diáfragma

Diáfragma is a term used in anatomy and optics to refer to a partition or thin muscle that divides a body cavity from another region. The word derives from Greek dia- “through” and phragma “fence” or “partition.” In human anatomy, the diaphragma describes the musculotendinous sheet that separates the thoracic cavity from the abdominal cavity and plays a central role in breathing.

Anatomy and structure: The diaphragma consists of a central tendon, around which muscle fibers insert from three regions: a sternal part attaching to the posterior surface of the xiphoid process, a costal part originating from the inner surfaces of the lower six ribs and their cartilages, and a lumbar part formed by two crura attaching to the upper lumbar vertebrae. The major openings are the caval opening for the inferior vena cava at about T8; the esophageal hiatus for the esophagus and vagal trunks at around T10; and the aortic hiatus for the aorta at about T12. The diaphragm is innervated mainly by the phrenic nerves (C3–C5) and receives blood from the inferior phrenic arteries and branches of the internal thoracic arteries.

Function: Contraction of the diaphragma flattens it and increases the vertical dimension of the thoracic cavity, drawing air into the lungs during inspiration. Relaxation allows elastic recoil during expiration. The muscle also contributes to changes in intra-abdominal and intrathoracic pressures that aid venous return and activities such as coughing or vomiting.

Clinical significance: Problems include diaphragmatic hernias (most commonly Bochdalek and Morgagni), diaphragmatic paralysis from phrenic nerve injury, and diaphragmatic eventration. A hiatal hernia is a related condition where abdominal contents herniate through the esophageal hiatus.

Other uses: In optics and photography, the diaphragm (aperture) is the adjustable opening in a lens that controls light transmission and depth of field. The term is used in several languages as diafragma or diaphragma.