Muscles of the Vertebral Column, Abdominal Wall, & Pelvic Floor

quadratus lumborum (origin)

iliac crest

quadratus lumborum (insertion)

transverse processes of L1-L4 and rib 12

quadratus lumborum (action)

extends vertebral column; lateral flexion when unilateral contractions occur

quadratus lumborum (innervation)

anterior rami of spinal nerves T12-L4

external oblique (origin)

anterior surfaces of ribs 5-12

external oblique (insertion)

anterior iliac crest and linea alba by aponeurosis

external oblique (action)

tenses abdominal wall; compresses abdominal contents; aids in trunk rotation

external oblique (innervation)

anterior rami of spinal nerves T7-T12

internal oblique (origin)

iliac crest and inguinal ligament

internal oblique (insertion)

costal cartilages of lower ribs, linea alba, and pubic crest

internal oblique (action)

tenses abdominal wall; compresses abdominal contents; aids in trunk rotation

internal oblique (innervation)

anterior rami of spinal nerves T7-L1

transversus abdominis (origin)

costal cartilages of lower ribs, iliac crest, and inguinal ligament

transversus abdominis (insertion)

linea alba and pubic crest

transversus abdominis (action)

compresses abdominal contents

transversus abdominis (innervation)

anterior rami of spinal nerves T7-L1

rectus abdominis (origin)

pubic crest and pubic symphysis

rectus abdominis (insertion)

xiphoid process of sternum and costal cartilages of ribs 5-7

rectus abdominis (action)

flexes vertebral column; compresses abdominal contents

rectus abdominis (innervation)

anterior rami of spinal nerves T6-T12

diaphragm (origin)

costal cartilages and ribs 7-12, xiphoid process of sternum, and lumbar vertebrae

diaphragm (insertion)

central tendon of diaphragm

diaphragm (action)

flattens during contraction, which expands thoracic cavity and compresses abdominal viscera during inspiration

diaphragm (innervation)

phrenic nerves

external intercostals (origin)

inferior border of superior rib

external intercostals (insertion)

superior border of inferior rib

external intercostals (action)

elevates ribs, which expands thoracic cavity during inspiration

external intercostals (innervation)

intercostal nerves

internal intercostals (origin)

superior border of inferior rib

internal intercostals (insertion)

inferior border of superior rib

internal intercostals (action)

depresses ribs, which compresses thoracic cavity during forced expiration

internal intercostals (innervation)

intercostal nerves

linea alba (identify)

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psoas major (origin)

intervertebral discs, bodies, and transverse processes of T12-L5

psoas major (insertion)

lesser trochanter of femur

psoas major (action)

flexes thigh at hip; flexes trunk at hip when thigh is fixed

psoas major (innervation)

anterior rami of lumbar spinal nerves

iliacus (origin)

iliac fossa of ilium

iliacus (insertion)

lesser trochanter of femur

iliacus (action)

flexes thigh at hip; flexes trunk at hip when thigh is fixed

iliacus (innervation)

femoral nerve