Trunk Muscles

Question 0

Internal intercostals

Answer 0

O: lower border of rib (11 pairs)
I: upper border of rib below origin
A: maintain intercostal space; variable reports on involvement in inspiration and expiration
Inn: intercostal nerves

Question 1

External intercostals

Answer 1

O: lower border of rib (11 pairs)
I: upper border of rib below origin
A: maintain intercostal space; variable reports of involvement in inspiration and expiration
Inn: intercostal nerves

Question 2

Diaphragm

Answer 2

O: inner surface of xiphoid process; lower ribs anteriorly and posteriorly; bodies do upper lumbar vertebrae as crura of diaphragm; fascia over psoas major and quadratic lumborum
I: central tendon of diaphragm
A: depression of central tendon to increase cervical dimension of thoracic cavity
Inn: phrenic n (C345)

Question 3

External oblique

Answer 3

O: lower six ribs
I: anterior part of iliac crest; pubis; aponeurosis into linea alba
A: with IO and TA, compression of abdominal cavity; flexion and rotation of trunk
Inn: lower intercostal n

Question 4

Internal oblique

Answer 4

O: iliopsoas fascia and lateral half of inguinal ligament; anterior part of iliac crest; thoracolumbar fascia
I: aponeurosis of kinda alba
A: compression of abdominal cavity
Inn: lower intercostal nerves; L1 through it’s iliohypogastric and ilioinguinal branches

Question 5

Transverse abdominus

Answer 5

O: thoracolumbar fascia; lateral part of inguinal ligament; tips of lower six ribs; anterior part of iliac crest
I: aponeurosis into linea alba
A: compression of abdominal cavity
Inn: lower intercostal nerves; L1 through it’s iliohypogastric and ilioinguinal branches

Question 6

Rectus abdominus

Answer 6

O: pubic crest; ligaments of pubic symphysis
I: xiphoid process; ribs 5-7
A: flexion of trunk
Inn: lower intercostal nerves

Question 7

Quadratus lumborum

Answer 7

O: medial part of iliac crest
I: rib 12; lower lumbar vertebrae
A: lateral flexion of vertebral column; fixation of last rib to form stable base for contraction of diaphragm
Inn: branches from T12 and L1-L3

Question 8

Levator ani

Answer 8

O: pubis; ischial spine; fascia between these bony origins
I: coccyx; midline around pelvic organs and with muscle of opposite side
A: support of pelvic viscera, particularly during increased abdominal pressure; pulls anal canal upward
Inn: branches from S3 and S4

Question 9

Ischiococcygeus

Answer 9

O: ischial spine
I: lower sacrum; upper coccyx
A: pulling coccyx anteriorly; support of pelvic viscera
Inn: branches from S4 and S5