Muscles of the Thoracic Wall Flashcards
What direction do the internal intercostal muscles fibers run?
Inferoposteriorly
What direction do the external intercostal muscle fibers run?
Inferoanteriorly
Intercostal muscles and membrane
Start as muscles medially and then end up as membrane more lateral
External intercostals and membrane
Start as muscles laterally and then end as membrane more medially
Innermost intercostals and membrane
Sit laterally as muscles and do not contain a membrane
External intercostal
Origin: inferior border of the rib
Insertion: superior border of the rib below
Innervation: intercostal nerve
Action: during forced inspiration - elevates ribs
Internal intercostal
Origin: inferior border of the rib
Insertion: superior border of the rib below
Innervation: intercostal nerve
Action: during forced inspiration - interosseous part depresses rib and interchondral part elevates rib
Innermost intercostal
Origin: inferior border of the rib
Insertion: superior border of the rib below
Innervation: intercostal nerve
Action: during forced inspiration - interosseous part depresses rib and interchondral part elevates rib
Transverse thoracis
Origin: posterior surface of the lower sternum
Insertion: internal surface of costal cartilages of 2-6
Innervation: none
Action: weakly depresses ribs
Subcostal
Origin: internal surface of lower ribs near their angles
Insertion: superior border of 2-3 ribs below
Innervation: none
Action: same as internal intercostal
Levatores costarum
Origin: transverse processes of C7-T11
Insertion: subjacent ribs between their angles and tubercles
Innervation: posterior rami of C8-T11 nerves
Action: elevates ribs
External oblique
Origin: external surfaces of ribs 5-12
Insertion: anterior half of iliac crest, pubic tubercle, and linea alba
Innervation: thoracoabdominal nerve (anterior rami of C7-T11) and subcostal nerve
Action: compresses/supports abdominal viscera and flexes and rotates the trunk
Internal oblique
Origin: thoracocolumbar fascia, connective tissue deep to inguinal ligament, anterior 2/3 of iliac crest
Insertion: inferior borders of ribs 10-12, linea alba, pubis via conjoint tendon
Innervation: thoracoabdominal nerve (anterior rami of C7-T11) and first lumbar nerve
Action: compresses/supports abdominal viscera and flexes and rotates the trunk
Transverse oblique
Origin: connective tissue deep to inguinal ligament, thoracocolumbar fascia, iliac crest, and internal surfaces of 7-12th costal cartilages
Insertion: linea alba w/ aponeurosis of internal oblique, pubic crest, and pectin pubis via conjoint tendon
Innervation: thoracoabdominal nerve (anterior rami of C7-T11) and first lumbar nerve
Action: compresses/supports the abdominal viscera
Rectus abdominis
Origin: pubic symphysis and pubic crest
Insertion: xiphoid process and 5-7th costal cartilages
Innervation: thoracoabdominal nerve (anterior rami of inferior six thoracic nerves)
Action: flexes trunk (lumbar vertebrae), compresses abdominal viscera, and stabilizes/controls tilt of pelvis
