Inferior thoracic aperture
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The inferior thoracic aperture is irregular in shape and is more oblique and much larger than the superior thoracic aperture. The diaphragm occupies and closes the inferior thoracic aperture, thereby separating the thoracic and abdominal cavities. For structures to pass between the two cavities, they either pass behind the diaphragm or pass through various diaphragmatic apertures.
- posteriorly: 12th thoracic vertebral body and transverse processes
- posterolaterally: 11th and 12th ribs
- anterolaterally: the costal margins formed by the conjoint costal cartilages of 7th to 10th ribs
- anteriorly: xiphisternal joint
Apart from the diaphragm, the list of structures that pass through the inferior thoracic outlet is best described by considering the various diaphragmatic apertures: