Describe the structure and function of the human respiratory system, including the role of alveoli in gas exchange.
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Describe the structure and function of the human respiratory system, including the role of alveoli in gas exchange.
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1. Nasal and Oral Cavities: Air enters the respiratory system through either the nose or mouth. The nasal passages help filter, humidify, and warm the incoming air.
2. Pharynx and Larynx: The air then travels through the pharynx (throat) and larynx (voice box) before reaching the trachea.
3. Trachea: The trachea is a flexible tube that carries air from the larynx to the bronchial tubes. It's lined with cilia and mucus-producing cells to trap foreign particles and move them away from the lungs.
4. Bronchial Tubes: The trachea divides into two bronchial tubes, one leading to each lung. These tubes further divide into smaller bronchioles, which eventually reach the alveoli.
5. Alveoli: Alveoli are tiny, air-filled sacs located at the end of bronchioles within the lungs. They are the primary sites for gas exchange in the respiratory system. Oxygen from inhaled air diffuses across the thin alveolar walls into the bloodstream, while carbon dioxide, a waste product, moves in the opposite direction, from the blood into the alveoli.
6. Lungs: The lungs contain numerous bronchial tubes and alveoli. The right lung has three lobes, while the left lung has two, allowing for efficient gas exchange.
7. Diaphragm and Intercostal Muscles: Breathing is controlled by the diaphragm and intercostal muscles. Contraction of the diaphragm increases the volume of the chest cavity, lowering air pressure and causing inhalation. Relaxation of these muscles leads to exhalation.
The function of the respiratory system is to provide the body with a continuous supply of oxygen for cellular respiration while removing carbon dioxide, a metabolic waste product. This process, known as gas exchange, occurs in the alveoli.
During inhalation, oxygen-rich air is drawn into the lungs and diffuses across the alveolar walls into the pulmonary capillaries, binding to hemoglobin in red blood cells for transport to body tissues. At the same time, carbon dioxide, which has been transported by the blood, is released into the alveoli for exhalation.
Overall, the respiratory system ensures the body receives oxygen for energy production and expels carbon dioxide to maintain proper pH levels and eliminate waste gases.