The
lower opening of the thorax
The superior thoracic aperture, also known as the thoracic outlet, or thoracic inlet refers to the opening at the top of the thoracic cavity. It is also clinically referred to as the thoracic outlet, in the case of thoracic outlet syndrome. A low ...
is formed by the twelfth thoracic vertebra behind, by the eleventh and twelfth ribs at the sides, and in front by the cartilages of the tenth, ninth, eighth, and seventh ribs, which ascend on either side and form an angle, the infrasternal angle or subcostal angle, into the apex of which the
xiphoid process projects.
Pregnancy causes the angle to increase from 68° to 103°.
References
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Bones of the thorax