What are the three layers of intrinsic muscles in the thoracic wall?

The intrinsic muscles are arranged in three layers: external intercostal muscle (superficial), internal intercostal muscle (intermediate), and transversus thoracis muscle (deep), which includes intercostalis intimus, subcostalis, and sternocostalis.

How do the external and internal intercostal muscles differ in function?

The external intercostal muscles elevate the ribs during inspiration, while the internal intercostal muscles elevate the ribs during expiration, with perpendicular fiber directions.

Where is the neurovascular bundle located in the thoracic wall?

The neurovascular bundle is located in the neurovascular plane, between the internal intercostal muscle and the intercostalis intimus layer of the transversus thoracis muscle.

What structures line the internal surface of the thoracic wall muscles?

The internal surface is lined by the endothoracic fascia, with the parietal pleura further lining it.

What are the components of the transversus thoracis muscle?

The transversus thoracis muscle includes intercostalis intimus (elevates ribs during expiration), subcostalis (depresses ribs), and sternocostalis (draws down costal cartilages).

What is the action of the levatores costarum muscles?

The levatores costarum muscles elevate and rotate the neck of the ribs and assist in lateral flexion and rotation of the vertebral column.

Intrinsic Thoracic Wall Muscles – Intercostals & More