Abdomen and Thorax Muscles

Intercostal muscles

External, internal, and innermost intercostal

External intercostal muscle

Internal Intercostal muscle

Innermost Intercostal muscle

Intercostal muscle Origin

Inferior surface of upper rib

Intercostal muscle Insertion

Superior surface of lower rib

Intercostal muscle Innervation

Intercostal nerve

Intercostal muscle Action

Inspiration/expiration

Anterior abdominal wall muscles

rectus abdominis, external oblique, internal oblique, transversus abdominis

External Oblique

External Oblique Origin

Lateral aspect of lower 8 ribs

External Oblique Insertion

Linea alba, pubic tubercle, iliac crest

External Oblique Innervation

Lower 6 thoracis nerves, iliohypogastric and ilioinguinal nerves

External Oblique Action

Trunk flexion, side bending, rotation towards opposite side, compression of abdominal contents

Internal Oblique

Internal Oblique Origin

Thoracolumbar fascia, iliac crest, and inguinal ligament

Internal Oblique Insertion

Costal cartilage of ribs 7-10 and linea alba

Internal Oblique Innervation

Lower 6 thoracic nerves, iliohypogastric and ilioinguinal nerves

Internal Oblique Action

Trunk flexion, side bending, rotation towards same side, compression of abdominal contents

Transverse abdominis

Transverse abdominis Origin

Costal cartilage of lower 6 ribs, thoracolumbar fascia, iliac crest, and inguinal ligament

Transverse abdominis Insertion

Linea alba

Transverse abdominis Innervation

Lower 6 thoracic nerves, iliohypogastric and ilioinguinal

nerves

Transverse abdominis Action

Compression of abdominal contents

Rectus abdominis

Rectus abdominis Origin

Pubic symphysis

Rectus abdominis Insertion

Costal cartilage of ribs 5,6, and 7 and xiphoid process

Rectus abdominis Innervation

Lower 6 thoracic nerves

Rectus abdominis Action

Trunk flexion

Posterior Abdominal Wall

Psoas major

Iliacus

Quadratus Lumborum

Thoracoabdominal diaphragm

Psoas Major

Psoas Major Origin

Transverse processes, side of the vertebral bodies, and intervertebral discs of all lumbar vertebrae

Psoas Major Insertion

Lesser trochanter of the femur

Psoas Major Innervation

Lumbar nerves (L1-3)

Psoas Major Action

Felxion of thigh

Iliacus

Iliacus Origin

Iliac fossa

Iliacus Insertion

Leser trochanter of femur

Iliacus Innervation

Femoral Nerve

Iliacus Action

Flexion of thigh

Quadratus lumborum

Quadratus lumborum Origin

Posterior iliac crest and transverse processes of lower lumbar vertebrae

Quadratus lumborum Insertion

12th rib and tranverse processes of upper lumbar vertebrae

Quadratus lumborum Innervation

T12 (subcostal n.) and lumbar nerves (L1-4)

Quadratus lumborum Action

Lumbar extension and side bending

Thoracoabdominal diaphragm

Thoracoabdominal diaphragm Origin

Sternal: posterior xiphoid process

Costal: internal surface of lower ribs and costal cartilage

Vertebral: right and left crura and upper lumbar vertebrae

Thoracoabdominal diaphragm Insertion

Thoracoabdominal diaphragm Innervation

Phrenic (C3-5)

Thoracoabdominal diaphragm Action

Depression of dome causing inspiration

Pelvic diaphragm muscles

levator ani coccygeus

Orbuartor internus

Piriformis

Levator ani

Levaor Ani Muscles

Pubococcygeus

Puborectalis

Iliococcygeus

Levator Ani

Posterior pubic bone, across tendinous arch to ischial spine

Levator Ani Insertion

Superior surface of perineal membrane in the midline at perineal body, sides of anal canal and anococcygeal ligament

Levator Ani Innervation

Ventral Ramus S4 Pudendal nerve

Levator Ani Actions

Supports pelvic viscera, maintains anorectal angle, reinforces external anal sphicters

Coccygeus

(ischiococcygeus)

Coccygeus Origin

ischial spine and sacrospinous ligament

Coccygeus Insertion

Lateral coccyx, sacral border

Coccygeus Innervation

Ventral rami S2 and S3

Coccygeus Action

supports pelvic viscera, pulls coccyx forward after defecation