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[Muscular system](https://durgical.com/en/anatomy/system/muscular-system/) · [Chest](https://durgical.com/en/anatomy/region/chest/)

# Transversus thoracis

The transversus thoracis is a thin muscle on the inner surface of the front chest wall, behind the breastbone; it helps pull the [ribs](https://durgical.com/en/anatomy/ribs/) down.

Official name: Transversus thoracis muscle

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## What it is

A thin muscle on the inside of the front chest wall, behind the [sternum](https://durgical.com/en/anatomy/sternum/).

## What it does

Helps pull the ribs down when breathing out.

## Key points

- Part of the innermost muscle layer of the [chest](https://durgical.com/en/anatomy/region/chest/) wall, on the inner surface of the front wall, continuous below with transversus abdominis
- The internal thoracic artery and veins run down on its front surface, which is the plane surgeons dissect when harvesting the artery for coronary bypass
- The anterior branches of the [intercostal nerves](https://durgical.com/en/anatomy/intercostal-nerves/) run between it and the internal intercostals: the target of parasternal (transversus thoracis plane) blocks after sternotomy

## Key facts

**Origin**
Posterior surface of lower sternum (body and xiphoid process)

**Insertion**
Internal surfaces of costal cartilages 2–6

**Action**
Weakly depresses ribs and costal cartilages in expiration

**Nerve**
Intercostal nerves (T2–T6)

**Blood supply**
Internal thoracic artery (anterior intercostal branches)

## Relations

**Superficial**
[Internal thoracic artery](https://durgical.com/en/anatomy/internal-thoracic-artery/) and veins, [parasternal lymph nodes](https://durgical.com/en/anatomy/parasternal-nodes/), [costal cartilages](https://durgical.com/en/anatomy/costal-cartilage/) 2–6 and the [internal intercostals](https://durgical.com/en/anatomy/internal-intercostal-muscles/)

**Deep**
Endothoracic fascia and parietal [pleura](https://durgical.com/en/anatomy/pleura/); near the midline, the [pericardium](https://durgical.com/en/anatomy/pericardium/) in front of the heart

**Below**
Continuous with [transversus abdominis](https://durgical.com/en/anatomy/transversus-abdominis-muscle/) at the costal margin, and close to the sternal part of the [diaphragm](https://durgical.com/en/anatomy/diaphragm/)

## How to find it

Seen from inside the chest, fanning up and out from the back of the lower sternum to the costal cartilages. On parasternal ultrasound it is a thin layer under the internal thoracic vessels and above the pleural line.

## On imaging

Parasternal ultrasound in a longitudinal view, a little lateral to the sternum, shows the costal cartilages, the internal thoracic vessels and, beneath them, this thin muscle over the pleura and the heart.

## Clinical notes

- Internal thoracic artery harvest for coronary bypass lifts the artery off this muscle and the endothoracic fascia
- The parasternal nodes lie on it along the internal thoracic vessels; medial breast cancers can spread to them
- In a parasternal (transversus thoracis plane) block the needle stops just in front of this muscle; the internal thoracic vessels and the pleura right behind are what make ultrasound guidance standard

## Anatomical variants

- Its slips vary a lot from side to side and between people: the number of digitations and the highest cartilage reached differ

## Test yourself

Think of the answer, then tap the question to see it.

## What are the attachments of the transversus thoracis?

From the back of the lower sternum (body and xiphoid process) to the inner surfaces of costal cartilages 2–6.

## Which vessels run on the front surface of the transversus thoracis, and why does this matter in surgery?

The internal thoracic artery and veins; surgeons lift the artery off this muscle when harvesting it for coronary bypass.

## Which nerves are targeted in a transversus thoracis plane block after sternotomy?

The anterior branches of the intercostal nerves, which run between the transversus thoracis and the internal intercostals.

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Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
musculus transversus thoracis TA2 2315

**Official Spanish (DeCS)**
Músculo transverso del tórax

**English (TA2)**
Transversus thoracis muscle

## Related

- [Intercostal nerves](https://durgical.com/en/anatomy/intercostal-nerves/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Thorax, Wall Movements](https://www.ncbi.nlm.nih.gov/books/NBK526023/); [Anatomy, Thoracotomy and the Collateral Intercostal Neurovascular Bundle](https://www.ncbi.nlm.nih.gov/books/NBK544368/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/transversus-thoracis-muscle/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/transversus-thoracis-muscle/