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