The Nikon MicroscopyU confocal microscopy image gallery was created with a PCM-2000 confocal scanning system interfaced to a Nikon Eclipse E600 upright microscope. Images were recorded in successive z-axis serial sections with C-Imaging Systems software with excitation illumination provided by an argon-ion and/or a helium-neon laser.

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Respiration in humans can be cellular or internal respiration where glucose is oxidized to produce cellular energy; or external respiration, which involves simply taking oxygen-rich air into the lungs and expelling waste carbon dioxide. It is with breathing that the human diaphragm plays a major role. The diaphragm, a layer of muscle and fibrous septum, is connected to the spine at the lumbar vertebrae by two crura or pillars.

Each human lung is in the rib cage bounded below by the diaphragm. Breathing works by making the rib cage larger, decreasing the pressure in the lungs, and air is sucked in (inspiration). Expelling depleted air is the reverse, where the cage collapses and the lung pressure is increased. The breathing action is driven by the contraction and relaxation of the diaphragm. When the diaphragm muscle contracts, it moves downward, making the chest or thoracic cavity longer, while its associated intercostal muscles contract, widening the chest, allowing inspiration. The diaphragm and external intercostal muscles then relax and expiration occurs. The diaphragm is now back in its resting stage due to elastic recoil and the pull of the abdominal muscles.

Breathing via diaphragmatic action accounts for almost all lung exchanges during quiet respiration (e.g., breathing while resting on back) and the thoracic volume increases by 500 to 700 milliliters. During these rest periods, the chest wall appears almost still. Diaphragmatic breathing is more common in children and pregnant women than in adult men. Active breathing, which results in significant changes in the thoracic volume, results in larger and more frequent gas exchanges, but also demands additional energy. Being "winded" or "out-of-breath" occurs when the diaphragm and associated muscles are fatigued due to a buildup of lactic acid, and the person feels breathless.

As part of the autonomic nervous system, the diaphragm and the rest of the breathing apparatus is controlled by the sympathetic and parasympathetic nerves that send signals via acetylcholine releases to the medulla oblongata or spinal bulb, the most primitive part of the vertebrate brain. Fight or flight input results in quick actions to the diaphragm. The diaphragm is also called into action to provide extra power in expulsive behaviors including laughing, crying, coughing, sneezing, vomiting, defecating and urinating, and giving birth. As any singing or acting coach will advise, the power to project the human voice is driven by the diaphragm.