Myology of the abdominals

Question 1

Origin of external oblique?

Answer 1

Outer borders of the lower 8 ribs and their costal cartilages

Question 2

Insertion of external oblique?

Answer 2

Anterior 2/3’s of the outer lip of the iliac crest and Linea alba

Question 3

Action of external oblique?

Answer 3

Bilaterally compresses abdomen and flexes vertebral column, unilaterally laterally flexes the vertebral column (especially lumbar), and rotates vertebral column.

Question 4

Innervation of external oblique?

Answer 4

Thoracic spinal nerves T7-T12 and the iliohypogastric nerve

Question 5

Origin of internal oblique?

Answer 5

Lateral 2/3’s of the inguinal ligament, anterior 2/3’s of the iliac crest, thoracolumbar fascia

Question 6

Insertion of internal oblique?

Answer 6

Inferior border of the lower 4 ribs, and forms a aponeurosis attaching into the linea alba

Question 7

Action of internal oblique?

Answer 7

Bilaterally flexes the vertebral column and compresses abdomen, unilaterally laterally flexes vertebral column and rotates vertebral column (trunk).

Question 8

Innervation of internal oblique?

Answer 8

Thoracic spinal nerves T8-T12, iliohypogastric nerve, and ilioinguinal nerve

Question 9

Origin of transversus abdominis?

Answer 9

Lateral 1/3 of the inguinal ligament, anterior 2/3’s of the iliac crest, thoracolumbar fascia, inner surface of lower 6 ribs and their costal cartilages

Question 10

Insertion of transversus abdominis?

Answer 10

Linea alba

Question 11

Action of transversus abdominis?

Answer 11

Compresses abdomen

Question 12

Innervation of transversus abdominis?

Answer 12

Thoracic spinal nerves T8-T12, iliiohypogastric nerve, and ilioinguinal nerve

Question 13

Origin of quadratus lumborum?

Answer 13

Iliolumbar ligament, adjacent iliac crest

Question 14

Insertion of quadratus lumborum?

Answer 14

Medial half of the 12th rib, transverse processes of lumbar vertebrae

Question 15

Action of quadratus lumborum?

Answer 15

Unilaterally side flexes trunk, unilaterally (reverse O/I) prevents pelvis dropping on non-standing leg when on one leg
Bilaterally extends trunk
Bilaterally pulls 12th ribs inferiorly during forced exhalation, fixes 12th ribs to prevent their elevation during deep inhalation

Question 16

Innervation of quadratus lumborum?

Answer 16

Thoracic spinal nerves T12-L4 and subcostal nerve

Question 17

Origin of rectus abdominis?

Answer 17

Front of pubic symphysis and pubic crest

Question 18

Insertion of rectus abdominis?

Answer 18

Xiphoid process, costal cartilages of 5th, 6th, and 7th ribs

Question 19

Action of rectus abdominis?

Answer 19

Trunk flexion, R O/I allows for pelvic tilt, unilateral trunk side flexion (same side)

Also involved in the sneeze and coughing reflex, rectus abdominis can increase intra-abdominal pressure to force the diaphragm upwards during expulsion

Question 20

Innervation of rectus abdominis?

Answer 20

Thoracoabdominal nerve (T7-T12)