Diaphragma

Diaphragma is a Latin term used in anatomy to denote a partition or wall that divides two spaces. The most familiar example is the diaphragm, a dome-shaped musculotendinous partition that separates the thoracic and abdominal cavities and serves as the primary muscle of respiration.

The diaphragm consists of a central tendinous part, the central tendon, surrounded by muscular fibers that arise from three main regions. The sternal part originates from the inner surfaces of the low sternum, the costal part from the internal surfaces of the lower six ribs and their cartilages, and the lumbar part from the upper lumbar vertebrae via the right and left crura and from the arcuate ligaments. The right and left crura attach to the vertebral bodies, with the right typically spanning L1–L3 and the left L1–L2. The diaphragm is pierced by three major openings—the caval opening for the inferior vena cava, the esophageal hiatus for the esophagus, and the aortic hiatus for the aorta—along with accompanying vessels and nerves.

Nerve and blood supply are essential to its function. Motor innervation is provided primarily by the phrenic nerves (C3–C5), with sensory fibers from both phrenic and intercostal nerves. Blood supply comes from the superior and inferior phrenic arteries, as well as branches such as the musculophrenic and lower intercostal arteries.

Functionally, contraction of the diaphragmatic muscle lowers the central tendon and expands the thoracic cavity, increasing vertical volume and aiding inspiration. It also influences intra-abdominal pressure and venous return. Clinically, diaphragmatic integrity is important in conditions such as diaphragmatic paralysis, hernias at the esophageal hiatus, and diaphragmatic eventration.

The term also appears in anatomy as diaphragma sellae, a small dural membrane forming the roof of the pituitary fossa, with a hole for the infundibulum.