The female levator ani muscle

Anatomy Quiz: Week 38
4/22/2013 3:25:00 PM
1. Describe and demonstrate the bony landmarks of the pelvis on an
articulated pelvis and on a plain film x-ray. Compare and contrast
the shape of the female bony pelvis with that of the typical male
bony pelvis.
I’m imagining that the following bony landmarks are eligible (from his list):
 Iliac fossae
 Iliopubic eminence
 Arcuate line
 Pectineal line
Superior pubic ramus
Public symphysis
Pubic arch
Ischiopubic ramus
Obturator foramen
Ischial tuberosity
Ischial spine
Sacral promontory
Anterior sacral foramina
 Coccyx
I tried making a diagram and then I remembered that you all have books
2. Demonstrate the boundary structures and content of the
urogenital and anal triangles on the bony pelvis.
Urogenital Δ
Boundaries: the vertices of the triangle are at the public symphysis
and the two ischiopubic rami. It is the anterior triangle of the
o Bulbospongiosus, ischiocavernosus, transversus perinei
superficialis mm.
o Crus of penis/ clitoral crura
o Urethra
o Bulbourethral gland (male)/ Bartolin’s gland (female)
o Penis bulb, (yup) / vestibular bulb
o Posterior scrotal or labial nerves
Anal Δ
Boundaries: the vertices are at the coccyx and the two ischiopubic
rami. Posterior triangle of the perineum
o Sacrospinous & sacrotuberous ligaments
o Pudendal nerve
o Internal pudendal a/v
o Anal canal
o Muscles
 Sphincter ani externus
 Gluteus maximus
 Obturator internus
 Levator ani
 Coccygeus
o Ischioanal fossa
3. Describe the boundaries of the ischiorectal fossa from a posterior
approach and describe the construction, attachments and
functions of the components of levator ani in a female.
The ischiorectal fossae are fat-filled, wedge-shaped, fascia-lined spaces
between the pelvis diaphragm and the perianal skin. The boundaries are:
 Laterally; ischium, inferior obturator internus m., obturator fascia
 Medially; external anal sphincter, levator ani m.
 Posteriorly; sacrotuberous ligament, gluteus maximus
 Anteriorly; pubic bodies, inferior to the origin of puborectalis.
The female levator ani muscle
 Puborectalis
o Forms the sling for the rectum
o Originates from inferior public symphysis and insert on the
opposing puborectalis muscle
o It lets you hold in a load when it might not be socially
acceptable to dump it (wait, girls poop?)
o N: S3, S4
o Hammock-shaped muscle from pubis to coccyx and forms the
floor of the pelvic cavity
o Joins iliococcygeus in forming the anococcygeal raphe
o Controls urine flow, aids in childbirth, contracts during orgasm
o N: S3, S4
o The most posterior of the group, from the ischial spine to the
anococcygeus raphe, via the tendinous arch of the obturator
o Pulls the coccyx side to side and elevates the rectum
o N: S3, S4
4. Describe the spermatic cord fascial layers including their
embryological origin from the anterior abdominal wall structures.
3 Layers
External Spermatic Fascia
o derived from external oblique muscle
o outermost covering of spermatic cord (& testes)
Cremasteric Fascia
o derived from internal oblique muscle
Internal Spermatic Fascia
o derived from transversalis fascia
5. Contrast and compare the arrangement of erectile tissue in the
male and female genitalia.
Male: 3 cylindrical cavernous bodies
 Paired corpora cavernosa dorsally
 Single corpus spongiosum ventrally
The anatomical position for the penis is while erect. So dorsal is the side
that’s easiest for his owner to view.
Female: way more complicated than previously thought…
o At the anterior juncture of labia minora
o Composed of two crura, two corpora cavernosa, and glans
 Glans is highly innervated
 Crura attach the clitoris to the inferior pubic rami
 Body of clitoris is covered by prepuce
Bulbs of the Vestibule
o Paired elongated masses of erectile tissue along the vaginal
orifice, deep to the labia minora.
o Homologous to the male’s bulb of the penis
And, in conclusion, I present these schematics. Way more similar that I
imagined. Gravy.
6. Compare and contrast the course of the urethra in the male and
the female.
Male (18-22cm)
1. Intramural / Preprostatic
 1.5cm, vertically from the bladder, size depends on bladder status
2. Prostatic
 3-4cm, descends through anterior prostate, very distensible
3. Intermediate (membranous)
 1.0-1.5cm, through deep perineal pouch
4. Spongy
Through the corpus spongiosum and out into the external
Length doesn’t matter, right?
Female (4cm long)
From the internal urethral orifice of bladder, descends posterior to
the pubic symphysis and then inferior to it, to the external urethral
orifice. This is located in the vestibule of the vagina.
7. Trace the fascial layers of the abdomen as they descend into the
As your cross into the pelvic region, Camper’s subcutaneous fatty fascia
could be present in variable amounts, and probably gets renamed in the
pelvis. The deep investing fascia from the abdominal muscles continues as
the outer fascial covering for pelvic musculature (piriformis, obturator
The final layer is the endoabdominal (aka transversalis fascia). This
becomes the pelvic fascia proper and can be divided into parietal and
visceral layers. The parietal layer invests the deep aspects of pelvic
musculature and the floor of the pelvis. Often, regions are named for the
muscle it is directly covering. The visceral layer directly forms the
adventitial layer of the pelvic organs. Where organs penetrate the pelvic
floor, the parietal and visceral will blend together.