Thoracic inlet

The superior thoracic aperture, also known as the thoracic inlet or outlet, connects the root of the neck with the thorax.

Gross anatomy

The superior thoracic aperture is kidney-shaped and lies in an oblique transverse plane, tilted anteroinferiorly to posterosuperiorly. It is roughly 10 cm in transverse dimension and 5 cm in AP dimension.

Boundaries

• posteriorly: T1 vertebral body and costovertebral joints
• laterally: first ribs and their costal cartilages
• anteriorly: superior border of the manubrium

Contents

The list of structures that pass through the superior thoracic aperture is long and can be divided into five groups: midline, bilateral, posteriorly, and asymmetric left and right.

• midline from anterior to posterior 
  • sternohyoid and sternothyroid muscles
  • thymic remnants 
  • inferior thyroid veins
  • trachea
  • tracheo-esophageal sulcus containing recurrent laryngeal nerves
  • esophagus
  • thoracic duct displaced to the left
  • longus colli muscles
  • anterior longitudinal ligament 
• laterally on both sides 
  • Sibson's fascia
  • internal thoracic artery
• posteriorly from medial to lateral
  • sympathetic trunk
  • supreme intercostal vein
  • superior intercostal artery
  • ventral ramus of the first thoracic nerve 
• on the left:
  • left common carotid artery
  • left subclavian artery
  • left vagus nerve, between left common carotid and left subclavian arteries
  • left brachiocephalic vein
  • left phrenic nerve 
• on the right
  • brachiocephalic trunk
  • right vagus nerve, lateral to the brachiocephalic trunk
  • right brachiocephalic vein 
  • right phrenic nerve, lateral to the right brachiocephalic vein 

Variants

Variant structures that course through include:

• left vertebral artery from the aortic arch
• left brachiocephalic trunk
• right common carotid artery
• right subclavian artery
• right-sided thoracic duct 

Related pathology

• thoracic outlet syndrome