THE DIAPHRAGM

The diaphragm is the primary muscle used in the process of inspiration, or inhalation. It is a dome-shaped sheet of muscle (and connective tissue) that is inserted into the lower ribs. Lying at the base of the thorax (chest), it separates the abdominal cavity from the thoracic cavity. The diaphragm can clearly be seen separating the two cavities (label 16) in the coronal image below. It is a thin, skeletal muscle that can contract voluntarily. 

During inhalation the diaphragm contracts & flattens, increasing the space for the lungs to fill with air. During exhalation the diaphragm relaxes and its dome shape increases, decreasing the thoracic volume and thereby assisting the lungs to empty.

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These are seen below as:

• aorta (label 4)
• oesophagus (label 3)
• Inferior vena cava (label 10)

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See anterior view of the abdomen below: The oesophagus (label 7) and aorta (label 25) can be seen going through the diaphragm. The vena cava is seen on the right side as a hole in the diaphragm (label 10).

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Additional resources:

1. Watch the The Diaphragm gross-anatomy video in Acland's Anatomy

Navigate to Trunk > MSK structures of the Trunk > 3.2.6 Diaphragm (4:14min)

For access you need to be logged in to the library: go to https://guides.lib.monash.edu/mnhs/anatomy_resources then click on Aclands video atlas then type in "diaphragm" to the search bar (the video is the top result).

Checklist to consider:

1. Note the central tendon of the diaphragm
2. Observe the location of the 3 main holes in the diaphragm - the aortic opening, the eosophageal hiatus and vena caval foramen

You do NOT have to learn about the diaphragmatic attachments, muscles or crura.

The structures traversing the diaphragm include: