Expansion
Transversus thoracis in front, innermost intercostals laterally, subcostals behind
Expansion
The innermost layer of the thoracic wall is incomplete and is named by region:
- Anteriorly - transversus thoracis, radiating from the back of the sternum to costal cartilages 2 to 6
- Laterally - innermost intercostal muscles
- Posteriorly - subcostal muscles, crossing more than one space
Deep to all of them lies the endothoracic fascia, and deep to that the parietal pleura. This is the plane a surgeon develops to strip pleura from the chest wall, and the layer that must be crossed by any needle entering the pleural cavity.
The neurovascular bundle lies between the internal and innermost layers, which is the anatomical basis of the intercostal nerve block.