The fibers course anteriorly and inferiorly ("hands in pocket"). External intercostal membrane replaces them in the region of the costal cartilages.

Stabilize ribs and thoracic cage during inspiration and expiration and elevate and depress the ribs during forced respiratory movements.

Innervated by anterior intercostal nerves.

Course at right angles to those

of the external. They begin at the lateral

margin of the sternum.

Same functions and innervation as external.

The most anterior of

these, the

transversus thoracis muscles

are deep to and cover part of, the internal

thoracic artery.

Supply blood to chest wall.

Branch of subclavian artery.

Run lateral to margin of sternum.

Gives off 6 anterior intercostal arteries before dividing into two terminal branches: Superior epigastric and musculophrenic.

Run along underneath ribs.

Can form functional and anastomotic connections with Posterior intercostal arteries.

There are 6 that come off the internal thoracic artery

AKA - ventral ramus of T1-T11 spinal nerves.

Supply both motor and sensory fibers to muscles and skin of chest wall.

Sensory fibers parietal pleura lining inside of chest cavity.

And postganglionic sympathetic fibers to lateral and anterior cutaneous branches.

Active during inspiration and elevate the ribs and prevent intercostal spaces from bulging out or being drawn in.

Innervated by intercostal nerves.

11 intercostal muscles

Interconnect the costal cartilages.

Innervated by intercostal nerves.

Perpendicular to external intercostal muscles.