- diaphragm
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/duy"euh fram'/, n.1. Anat.a. a muscular, membranous or ligamentous wall separating two cavities or limiting a cavity.b. the partition separating the thoracic cavity from the abdominal cavity in mammals.2. Physical Chem.a. a porous plate separating two liquids, as in a galvanic cell.b. a semipermeable membrane.3. a thin disk that vibrates when receiving or producing sound waves, as in a telephone, microphone, speaker, or the like.4. Also called pessary. a thin, dome-shaped device, usually of rubber, for wearing over the uterine cervix during sexual intercourse to prevent conception.5. a plate with a hole in the center or a ring that is placed on the axis of an optical instrument, as a camera, and that controls the amount of light entering the instrument.6. a plate or web for stiffening metal-framed constructions.v.t.7. to furnish with a diaphragm.8. to reduce the aperture of (a lens, camera, etc.) by means of a diaphragm.[1350-1400; ME diafragma < LL diaphragma < Gk diáphragma the diaphragm, midriff, equiv. to dia- DIA- + phrágma a fence]
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The principal muscle used in respiration, it is also important in coughing, vomiting, excretion, and other expulsive functions. Spasms of the diaphragm produce hiccups. The aorta passes behind the diaphragm; the inferior vena cava and esophagus pass through it. Protrusion of part of the stomach above the diaphragm is called a hiatal hernia.* * *
▪ anatomydome-shaped, muscular and membranous structure that separates the thoracic (chest) and abdominal cavities in mammals; it is the principal muscle of respiration.The muscles of the diaphragm arise from the lower part of the sternum (breastbone), the lower six ribs, and the lumbar (loin) vertebrae of the spine and are attached to a central membranous tendon. Contraction of the diaphragm increases the internal height of the thoracic cavity, thus lowering its internal pressure and causing inspiration of air. Relaxation of the diaphragm and the natural elasticity of lung tissue and the thoracic cage produce expiration. The diaphragm is also important in expulsive actions—e.g., coughing, sneezing, vomiting, crying, and expelling feces, urine, and, in parturition, the fetus. The diaphragm is pierced by many structures, notably the esophagus, aorta, and inferior vena cava, and is occasionally subject to herniation (rupture). Small holes in the membranous portion of the diaphragm sometimes allow abnormal accumulations of fluid or air to move from the abdominal cavity (where pressure is positive during inspiration) into the pleural spaces of the chest (where pressure is negative during inspiration). Spasmodic inspiratory movement of the diaphragm produces the characteristic sound known as hiccupping (hiccup).* * *
Universalium. 2010.
