Diaphragm (definition of)

In anatomy, the word diaphragm usually refers to the muscular tissue separating the chest and thorax from the abdomen (thoracic diaphragm), but can also refer to the urogential diaphragm that separates the perineal sac from the upper pelvis as well as the pelvic diaphragm, which consists of two muscles called the levator ani and the coccigeus, which support the bladder, intestines and (in women) the uterus.

The thoracic diaphragm extends across the bottom of the rib cage. It is dome-shaped; when it contracts, it allows the lungs to expand and take in air; when it relaxes, the lungs contract and expel air. In addition, the diaphragm assists in expelling vomit as well as waste products (feces and urine) by increasing intra-abdominal pressure.

Although cancer can affect virtually any tissue in the body, when it comes to mesothelioma (like peritoneal mesothelioma) the diaphragm is likely to be affected, even though the disease usually does not attack the diaphragm first; more often, cancer spreads to this tissue from the pleural or peritoneal lining.