Muscle
Transversus thoracis
Deep muscle slips behind the sternum
High-yield
Remember its relation to the internal thoracic artery: the artery runs between this deep muscle and the more anterior chest-wall structures.
Overview
From the back of the lower sternum, thin slips spread toward the inner costal cartilages. The muscle lies in the deepest chest-wall layer, with the internal thoracic vessels on its anterior side.
Reference facts
- Origin
- Posterior lower sternum and xiphoid region
- Insertion
- Inner surfaces of costal cartilages, typically ribs 2–6
- Innervation
- Intercostal nerve branches, commonly T2–T6
- Action
- Weakly draws the costal cartilages downward during active expiration
- Blood supply
- Branches of the internal thoracic artery
Clinical correlation
The nearby internal thoracic artery is often used in coronary bypass surgery. The muscle also forms a boundary of a regional-anesthesia plane, so this vessel relationship matters during specialist procedures.
Frequently asked questions
What does the transversus thoracis do?
The transversus thoracis weakly draws the costal cartilages downward during active expiration.
What nerve innervates the transversus thoracis?
The transversus thoracis is innervated by the intercostal nerve branches, commonly T2–T6.
Where does the transversus thoracis attach?
Origin: Posterior lower sternum and xiphoid region. Insertion: Inner surfaces of costal cartilages, typically ribs 2–6.
What is the blood supply of the transversus thoracis?
Branches of the internal thoracic artery.