What is the superior thoracic aperture?

The superior thoracic aperture, also called the thoracic inlet, is the narrow upper opening of the thoracic cavity that connects to the root of the neck. Clinicians often refer to it as the "thoracic outlet" because vital structures like arteries and nerves emerge here, but anatomists prefer "inlet" as it's where air and food enter the thorax.

What are the boundaries of the thoracic inlet?

The boundaries are: anteriorly by the superior border of the manubrium sterni, posteriorly by the anterior surface of the T1 vertebra, and laterally by the medial border of the first rib and its costal cartilage on each side. The inlet is tilted at about 45° downward and forward due to the sloping first rib.

What structures pass through the superior thoracic aperture?

Many vital structures pass through, including arteries like the internal thoracic and left subclavian, nerves like the vagus and phrenic, veins like the brachiocephalic, and others such as the thoracic duct, esophagus, trachea, and lung apices.

What is Sibson's fascia and what does it do?

Sibson's fascia, or the suprapleural membrane, is a dense fascial sheet that forms a protective diaphragm over the thoracic inlet on each side. It protects the cervical pleura and lung apex and maintains neck stability by resisting respiratory pressure changes, attaching from the C7 transverse process to the first rib.

What is thoracic inlet syndrome?

Thoracic inlet syndrome, also called Scalenus Anterior Syndrome or Cervical Rib Syndrome, occurs when the subclavian artery and lower trunk of the brachial plexus are compressed. This can be due to a hypertrophied scalenus anterior muscle or a cervical rib, leading to symptoms like pain, numbness, hand muscle wasting, and weak pulse.

What is the shape and size of the thoracic inlet?

The thoracic inlet is kidney-shaped (reniform) with approximate dimensions of about 4.5 inches transversely and 2.5 inches anteroposteriorly. Its oblique orientation allows the cervical pleura and lung apex to project into it.

Thoracic Inlet – Superior Thoracic Aperture Anatomy