Muscles Acting on Vertebral Column and Muscles of the Thorax

Vocabulary flashcards covering the origin, insertion, and action of muscles acting on the vertebral column (erector spinae group and quadratus lumborum) and muscles of the thorax (diaphragm and intercostal muscles).

Erector spinae

Origin: Sacrum, ilium, and lumbar vertebrae

Insertion: Ribs, cervical vertebrae, and skull

Action:  Extends the vertebral column (allows the spine to extend)

Iliocostalis

Origin: Sacrum, ilium, and lumbar vertebrae (goes very far inferior, sends cool slits)

Insertion:  Ribs and cervical vertebrae

Action: Extends and laterally flexes the vertebral column (runs from supramedial to infralateral; side bending; most lateral erector spinae)

Longissimus

Origin: Sacrum and ilium

Insertion: Ribs, vertebrae, and skull

Action:  Extends and laterally flexes the vertebral column and head (side bending; intermediate erector spinae)

Spinalis

Origin: Spinous processes of lower vertebrae

Insertion:  Spinous processes of upper vertebrae

Action:  Extends the vertebral column (most medial erector spinae)

Quadratus lumborum

Origin: iliac crest and lower lumbar vertebrae

Insertion:  Twelfth rib and upper lumbar vertebrae

Action:  Laterally flexes the vertebral column (side bend) and depresses the twelfth rib

Diaphragm

Origin: Interior of ribs, sternum, and lumbar vertebrae

Insertion:  Central tendon of the diaphragm

Action:  Depresses the floor of the thorax during inspiration

External intercostal

Origin: Inferior margin of each rib

Insertion:  Superior border of next rib below

Action:  Elevates the ribs during quiet inspiration (fiber orientation runs from supralateral to inframedial)

Internal intercostals

Origin: Superior margin of each rib

Insertion:  Inferior border of next rib above

Action:  Depresses the ribs during forced expiration (fiber orientation runs from supramedial to infralateral)