Lecture 10: Pelvic diaphragm and perineum Flashcards
Pelvic cavity
- Pelvis cavity is a space surrounded by the pelvic girdle.
- Area of transition between the trunk & lower limbs.
- Bony components of pelvic girdle: ➢Right and left hip (innominate/pelvic)
bones and sacrum. - Pelvic cavity subdivided by pelvic brim (pelvic inlet) into:
- Greater (false) pelvis (contains the inferior abdominal viscera).
- Lesser (true) pelvis includes pelvic cavity.
- Pelvic cavity walls: antero-inferior, posterior, 2 lateral, floor.
- Pelvic outlet – includes inferior pelvic aperture.
Lateral pelvic walls are covered by
obturator internus muscles:
➢Obturator fascia thickened to form tendinous arch.
Posterolateral wall contains
piriformis muscle.
Pelvic floor is formed by:
➢ Pelvic diaphragm muscles (coccygeus and levator ani).
Pelvic floor location
in the pelvic outlet.
Pelvic floor is attached to the
tendinous arch
Pelvic Floor: Pelvic diaphragm
Formed by pelvic diaphragm muscles:
Coccygeus and levator ani muscles.
Pelvic Floor: Pelvic diaphragm
Formed by pelvic diaphragm muscles:
Separates
pelvic cavity from perineum.
Coccygeus: Origin
from lateral aspect of inferior sacrum & coccyx
Coccygeus: distal
attaches to sacrospinous ligament
Levator ani:
attached anteriorly to pubic bones, ischial spines posteriorly & tendinous arch laterally.
➢Like a hammock between the bones of the pelvis.
➢Anterior gap between medial borders:
- urogenital hiatus.
- passage for urethra (& vagina in females).
Levator ani is composed of 3 muscles:
Puborectalis
Pubococcygeus
Iliococcygeus
Puborectalis:
runs from posterior pubis and forms a sling around rectum.
➢Forms boundary of urogenital hiatus.
Pubococcygeus:
runs from posterior pubis & tendinous arch to coccyx, join in the midline to form anococcygeal ligament (extends from anus to coccyx).
➢Lateral to puborectalis.
➢Gives off muscular slips to midline structures: puboprostaticus (males), pubovaginalis (females), puboanalis.
Iliococcygeus:
runs from tendinous arch & ischial spine to anococcygeal ligament.
➢Most posterolateral of the three muscles.
Levator ani functions
supports pelvic viscera:
➢Maintains closure of rectum and vagina.
➢Puborectalis: maintains the perineal flexure (angle) – keeps rectum closed (continence).
➢supports posterior pelvic floor.
Pelvic diaphragm
Perineum is the
Diamond-shaped region between the thighs, inferior to the pelvic floor
Perineum is bounded by
pelvic outlet and separated from pelvic cavity by pelvic diaphragm.
Perineum contains:
anal canal, urethra, vagina (females) & external genitalia.
Perineum borders:
➢Anterior – pubic symphysis.
➢Anterolateral – inferior pubic rami and ischial rami.
➢Lateral – ischial tuberosities.
➢Posterolateral – sacrotuberous ligaments.
➢Posterior – sacrum and coccyx.
Perineum divided into 2 triangles
by a line drawn between ischial tuberosities:
➢Urogenital triangle: contains urethra & external genitalia.
➢Anal triangle: contains anus & external anal sphincter.
Urogenital triangle:
Perineal membrane
- Urogenital hiatus – is the U shaped defect in anterior part of levator ani muscles.
- “Filled in” by the perineal membrane:
➢Thick fibrous sheet.
➢Free posterior border, anchored in posterior midline to perineal body, attached laterally to pubic arch.
Urogenital triangle: Perineal body
irregular mass containing collagen and elastic fibers, skeletal and smooth muscle.
Perineal body lies
deep to skin, posterior to vaginal vestibule/ bulb of penis, anterior to anus and anal canal.
Anterior part of perineal body
blends with perineal membrane, superior part with rectovesical (males) or rectovaginal septum (females).
Perineal body is a site of convergence of muscles:
➢Bulbospongiosus.
➢External anal sphincter.
➢Superficial and deep transverse perineal.
➢Smooth & voluntary slips from external urethral sphincter, levator ani.
Urogenital triangle: Perineal pouches
- Perineal membrane divides urogenital triangle into two pouches/spaces:
- Deep perineal pouch is superior to perineal membrane.
➢Contains skeletal muscle (external urethral sphincter, deep transverse perineal) & neurovascular tissues.
➢Pierced by urethra in male, urethra & vagina in female. - Superficial perineal pouch is below (superficial to) perineal membrane.
- Contains the external genitalia & associated skeletal muscles (Superficial transverse perineal, bulbospongiosus, ischiocavernosus).
Superficial perineal space: Contents Male
- Bulb and crura of penis.
- Proximal spongy urethra.
- Superficial transverse perineal muscles.
- Bulbospongiosus muscles.
- Ischiocavernosus muscles.
- Deep perineal vessels & dorsal nerve of penis.
Superficial perineal space: Contents Female
- Clitoris and bulbs of the vestibule.
- Greater vestibular glands.
- Superficial transverse perineal muscles.
- Bulbospongiosus muscles.
- Ischiocavernosus muscles.
- Deep perineal vessels & dorsal nerve of clitoris.
Perineal muscles:
Function
- Perineal muscles: assists in urination in both sexes.
- Ejaculation in males.
- Strengthen pelvic floor/perineal body.
- Assists & maintains erection of penis (males) and clitoris (females).
- Bulbospongiosus compresses bulb of penis to expel last drops of urine/semen.
- More well developed in males.
Nerve supply of perineal muscles
- Muscles of perineum: bulbospongiosus, ischiocavernosus, superficial and deep transverse perineal:
➢deep branch of perineal nerve, branch of pudendal nerve (S2, S3, S4). - External urethral sphincter:
➢dorsal nerve of penis or clitoris (terminal branch of pudendal nerve, S2, S3, S4). - External anal sphincter by inferior rectal nerve (branch of pudendal nerve, S2, S3, S4).
Urogenital diaphragm consists of
The deep perineal muscles:
* Paired deep transverse perineal.
* External urethral sphincter.
AND
Fascial coverings:
* The inferior fascia –perineal membrane.
* Superior fascia (continuous with pelvic fascia).
