The most important of the respiratory muscles is the dome-shaped diaphragm, which separates the thoracic and abdominal cavities and is innervated by the phrenic nerve. Injury to the phrenic nerve associated with birth trauma or cardiothoracic surgery can result in diaphragmatic paralysis, which may lead to respiratory distress in newborns. The initial treatment is supportive, and spontaneous recovery occurs in most cases.
Before addressing the clinical features, diagnosis, and management of the disorder, reviewing the embryology and physiology of the diaphragm is useful.
The diaphragm develops from four embryologic structures:
- Septum transversum
- Pluripotential membranes
- Dorsal mesentery of the esophagus
- Body wall muscles
The septum transversum is first recognizable at the third week of gestation as a mass of mesoderm located ventral to the cervical somites. During the fourth week, it descends and partially separates the thoracic and peritoneal cavities . The openings that remain between the thorax and abdomen are the pleuroperitoneal ducts.