- published: 16 May 2015
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In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm (Ancient Greek: διάφραγμα diáphragma "partition"), is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity (heart, lungs & ribs) from the abdominal cavity and performs an important function in respiration. A diaphragm in anatomy can refer to other flat structures such as the urogenital diaphragm or pelvic diaphragm, but "the diaphragm" generally refers to the thoracic diaphragm. Other vertebrates such as amphibians and reptiles have diaphragms or diaphragm-like structures, but important details of the anatomy vary, such as the position of lungs in the abdominal cavity.
The diaphragm functions in breathing. During inhalation, the diaphragm contracts, thus enlarging the volume of the thoracic cavity (the external intercostal muscles also participate in this enlargement). This reduces intra-thoracic pressure: In other words, enlarging the cavity creates suction that draws air into the lung, or lungs.