Also called: thoracic diaphragm
The diaphragm is the dome-shaped muscle separating the chest from the abdomen and is the main muscle of breathing. It arises from the sternum, lower six ribs and lumbar vertebrae and converges on a central tendon. The phrenic nerve (C3-C5) supplies it. Contraction flattens the dome and draws air into the lungs.
| Origin | Sternal part: back of the xiphoid process. Costal part: inner surfaces of the lower six ribs. Lumbar part: lumbar vertebrae by the crura and arcuate ligaments. |
|---|---|
| Insertion | Central tendon of the diaphragm. |
| Innervation | Phrenic nerve (C3-C5) for motor and most sensation. |
| Blood supply | Pericardiacophrenic, musculophrenic and inferior phrenic arteries. |
| Action | Main muscle of inspiration: contraction lowers the central tendon and increases thoracic volume. |
3D model: BodyParts3D (CC BY 4.0), adult male reference anatomy. Highlighted structure shown with nearby bones for context.
Three large openings transmit structures between thorax and abdomen: the vena caval opening at T8, the esophageal hiatus at T10 and the aortic hiatus at T12.
The phrenic nerve, arising from C3, C4 and C5 ("C3, 4, 5 keeps the diaphragm alive").
The inferior vena cava (T8), esophagus and vagus nerves (T10) and the aorta, thoracic duct and azygos vein (T12).
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