Posterior Abdominal Wall and Pelvic Floor (Trail Guide)

Question 1

Diaphragm

Answer 1

A: Draw down the central tendon of the diaphragm;
Increase the volume of the thoracic cavity during inhalation

O: Costal attachment - Inner surface of lower six ribs
Lumbar attachment - Upper two or three lumbar vertebrae
Sternal attachment - Inner part of xiphoid

I: Central tendon

N: Phrenic C3-C5

Question 2

Psoas Major

Answer 2

A: (With the origin fixed)
Flex hip (coxal joint); May laterally rotate the hip (coxal joint)
(With the insertion fixed)
Flex the trunk toward the thigh; Tilt pelvis anteriorly
(Unilaterally)
Assist to laterally flex the lumbar spine

O: Bodies and transverse processes of lumbar vertebrae

I: Lesser trochanter

N: Lumbar plexus L1-4

Question 3

Iliacus

Answer 3

A: (With the origin fixed)
Flex hip (coxal joint); May laterally rotate the hip (coxal joint)
(With the insertion fixed)
Flex the trunk toward the thigh; Tilt pelvis anteriorly

O: Iliac fossa

I: Lesser trochanter

N: Femoral nerve (L2-L3)

Question 4

Quadratus Lumborum

Answer 4

A: (Unilaterally)
Laterally tilt (elevate) the pelvis); Laterally flex the vertebral column to the same side
(Bilaterally)
Fix the last rib during forced inhalation and exhalation; Assist to extend the vertebral column

O: Posterior iliac crest

I: Last rib and transverse processes of L1-L4)

N: Lumbar plexus (T12-L3)

Question 5

Levator Ani

Answer 5

O: Body of pubis, tendinous arch of obturator fascia, ischial spine

I: Perineal body, coccyx, anococcygeal ligament, walls of prostate or vagina, rectum and anal canal

N: Nerve to Levator Ani (S3-S4)

A: Forms most of the pelvic diaphragm that support pelvic viscera and resist increases to intra-abdominal pressure

Question 6

Ischiococcygeus

Answer 6

O: Ischial Spine

I: Inferior end of sacrum and coccyx

N: Branches of S4-S5

A: Forms a small part of pelvic diaphragm that supports viscera, flexes coccyx

Question 7

Floor of Pelvic Cavity

Answer 7

3 muscles:
- Puborectalis
- Pubococcygeus
- Iliococcygeus

Question 8

Obturator Internus

Answer 8

A: Laterally rotate the hip (Coxal joint)

O: Obturator membrane and inferior surface of obturator forament

I: Medial surface of greater trochanter

N: Sacral Plexus L5-S2

Question 9

Piriformis

Answer 9

A: Laterally rotate the hip (coxal joint); Abduct the hip when flexed

O: Anterior surface of sacrum

I: Superior aspect of greater trochanter

N: Sacral Plexus L5-S2