Diaphragm openings | ANATOMY
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The diaphragm is a double-domed musculotendinous sheet, located at the inferior-most aspect of the rib cage. It serves two main functions:
Separates the thoracic cavity from the abdominal cavity (the word diaphragm is derived from the Greek ‘diáphragma’, meaning partition).
Undergoes contraction and relaxation, altering the volume of the thoracic cavity and the lungs, producing inspiration and expiration.
In this article, we shall look at the anatomy of the diaphragm – its attachments, actions and associated neurovascular structures.
The diaphragm is located at the inferior-most aspect of the ribcage, filling the inferior thoracic aperture. It acts as the floor of the thoracic cavity and the roof of the abdominal cavity. The attachments of diaphragm can be divided into peripheral and central attachments. It has three peripheral attachments:
1.Lumbar vertebrae and arcuate ligaments.
2.Costal cartilages of ribs 7-10 (attach directly to ribs 11-12).
3.Xiphoid process of the sternum.
The parts of the diaphragm that arise from the vertebrae are tendinous in structure, and are known as the right and left crura:
Right crus – Arises from L1-L3 and their intervertebral discs. Some fibres from the right crus surround the oesophageal opening, acting as a physiological sphincter to prevent reflux of gastric contents into the oesophagus.
Left crus – Arises from L1-L2 and their intervertebral discs.
The muscle fibres of the diaphragm combine to form a central tendon. This tendon ascends to fuse with the inferior surface of the fibrous pericardium. Either side of the pericardium, the diaphragm ascends to form left and right domes. At rest, the right dome lies slightly higher than the left – this is thought to be due to the presence of the liver.
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