Lecture 10: Pelvic diaphragm and perineum

Question 1

Pelvic cavity

Answer 1

• 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.

Question 2

Question 3

Lateral pelvic walls are covered by

Answer 3

obturator internus muscles:
➢Obturator fascia thickened to form tendinous arch.

Question 4

Posterolateral wall contains

Answer 4

piriformis muscle.

Question 5

Pelvic floor is formed by:

Answer 5

➢ Pelvic diaphragm muscles (coccygeus and levator ani).

Question 6

Pelvic floor location

Answer 6

in the pelvic outlet.

Question 7

Pelvic floor is attached to the

Answer 7

tendinous arch

Question 8

Question 9

Question 10

Pelvic Floor: Pelvic diaphragm
Formed by pelvic diaphragm muscles:

Answer 10

Coccygeus and levator ani muscles.

Question 11

Pelvic Floor: Pelvic diaphragm
Formed by pelvic diaphragm muscles:
Separates

Answer 11

pelvic cavity from perineum.

Question 12

Coccygeus: Origin

Answer 12

from lateral aspect of inferior sacrum & coccyx

Question 13

Coccygeus: distal

Answer 13

attaches to sacrospinous ligament

Question 14

Levator ani:

Answer 14

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).

Question 15

Levator ani is composed of 3 muscles:

Answer 15

Puborectalis
Pubococcygeus
Iliococcygeus

Question 16

Question 17

Puborectalis:

Answer 17

runs from posterior pubis and forms a sling around rectum.
➢Forms boundary of urogenital hiatus.

Question 18

Pubococcygeus:

Answer 18

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.

Question 19

Iliococcygeus:

Answer 19

runs from tendinous arch & ischial spine to anococcygeal ligament.
➢Most posterolateral of the three muscles.

Question 20

Levator ani functions

Answer 20

supports pelvic viscera:
➢Maintains closure of rectum and vagina.
➢Puborectalis: maintains the perineal flexure (angle) – keeps rectum closed (continence).
➢supports posterior pelvic floor.

Question 21

Pelvic diaphragm

Question 22

Perineum is the

Answer 22

Diamond-shaped region between the thighs, inferior to the pelvic floor

Question 23

Perineum is bounded by

Answer 23

pelvic outlet and separated from pelvic cavity by pelvic diaphragm.

Question 24

Perineum contains:

Answer 24

anal canal, urethra, vagina (females) & external genitalia.

Question 25

Perineum borders:

Answer 25

➢Anterior – pubic symphysis. ➢Anterolateral – inferior pubic rami and ischial rami. ➢Lateral – ischial tuberosities. ➢Posterolateral – sacrotuberous ligaments. ➢Posterior – sacrum and coccyx.

Question 26

Perineum divided into 2 triangles

Answer 26

by a line drawn between ischial tuberosities: ➢Urogenital triangle: contains urethra & external genitalia. ➢Anal triangle: contains anus & external anal sphincter.

Question 27

Question 28

Question 29

Urogenital triangle: Perineal membrane

Answer 29

* 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.

Question 30

Question 31

Question 32

Urogenital triangle: Perineal body

Answer 32

irregular mass containing collagen and elastic fibers, skeletal and smooth muscle.

Question 33

Perineal body lies

Answer 33

deep to skin, posterior to vaginal vestibule/ bulb of penis, anterior to anus and anal canal.

Question 34

Anterior part of perineal body

Answer 34

blends with perineal membrane, superior part with rectovesical (males) or rectovaginal septum (females).

Question 35

Perineal body is a site of convergence of muscles:

Answer 35

➢Bulbospongiosus. ➢External anal sphincter. ➢Superficial and deep transverse perineal. ➢Smooth & voluntary slips from external urethral sphincter, levator ani.

Question 36

Question 37

Urogenital triangle: Perineal pouches

Answer 37

* 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).

Question 38

Question 39

Question 40

Superficial perineal space: Contents Male

Answer 40

* Bulb and crura of penis. * Proximal spongy urethra. * Superficial transverse perineal muscles. * Bulbospongiosus muscles. * Ischiocavernosus muscles. * Deep perineal vessels & dorsal nerve of penis.

Question 41

Question 42

Superficial perineal space: Contents Female

Answer 42

* Clitoris and bulbs of the vestibule. * Greater vestibular glands. * Superficial transverse perineal muscles. * Bulbospongiosus muscles. * Ischiocavernosus muscles. * Deep perineal vessels & dorsal nerve of clitoris.

Question 43

Question 44

Perineal muscles: Function

Answer 44

* 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.

Question 45

Question 46

Nerve supply of perineal muscles

Answer 46

* 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).

Question 47

Question 48

Question 49

Urogenital diaphragm consists of

Answer 49

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).

Question 50

Question 51