Deep Muscles of the Thorax

Question 1

What muscles pull ribs toward one another to elevate the ribcage? (Synergists of diaphragm)

Answer 1

External intercostals, originating from the inferior border of one rib to the superior border of rib below.
Fibers run obliquely (down and forward).

Question 2

What muscles pull the ribs together and depress ribcage, aiding in forced expiration? (Antagonists if external intercostals)

Answer 2

Internal intercostals, originating from superior border of one rib to costal groove of the rib above it.
Fibers run deep to external intercostals (upward and anterior)

Question 3

What muscle is the prime mover of inspiration and flattens on contraction?

Answer 3

Diaphragm, with foramen for aorta, inferior vena cava, and esophagus, fibers insert into boomerang-shapes central tendon.
O- inferior, internal surface of ribcage & sternum, costal cartilages of T6-T12 ribs and lumbar vertebrae.

Question 4

What nerve innervates the diaphragm?

Answer 4

Phrenic nerves

Question 5

What nerve innervates the intercostals?

Answer 5

Intercostal nerves