Abdominal Muscles

Question 1

Answer 1

RECTUS ABDOMINIS

ORIGIN

Pubic symphysis of the pelvis

INSERTION

Ribs 5–7

ISOLATED FUNCTION

Concentric Action

Spinal flexion, lateral flexion, and rotation

INTEGRATED FUNCTION

Eccentric Action

Spinal extension, lateral flexion, and rotation

Isometric Action

Stabilizes the lumbo-pelvic-hip complex

INNERVATION

Intercostal nerve T7–T12

Question 2

Answer 2

EXTERNAL OBLIQUE

ORIGIN

External surface of ribs 4–12

INSERTION

Anterior iliac crest of the pelvis, linea alba, and contralateral rectus sheaths

ISOLATED FUNCTION

Concentric Action

Spinal flexion, lateral flexion, and contralateral rotation

INTEGRATED FUNCTION

Eccentric Action

Spinal extension, lateral flexion, and rotation

Isometric Action

Stabilizes the lumbo-pelvic-hip complex

INNERVATION

Intercostal nerves (T8–T12), iliohypogastric (L1), and ilioinguinal (L1)

Question 3

Answer 3

INTERNAL OBLIQUE

ORIGIN

Anterior two-thirds of the iliac crest of the pelvis and thoracolumbar fascia

INSERTION

Ribs 9–12, linea alba, and contralateral rectus sheaths

ISOLATED FUNCTION

Concentric Action

Spinal flexion (bilateral), lateral flexion, and ipsilateral rotation

INTEGRATED FUNCTION

Eccentric Action

Spinal extension, rotation, and lateral flexion

Isometric Action

Stabilizes the lumbo-pelvic-hip complex

INNERVATION

Intercostal nerves (T8–T12), iliohypogastric (L1), and ilioinguinal (L1)

Question 4

Answer 4

TRANSVERSE ABDOMINIS

ORIGIN

Ribs 7–12, anterior two-thirds of the iliac crest of the pelvis, and thoracolumbar fascia

INSERTION

Linea alba and contralateral rectus sheaths

ISOLATED FUNCTION

Concentric Action

Increases intra-abdominal pressure and supports the abdominal viscera

INTEGRATED FUNCTION

Isometric Action

Synergistically with the internal oblique, multifidus, and deep erector spinae to stabilize the lumbo-pelvic-hip complex

INNERVATION

Intercostal nerves (T7–T12), iliohypogastric (L1), and ilioinguinal (L1)

Question 5

Answer 5

DIAPHRAGM

ORIGIN

Costal part: Inner surfaces of the cartilages and adjacent bony regions of ribs 6–12
Sternal part: Posterior side of the xiphoid process
Crural (lumbar) part: (1) Two aponeurotic arches covering the external surfaces of the quadratus lumborum and psoas major and (2) right and left crus, originating from the bodies of L1–L3 and their intervertebral discs

INSERTION

Central tendon

ISOLATED FUNCTION

Concentric Action

Pulls the central tendon inferiorly, increasing the volume in the thoracic cavity

INTEGRATED FUNCTION

Isometric Action

Stabilization of the lumbo-pelvic-hip complex

INNERVATION

Phrenic nerve (C3–C5)