Muscles Of The Thorax, Abdomen, And Pelvis

Front 1

External abdominal oblique

Back 1

Origin: ribs 5-12
Insertion: linea alba, iliaccrest, pubis
Action: compresses abdominal wall, laterally rotates trunk

Front 2

Internal abdominal oblique

Back 2

Origin: inguinal ligament, iliaccrest
Insertion: linea alba, ribs 10-12
Action: compresses abdominal wall, laterally rotates trunk

Front 3

Transversus abdominis

Back 3

Origin: inguinal ligament, iliac crest, ribs 7-12
Insertion: linea alba, crest of pubis
Action: compresses abdominal wall, laterally rotates trunk

Front 4

Rectus abdominis

Back 4

Origin: crest of pubis, symphysis pubis
Insertion: cartilages of ribs 5-7, xiphoid process
Action: flexes vertebral column, compresses abdominal wall

Front 5

Serratus anterior

Back 5

Origin: ribs 1-8
Insertion: vertebral border and inferior angle of scapula
Action: abducts scapula, rotates scapula to elevate shoulder

Front 6

External intercostals

Back 6

Origin: inferior border of a rib
Insertion: superior border of rib below
Action: elevates ribs (increases volume in thorax)

Front 7

Internal intercostals

Back 7

Origin: inferior border of a rib
Insertion: superior border of rib below
Action: depresses ribs (decreases volume in thorax)

Front 8

Diaphragm

Back 8

Origin: xiphoid process, lower ribs, upper lumbar vertebrae
Insertion: central tendon
Action: inspiration (contraction), expiration (relaxation)