7.04 Pelvis And Perineum Anatomy

Front 1

What are the upper and lower boundaries of the pelvic cavity?

Back 1

Upper: pelvic inlet
Lower: pelvic diaphragm

Front 2

What constitutes the bony pelvis?

Back 2

hip bones, sacrum, coccyx and associated joints

Front 3

What makes up the true pelvis?

Back 3

the space from pelvic inlet (sacroilliac and pubic symphsis) to outlet (iscial tuberosity and coccyx)

Front 4

Gynecologically, what is the orientation of a baby's head at the pelvic inlet and outlet?

Back 4

transverse at inlet, AP on outlet (as cavity is wider Tv at inlet and wider AP at outlet)

Front 5

What is the main difference between male and female pelvis?

Back 5

ischial tuberosity is wider apart in female (greater pubic angle)

Front 6

What is the shape of the pelvic cavity in males vs females?

Back 6

males - funnel shaped
females - wider fanned false pelvis and then a parallel, wider and shorter true pelvis

Front 7

What pelvic wall and floor muscles control the hip joint, and to what do they attach to?

Back 7

piriformis (attaches to coccyx, so moves with coccyx when weight is loaded on back)
obturator internus (attaches internally to femur)

Front 8

What are the two muscles of pelvic diaphragm?

Back 8

levator ani (main part)
coccygeus

Front 9

What are the attachments of levator ani?

Back 9

iscial spine, and also attaches to the fascia over obturator internus

Front 10

What is the coccygeus attached to?

Back 10

At its apex: ischial spine
At its base: sacral bone and coccyx

Front 11

What ligament runs alongside coccygeus?

Back 11

sacrospinous lig

Front 12

What does the pelvic diaphragm separate?

Back 12

pelvic cavity from perineum

Front 13

What is the gap between L and R levator ani?

Back 13

urogenital hiatus

Front 14

What is the function of levator ani (hint: its name)?

Back 14

pulls the rectum and anal canal towards pelvis - so, supports pelvic viscera and controls fecal continence
it also contracts with increased intraabdominal pressure (so if weak, will lead to stress incontinence)

Front 15

Is puborectalis tonically relaxed of contracted?

Back 15

contracted - defers defecation

Front 16

What are the peritoneal pouches?

Back 16

rectouterine pouch (the pouch from rectum to peritoneum)
uterovesical pouch (vesical = bladder, utero = in females only)
rectovesical pouch (from rectum to bladder - in males only)

Front 17

Toporgaphically where do the bladder, rectum and internal genitalia lie in males and females?

Back 17

bladder in front, rectum behind and internal genitalia in the middle

Front 18

What is the role of extraperitoneal tissue in the pelvic cavity (ie, loose connective fat, visceral and parietal fascia)?

Back 18

tissue condenses to support bladder, uterus and prostate

Front 19

How does infection spread quickly through pelvic cavity?

Back 19

through loose connection tissue

Front 20

Why is bleeding hard to locate in the pelvic cavity?

Back 20

there is a valveless plexus embedded within loose connective tissue and fat

Front 21

What outlines the diamond shape of perineum (and pubic outlet)?

Back 21

anterior: pubic symphysis
anterior triangle (urogenital triangle): ischopubic ramus and ischial tuberosity
posterior (anal triangle): coccyx

Front 22

What lies beneath the fascia of obturator internus?

Back 22

pudendal canal (containing pudendal nerve and vessels)

Front 23

What do the pudendal nerve and vessels supply?

Back 23

perineum

Front 24

Where can abscesses form in anal triangle? are the abscesses hemispherically isolated?

Back 24

in the fat and loose connective tissue of ischioanal fossa

it can spread in a horseshoe shape to the other side of the anal triangle and anteriorly to anterior recess of ischoanal fossa

Front 25

What fascia passes from superficial abdomen to superficial perineum?

Back 25

Scarpa's fascia (looks like silver skin)

Front 26

What fascia lies beneath skin of penis and is a continuation of Scarpa's fascia?

Back 26

superficial perineal fascia

Front 27

What provides an attachment point for erectile tissue and muscles covering the erectile tissue?

Back 27

perineal membrane (between levator ani)

Front 28

What muscle gives voluntary control of micturition? what muscle lies around it?

Back 28

sphincter urethra

(deep transverse perineal muscle lies around it)

Front 29

Where does the superficial fascia of perineum end?

Back 29

posteriorly to perineal membrane

Front 30

Where does blood and urine accumulate in males at rupture of urethra?

Back 30

in superficial perineal space,
in superficial perineal pouch, penis, scrotum and passing up to abdominal wall
but not in glans penis

Front 31

What is the perineal body comprised of?

Back 31

connective tissue (collagen, elastin), smooth muscle, skeletal muscle

Front 32

Where does the perineal body lie and what is its function?

Back 32

lies at centrepoint of perineum between urogenital and anal triangles, close to skin

it is the central stabilising structure in perineum

Front 33

How to pelvic viscera prolapse?

Back 33

muscles weaken or nerve gets damaged, which places stress/tension on ligaments. The ligaments then stretch and stop supporting the viscera.

More common in females due to childbirth, wider opening and muscle weakening during menopause

Front 34

What supplies pelvic viscera?

Back 34

internal iliac artery

Front 35

What supplies perineal structures?

Back 35

internal pudendal artery (a branch of int iliac artery)

Front 36

What vein drains deep dorsal vein of penis/clitoris?

Back 36

valveless venous plexus- by travelling under pubic symphysis through hole of pelvic membrane

Front 37

From where do lymphatics drain to superficial inguinal nodes?

Back 37

below umbilicus

Front 38

Describe the sympathetic innervation of pelvic and perineal viscera from aorta?

Back 38

aortic plexus --> superior hypograstric plexus --> bifurcates to hypogastric nerves

Front 39

What is the name of the mixed sympathetic and parasympathetic plexus of pelvis?

Back 39

inferior hypogastric plexus

Front 40

What is the effect of nerve damage when surgically removing prostate?

Back 40

damage parasympathetics to erectile tissue of penis from inferior hypogastric plexus

Front 41

what nerves supply erectile tissue in males?

Back 41

cavernous nerves (because they supply cavernous tissue)

Front 42

What is the somatic nerve to perineum and what does it innervate?

Back 42

pudendal nerve (S2-4) - innervates skin and voluntary muscle control of micturition

Front 43

Where do sympathetic pain efferents travel from perineal viscera?

Back 43

T1-L2 spinal level (hence can have pain sensation at T1-L2 dermatomes)

Front 44

What is the pelvic pain line?

Back 44

At level of halfway along sigmoid colon - anything above is sympathetic to T1-L2, anything below is parasymp to S2-S4

Front 45

What is the nerve innervation to the scrotum?

Back 45

Ant 2/3 scrotum = pudenedal nerve (S3)
Post 1/3 scrotum = L1 (ilioinguinal, and genital br of genitofemoral)