2. Anatomy of the Pelvis

Question 1

Label A-E of the pelvis.

Answer 1

A: greater (false) pelvis

B: lesser (true) pelvis

C: pelvic brim/inlet (divides the greater and lesser pelvis)

D: pelvic outlet

E: perineum

Question 2

Label A-G of the pelvis.

Answer 2

A: iliac crest

B: PSIS

C: ASIS

D: ischial spine

E: ischial tuberosity

F: pubic tubercle

G: superior pubic ramus

Question 3

Label A and B and state what they form.

Answer 3

A: arcuate line

B: pectineal line

Form the pelvic brim

Question 4

List the ligaments of the pelvis.

What 2 structures does the inguinal ligament go between?

How is the sacrum rotated?

What do the pelvic ligaments do?

What nerve goes through the greater sciatic foramen?

Answer 4

Sacrotuberous, sacrospinous, sacroiliac. Symphysis pubis is a secondary cartilaginous joint that unites articular surfaces.

Pubic tubercle and ASIS

Body weight transmitted through the spine rotates the sacrum forwards

Sacrospinous and sacrotuberous ligaments prevent the lower end of the sacrum being rotated upward at the sacroiliac joint. They stabilise the pelvis. They also convert the sciatic notch into the greater and lesser sciatic foramina.

Sciatic

Question 5

Label A-E

Answer 5

A: sacrospinous ligament

B: sacrotuberous ligament

C: obturator canal

D: obturator membrane

E: greater and lesser sciatic foramen

Question 6

Label A-C

Answer 6

A: sacroiliac

B: sacrospinous

C: sacrotuberous

Question 7

Label A-E

Answer 7

A: anterior sacroiliac ligament

B: sacrospinous

C: sacrotuberous

D: pectineal line

E: pubic symphysis

Question 8

How does the female pelvis differ from the male?

Answer 8

Adapted for childbirth. Shallower, wider, smoother. Pelvic cavity larger and cylindrical. Pubic arch wider (b/c ischial tuberositites further apart). Pelvic outlet larger. Pelvic inlet similar. Pregnancy hormones allow stretching of ligaments and increase movement - 10% increase in transverse diameter. Not as ideal for locomotion, wider acetabular so femur less directly over knees.

Question 9

Label A and B.

What runs from the sacral promontry to the symphysis pubis?

Answer 9

A: pelvic inlet

B: pelvic outlet

Diagonal conjugate.

Question 10

What structures make up the three pelvic walls:

a) anterior wall
b) posterior wall
c) lateral walls

Answer 10

a) pubic rami and symphysis
b) sacrum, coccyx and piriformis
c) hip bone below pelvic inlet, obturator membrane, sacrospinous and sacrotuberous ligaments, obturator internus muscle

Question 11

Label A-C

Answer 11

A: sacroiliac

B: sacrospinous

C: sacrotuberous

Question 12

Label A-C

Answer 12

A: piriformis (leaves pelvis through greater sciatic foramen)

B: coccygeus (overlying sacrospinous ligament)

C: obturator internus (leaves pelvis through lesser sciatic foramen)

Question 13

What is above and below the pelvic floor?

What forms the pelvic floor (diaphragm)?

Is the pelvic floor complete?

Answer 13

Above: main pelvic cavity. Below: perineum

Levator ani muscles, coccygeus muscles and their covering fascia.

No - incomplete anteriorly (urethra and vagina in females)

Question 14

Label A-C.

What does the green line indicate?

Answer 14

A: levator ani

B: coccygeus

C: piriformis

Levator ani muscle attachment

Question 15

Label A and B

Answer 15

A: obturator nerve

B: pudendal nerve (goes to perineum behind the pelvic floor)

Question 16

The levator ani (pelvic floor) is divided into what 4 parts? Describe them.

Answer 16

1) levator prostate/ sphincter vaginae: forms sling around prostate/vagina and inserts into the perineal body (support prostate/constrict vagina)
2) puborectalis: sling from pubic bone around rectoanal junction
3) pubococcygeus: pubis to anococcygeal body (fibrous mass between tip of coccyx and anal canal)
4) iliococcygeus: ilium to anococcygeal body and coccyx

JOIN TOGETEHR IN MIDDLE AT MIDLINE (LEVATOR) RAPHE

Question 17

Label A-H of this male pelvic floor.

Answer 17

A: levator prostatae

B: puborectalis

C: pubococcygeus

D: iliococcygeus

E: levator ani

F: coccygeus

G: midline raphe

H: piriformis

Question 18

Label A-D of this female pelvic floor.

Answer 18

A: puborectalis and pubococcygeus

B: iliococcygeus

C: coccygeus

D: piriformis

Question 19

Label A-C

Answer 19

A: iliococcygeus

B: pubococcygeus

C: puborectalis

Question 20

What does the levator ani do?

How might the pelvic floor get injured, and what might pelvic floor injury cause?

Answer 20

Supports and maintains pelvic viscera in position. Resists intrapelvic pressure and expulsive efforts of abdominal muscles. Assists sphincter urethrae (EUS). Important sphincter action on the ano-rectal junction (also sphincter of the vagina). Helps support vertebral column.

Difficult childbirth - levator ani muscles fail to recoil and take up previous position. Causes: uterine and vaginal prolapse, herniation of bladder (cytocele), alteration of position of bladder neck - stress incontinence, prolapse of rectum.

Question 21

What does puborectalis do?

Compare fractures of the false and true pelvis.

What are some complications of pelvic fractures?

Answer 21

Maintains anal angle at the anorectal junction which is important for anal continence. Retracts the mucous membrane of the lower anal canal. [PIC]

False: rare. True: rigid ring - one break, no displacement. Pelvic injuries normally when pressure from both sides e.g. jumping from high building.

Pelvic veins = massive hemorrhage. Male urethra - esp in vertical fractures disrupting the urogenital diaphragm. Bladder (behind pubis). Rectum rarely damaged (in sacrum concavity). Nerve injuries follow sacral fractures.