Rectus thoracis muscle

The rectus thoracis muscle is a thin, strap-like musclethat lies on the ventrolateral thoracic wall, extending from the first rib to the cartilage of the fourth rib, situated deep to the cutaneous trunci and external intercostal muscles.

Origin: First rib, opposite the most ventral portion of the scalenus muscle.

Insertion: Ventral ends of the second through fourth ribs.

Action: Inspiration.

Nerve: Lateral branch of the intercostales.