Thorax Muscles

Question 1

Diaphragm

Answer 1

Origin: xiphoid process, costal margin, fascia over the quadratus lumborum and psoas major mm.(lateral & medial arcuate ligaments), vertebral bodies L1-L3
Insertion: central tendon of the diaphragm
Action: pushes the abdominal viscera inferiorly, increasing the volume of the thoracic cavity (inspiration)

Question 2

external intercostal

Answer 2

Origin: lower border of a rib within an intercostal space
Insertion: upper border of the rib below, coursing, downward and medially
Action: keeps the intercostal space from blowing out or sucking in during respiration

Question 3

innermost intercostal

Answer 3

Origin: upper boarder of ribs
Insertion: fibers course up and medially to insert on the inferior margin of the rib above
Action: keeps the intercostal space from blowing out or sucking in during respiration

Question 4

internal intercostal

Answer 4

Origin: upper border of a rip
Insertion: lower border of rib above, coursing up and medially
Action: keeps the intercostal space from blowing out or sucking in during respiration

Question 5

Levatores costarum

Answer 5

Origin: transverse processes C7-T11
Insertion: rib below its origin, medial to the angle
Action: Elevates the ribs

Question 6

Subcostalis

Answer 6

Origin: angle of the ribs
Insertion: angle of a rib 2-3 ribs above origin
Action: compresses the intercostal spaces

Question 7

Transverse Thoracis

Answer 7

Origin: posterior surface of the sternum
Insertion: inner surfaces of costal cartilages 2-6
Action: compresses the thorax for forced expiration