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The diaphragm is a thin, dome-shaped fibromuscular organ that serves a number of anatomic and physiologic purposes. Its primary physiologic function is that of an air pump, whereby it provides the main mechanical forces of ventilation. When the diaphragm contracts in response to stimulation by the phrenic nerve, it descends into the abdominal cavity, thereby establishing a negative intrathoracic pressure. As a result, air is drawn into the lungs through an open glottis. As the muscle relaxes, it moves upward, forcing air out of the glottis in expiration. Anatomically, the diaphragm serves as a barrier between the thoracic and peritoneal cavities. Defects in the barrier permit herniation of abdominal organs into the chest as a result of the relatively negative intrapleural pressure.

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The diaphragm is an uncommon site of disease, whether benign or malignant. Intimately associated with vital organs on the thoracic and abdominal surfaces, it can be involved with neoplasms from surrounding structures or diffuse pleural or peritoneal cancers. Less commonly, the diaphragm is invaded by metastasis from distant primary tumors. The most common indication for a partial resection of the diaphragm is local invasion by thoracic or abdominal tumors. The location of the diaphragm also makes it susceptible to trauma by either blunt or penetrating mechanisms. Reconstruction or repair of the diaphragm after resection or injury is essential to maintaining its structural and functional integrity. Usually, the diaphragm can be repaired primarily by using simple running or horizontal mattress sutures. Larger defects may require synthetic or semisynthetic grafts. Reconstruction is arguably more important on the left side than on the right, where the liver may prevent herniation of abdominal contents.

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The diaphragm consists of muscle fibers and a noncontractile central tendon (Fig. 127-1). Its muscle fibers originate from the lumbar spine posteriorly via the external and internal arcuate ligaments, the lower six ribs bilaterally, and the xiphisternum anteriorly. The muscle fibers curve upward and form an aponeurotic sheath known as the central tendon of the diaphragm, which serves as the insertion. The muscle fibers and tendons that comprise the diaphragm are arranged in a crossing pattern and are covered by thin layers of pleura and peritoneum. The diaphragm is the major muscle involved in ventilation, and it serves to divide the thoracic and abdominal compartments. The organ has several distinct apertures, through which a number of structures pass, including the vena cava, aorta, and esophagus. The apertures are usually sealed with thin layers of tissue that prevent communication between the thoracic cavity and the peritoneal cavity (Fig. 127-2). Each of the apertures, along with the multiple areas of fusion that occur during normal embryologic development, offers a potential site for visceral herniation.

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Figure 127-1.
Graphic Jump Location

The muscle fibers of the diaphragm originate from the posterior lumbar spine (arcuate ligaments) and curve upward to form an aponeurotic sheath known as the ...

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