygeus
• Ischiococcygeus (Coccygeus)
• Piriformis
• Obturator internus
• Arcus tendinous of levator ani
• Arcus tendinous fasciae pelvis

Muscle	Origin	Insertion	Action	Innervation
Levator Ani (Pubococcygeus)	Posterior aspect of body of pubis and anterior part of arcus tendineus	Coccyx and anococcygeal ligament	Helps to support pelvic viscera and resists increase in intra-abdominal pressure	Nerve to levator ani (branches of S4), inferior rectal nerve (from pudendal nerve - S3, S4), coccygeal plexus
Levator Ani (Iliococcygeus)	Posterior aspect of arcus tendineus and the ischial spine	Anococcygeal raphe and the coccyx	Helps to support pelvic viscera and resists increase in intra-abdominal pressure	Nerve to levator ani (branches of S4), inferior rectal nerve (from pudendal nerve - S3, S4), coccygeal plexus
Levator Ani (Puborectalis)	Lower part of pubic symphysis and superior fascia of urogenital diaphragm	Unites with its partner to make a U-shaped sling around the rectum	Controls defecation by pulling anorectal junction forward	Nerve to levator ani (branches of S4), branch of pudendal nerve (S2-4)
Ischiococcygeus (Coccygeus)	Ischial Spine	Lower two sacral and upper two coccygeal spinal segments, blends with sacrospinous ligament on its external surface	Supports pelvic viscera, flexion of coccyx	Anterior rami of S4 and S5
External anal sphincter	Skin and fascia surrounding the anus and coccyz via the anococcygeal body	Perinal body	Closes anal canal	Inferior rectal (anal) nerve
Sphincter urethrae	Inferior aspect of pubic ramus and ischial tuberosity	Surrounds urethra; in females, some fibres also enclose the vagina	Controls flow of urine through urethra; also compresses vagina in females	Deep branch of perineal nerve (branch of pudendal nerve)
Superficial transverse perineal	Ischial ramus and tuberosity	Perineal body	Supports perineal body	Deep branch of perineal nerve (branch of pudendal nerve)
Deep transverse perineal	Inner aspect of ischiopubic ramus	Median raphe, perineal body and external anal sphincter	Fixes perineal body	Deep branch of perineal nerve (branch of pudendal nerve)
Bubospongiosus	Male: median raphe, ventral surface of bulb of penis; Female: perineal body	Male: Corpora spongiosum and cavernosa, fascia of bulb of penis; Female: fascia of corpus cavernosa	Male: Compression of bulb of penis and assists erection; Female: reduces lumen of vagina and assists erection of clitoris	Deep branch of perineal nerve (branch of pudendal nerve)
Ischiocavernosus	Ischial ramus and tuberosity	Crus of penis or clitoris	Maintains erection of penis or clitoris by compression of outflow veins	Deep branch of perineal nerve (branch of pudendal nerve)