Transversus thoracis muscle

Transversus thoracis muscle
Posterior surface of sternum and costal cartilages, showing transversus thoracis.
Details
Origin	Costal cartilages of last 3-4 true ribs, body of sternum and xiphoid process
Insertion	Ribs/costal cartilages 2-6
Artery	Intercostal arteries
Nerve	Intercostal nerves
Actions	Depresses ribs
Identifiers
Latin	Musculus transversus thoracis
Dorlands /Elsevier	m_22/12551274
TA	A04.4.01.016
FMA	9760
Anatomical terms of muscle []

The transversus thoracis muscle (/trænzˈvɜːrsəs θəˈreɪsᵻs/) lies internal to the thoracic cage, anteriorly. It is a thin plane of muscular and tendinous fibers, situated upon the inner surface of the front wall of the chest. It is in the same layer as the subcostal muscles and the innermost intercostal muscles.

It arises on either side from the lower third of the posterior surface of the body of the sternum, from the posterior surface of the xiphoid process, and from the sternal ends of the costal cartilages of the lower three or four true ribs.

Its fibers diverge upward and lateralward, to be inserted by slips into the lower borders and inner surfaces of the costal cartilages of the second, third, fourth, fifth, and sixth ribs.

The lowest fibers of this muscle are horizontal in their direction, and are continuous with those of the transversus abdominis; the intermediate fibers are oblique, while the highest are almost vertical.

This muscle varies in its attachments, not only in different subjects, but on opposite sides of the same subject.

The muscle is supplied by the anterior rami of the thoracic spinal nerves (intercostal nerves).