Muscles of the Abdomen

Question 1

Cremaster

Answer 1

attachment- from the medial edge of the internal oblique to spermatic cord

actions- elevation of testis

innervation- genitofemoral nerve

Question 2

Diaphragm

Answer 2

attachments- from xiphoid process, inner surface of the lower ribs & costal cartilages, medial & lateral arcuate ligaments & lumbar vertebrae via the crura to the central tendon

actions- inspiration (negative thoracic pressure by inferior displacement)

innervation- phrenic nerve C3-5

Question 3

External abdominal oblique (anterior & lateral fibers)

Answer 3

attachments- from lower 8 ribs to iliac crest & rectus sheath; middle layer TL fascia

actions- lateral flexion & rotation of the trunk, & compression of the abdominal cavity

innervation- ventral rami T7-12

Question 4

Internal abdominal oblique (lower anterior, upper anterior, & lateral fibers)

Answer 4

attachments- from thoracolumbar fascia to inguinal ligament, iliac crest & rectus sheath

actions- lateral flexion & rotation of the trunk, & compression of the abdominal cavity

innervation- lower thoracic & L1 ventral rami T7-12, L1, iliohypogastric and ilioinguinal, ventral rami

Question 5

Quadratus lumborum

Answer 5

attachments- from 12th rib & transverse processes of L1-4 to iliolumbar ligament & iliac crest

actions- extension & lateral flexion of the trunk, and fixes 12th rib during respiration

innervation- Lumbar plexus ventral rami T12-L3

Question 6

Rectus abdominis

Answer 6

attachments- from xiphoid process & adjacent costal cartilages of ribs 5-7 to pubic crest & tubercle (symphysis)

actions- flexion of trunk & compression of abdominal cavity

innervation- lower thoracic ventral rami T5-12

Question 7

Transversus abdominis

Answer 7

attachments- from lower six costal cartilages & thoracolumbar fascia to inguinal ligament, iliac crest & rectus sheath

actions- compression of the abdominal cavity

innervation- lower thoracic T7-12, ventral divisions