Diaphragm

**Diaphragm** separates the thoracic and abdominal cavities, and is dome-shaped at rest. The superior surface of the diaphragm is convex, creating the elevated floor of the thoracic cavity. The inferior surface is concave, creating the curved roof of the abdominal cavity.



Defecating, urination, and even childbirth involve cooperation between the diaphragm and abdominal muscles (Valsalva maneuver). You hold your breath by a steady contraction of the diaphragm; this stabilizes the volume and pressure of the peritoneal cavity. When the abdominal muscles contract, the pressure cannot push the diaphragm up, so it increases pressure on the intestinal tract (defecation), urinary tract (urination), or reproductive tract (childbirth).



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CC licensed content, Shared previously, Axial Muscles of the Abdominal Wall, and Thorax, Authored by: OpenStax College.

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