Quick Facts
Origin: Posterolateral aspects of body and xiphoid process of sternum.
Insertion: Internal surfaces of second to sixth costal cartilages and costal ends of adjacent ribs.
Action: Depresses ribs and their costal cartilages.
Innervation: Adjacent intercostal nerves (anterior rami of thoracic nerves).
Arterial Supply: Anterior intercostal branches of internal thoracic artery.
Origin
The transversus thoracis muscle originates from the posterolateral aspects of the body and xiphoid process of the sternum. There can be variations between individuals regarding the origin sites for the transversus thoracis muscle.
Insertion
The fibers of the subcostal muscles travel laterally and insert onto the internal surfaces of the second to sixth costal cartilages and the costal ends of their adjacent ribs.
Key Features & Anatomical Relations
The transversus thoracis muscle (sternocostalis muscle) is one of the muscles of the thorax. It is a broad, flat, skeletal muscle that is found in the anterior thoracic wall. It is located:
- superficial to the endothoracic fascia and parietal pleura;
- deep to the second to six costal cartilages ribs, the internal intercostal muscles, the anterior rami of upper thoracic nerves (intercostal nerves), and the upper anterior intercostal vessels.
Actions
The transversus thoracis muscle depresses the ribs and their costal cartilages (Netter, 2011).
References
Netter, F. H. (2011) Atlas of Human Anatomy. Netter Basic Science Series: Saunders/Elsevier.
