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The lungs are organs that are part of the respiratory system. They allow your body to take in oxygen from the air. They also help remove carbon dioxide from the body.The entire respiratory system works together to breathe air in and out of the lungs. This includes the nose, mouth, larynx, trachea and the bronchial tubes within the lungs.
肺是呼吸系统器官的一部分。肺使机体能从空气中吸收氧气，并将二氧化碳排出体外。整个呼吸系统一起工作使气体进出肺。呼吸系统包括鼻、口腔、咽、气管和肺内的支气管。
Air enters the lungs when we breathe in because the lungs expand. The lungs expand when nearby muscles contract to make the chest cavity larger. These muscles include the dome-shaped muscle called the diaphragm, and the muscles of the rib cage. As the muscles contract and the lungs expand, air is sucked through the nose and mouth.
当吸气时，气体进入肺，因为邻近的肌肉收缩时胸腔扩大使肺扩张。这些肌肉包括穹顶状的膈肌，还有胸腔肌肉。当肌肉收缩，肺扩张，气体被吸进鼻和口腔。
This is known as inhalation. Your nose filters, wets, and warms the air before it passes through the larynx, trachea and the bronchial tubes within the lungs. At the same time, the heart pumps blood rich in carbon dioxide and low in oxygen, to the lungs through the pulmonary arteries. The pulmonary arteries end in a mesh of tiny blood vessels called capillaries. This mesh surrounds the round air sacs called alveoli. The alveoli are like bunches of grapes at the end of the bronchial tubes. When you inhale, air flows down the bronchial tubes and into the alveoli. This inhaled air is oxygen-rich.
这就是吸气。在气体通过咽、气管和肺内的支气管之前，鼻腔会过滤、加温和加湿空气。与此同时，心脏将富含二氧化碳的低氧血通过肺动脉泵入肺。肺动脉最终形成小血管网—毛细血管。毛细血管围绕在充满空气的圆腔——肺泡周围。肺泡位于支气管的末端，就像葡萄串一样。当吸气的时候，空气流入支气管进入肺泡。吸入的空气是富含氧的。
