Massage & Bodywork

January/February 2010

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functional anatomy BY CHRISTY CAEL DIAPHRAGM The diaphragm is a dome-shaped muscle that forms a seal around the bottom of the rib cage. This seal separates the thoracic and abdominal cavities with several openings for blood and lymph vessels, nerves, and structures of the digestive system. The muscle fibers of the diaphragm form a ring around the bottom of the rib cage and converge in the center to form the central tendon. It is helpful to visualize the diaphragm like an umbrella opened at the bottom of the rib cage. The muscle fibers correspond with the domed fabric and the central tendon is similar to the handle. The diaphragm is the primary DIAPHRAGM Attachments • Origin: ribs 7–12, inner surfaces and costal cartilages, xiphoid process of sternum, and bodies of L1–2 • Insertion: central tendon Actions • Expands thoracic cavity during inhalation Innervation • C3-5 • Phrenic nerve muscle of breathing. As it contracts, the central tendon is pulled down toward the abdominal cavity. The dome then flattens, increasing the space inside the thoracic cavity and decreasing its internal air pressure. Decreased air pressure within the cavity prompts air to flow inward from outside the body (inhalation) to equalize air pressure. This mechanism is how the lungs fill with air. As the diaphragm relaxes, the muscle relaxes upward and returns to its domed shape, decreasing the space within the thoracic cavity. Increased pressure within the thoracic cavity prompts air to flow out of the lungs (exhalation), again equalizing air pressure. connect with your colleagues on 83

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