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Real-time magnetic resonance imaging of the human thorax during breathing X-ray video of a female American alligator while breathing. Breathing (spiration [1] or ventilation) is the rhythmical process of moving air into and out of the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxygen.
Gas exchange in plants is dominated by the roles of carbon dioxide, oxygen and water vapor. CO 2 is the only carbon source for autotrophic growth by photosynthesis, and when a plant is actively photosynthesising in the light, it will be taking up carbon dioxide, and losing water vapor and oxygen.
In physiology, respiration is the transport of oxygen from the outside environment to the cells within tissues, and the removal of carbon dioxide in the opposite direction to the environment by a respiratory system. [1]
The acini are the basic units of respiration, with gas exchange taking place in all the alveoli present. [6] The alveolar membrane is the gas exchange surface, surrounded by a network of capillaries. Oxygen is diffused across the membrane into the capillaries and carbon dioxide is released from the capillaries into the alveoli to be breathed ...
The oxygen tension (or partial pressure) remains close to 13–14 kPa (about 100 mm Hg), and that of carbon dioxide very close to 5.3 kPa (or 40 mm Hg). This contrasts with composition of the dry outside air at sea level, where the partial pressure of oxygen is 21 kPa (or 160 mm Hg) and that of carbon dioxide 0.04 kPa (or 0.3 mmHg). [6]
The respiratory zone includes the respiratory bronchioles, alveolar ducts, and alveoli, and is the site of oxygen and carbon dioxide exchange with the blood. The respiratory bronchioles and the alveolar ducts are responsible for 10% of the gas exchange. The alveoli are responsible for the other 90%.
Dead space reduces the amount of fresh breathing gas which reaches the alveoli during each breath. This reduces the oxygen available for gas exchange, and the amount of carbon dioxide that can be removed. The buildup of carbon dioxide is usually the more noticeable effect unless the breathing gas is hypoxic as occurs at high altitude.
The primary function of ventilation is the replacement of the stale gases in the lungs with oxygen-rich air through the removal of carbon dioxide for oxygenation of the blood. [5] The oxygen is then supplied to the entire body through the circulatory system.