Table of Contents
Definition and Function of Diaphragm
The thin, flat MUSCLE that forms the floor of the thoracic cavity (chest), establishing a physical barrier between the thoracic cavity and the abdominal cavity. Small openings in the diaphragm allow structures such as the AORTA, inferior VENA CAVA, and ESOPHAGUS to pass through. The lower lobes of the LUNGS and the base of the HEART rest against the diaphragm.
The diaphragm attaches to the lower ribs and spine in the back, then rises along the back of the ribs to dome forward to form the base of the thoracic cavity. Contraction of the diaphragm tightens this dome, pulling it downward to expand the thoracic cavity. The diaphragm has two equal halves, each called a hemidiaphragm, and is the primary muscle of BREATHING.
Health conditions that can involve the diaphragm include HIATAL HERNIA, in which weakness in the musculature around the esophageal opening allows the stomach to bulge upward through the opening. Hiatal hernia typically causes an uncomfortable burning sensation and may result in regurgitating food or GASTROESOPHAGEAL REFLUX DISORDER (GERD). HICCUPS are muscle spasms of the diaphragm.
The Heimlich Maneuver
The Heimlich maneuver, an emergency procedure for ejecting an inhaled object from the TRACHEA, uses the diaphragm to generate a forceful exhalation. Placing a sharp, upward thrust into the diaphragm causes the diaphragm to rapidly contract and relax, sending its dome higher into the thoracic cavity than usual. The effect strongly compresses the LUNGS, forcing them to propel air outward. The force of the air dislodges the object.
For further discussion of the diaphragm within the context of pulmonary structure and function please see the overview section “The Pulmonary System.”
See also BREATHING EXERCISES.