Atlas of Human Anatomy by Netter

Iliococcygeus

Posterior part of the levator ani Is thin and poorly developed

Arises from the posterior part of the arcus tendineus and the ischial spine

Attaches to the anococcygeal raphe and the coccyx

Puborectalis

A thickened band of muscle best seen inferior to the pubococcygeus

Unites with its partner to make a U-shaped sling around the rectum at its junction with the anus

Has a sphincter-like action by pulling the anorectal junction forward and contributing to anal continence

Medial muscle fibers of the pubococcygeus border the urogenital hiatus

Most anterior fibers insert into the urethra

Other fibers sweep behind the vagina or prostate and insert into the central perineal tendon, and are called the levator prostatae or

pubovaginalis

Coccygeus muscle

Reinforces pelvic floor posteriorly

Arises from ischial spine

Inserts on lower two sacral and upper two coccygeal segments

Blends with sacrospinous ligament on its external surface

Innervation of the levator ani and coccygeus muscles

Levator ani innervated by branches from the anterior rami of S3-S4 spinal nerves

Puborectalis also innervated by branch of pudendal nerve (S2,3,4)

Coccygeus supplied by branches of the anterior rami of S4-S5 spinal nerves

Functions of the levator ani

Acting together raise the pelvic floor to increase abdominal pressure, such as when coughing, sneezing, urinating, defecating, lifting

heavy objects.

Important in voluntary control of micturition (urinating)

Supports pelvic viscera

Supports head of the fetus

Muscles Lining the Lateral Walls of the Pelvis

Obturator internus muscle

Proximal attachment: pelvic surfaces of ischium and ilium and obturator membrane

Distal attachment: greater trochanter of femur

Innervated by nerve to obturator internus (L5, S1-S2)

Lateral rotator of thigh

Piriformis muscle

Proximal attachment: pelvic surfaces of S2-4 segments of sacrum, sacrotuberous ligament

Distal attachment: greater trochanter of femur

Innervated by ventral rami of S1-S2 spinal nerves

Lateral rotator of this

Muscle Proximal Attachment (Origin) Distal Attachment (Insertion) Innervation Main Actions

Obturator internusPelvic aspect of obturator

membrane and pelvic bones

Greater trochanter of femur Nerve of

obturator

internus

Rotates external thigh

laterally; abducts flexed

thigh at hip

Piriformis Anterior surface of second to

fourth sacral segments and

sacrotuberous ligament

Greater trochanter of femur Ventral rami

of S1-S2

Rotates external thigh

laterally; abducts flexed

thigh; stabilizes hip joint

Levator ani Body of pubis, tendinous arch

of obturator fascia, and ischial

spine

Perineal body, coccyx, anococcygeal

raphe, walls of prostate or vagina,

rectum, and anal canal

Ventral rami

of S3-S4,

perineal

nerve

Supports pelvic viscera;

raises pelvic floor

Coccygeus

(ischiococcygeus)

Ischial spine and

sacrospinous ligament

Inferior sacrum and coccyx Ventral rami

S4-S5

Supports pelvic viscera;

draws coccyx forward

Pelvic Fascia

Occupies space between peritoneum and muscles of the pelvic floor and walls

Parietal pelvic fascia lines the internal surface (facing the pelvic cavity) of the muscles of the floor and walls

Visceral pelvic fascia invests each of the pelvic organs

Visceral and parietal fascia are continuous where organs penetrate pelvic floor

Where they are continuous, fascia thickens to form the tendineus arch of pelvic fascia (arcus tendinous fasciae pelvis)

Arches are bilateral bands running from pubis to sacrum, adjacent to viscera

Puboprostatic ligament

Pubovesical ligament

Sacrogenital ligaments

Between parietal and visceral fascia is endopelvic fascia

Matrix or filler material

In certain areas, condenses and becomes more fibrous to form fascial "ligaments" or septa

Major condensation is the hypogastric sheath

Runs from lateral pelvic wall to pelvic viscera

Separates retropubic space from presacral space

Serves as a conduit for vessels and nerves

Transverse cervical (cardinal) ligaments are part of hypogastric sheath

Runs from lateral wall to the uterine cervix and vagina

Uppermost part is beneath broad ligament and transmits the uterine artery

Is sufficiently fibrous to provide passive support for the uterus