Cellular respiration (CR) is the process by which cells convert glucose and oxygen into energy (ATP), carbon dioxide, and water. The circulatory, respiratory, and digestive systems work together to support this process.
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Digestive System: This system breaks down food (glucose) into smaller molecules (like glucose) that can be absorbed into the bloodstream. Nutrients from digested food enter the blood via the intestines.
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Respiratory System: This system brings in oxygen from the atmosphere through inhalation. In the lungs, oxygen diffuses into the blood while carbon dioxide (a waste product of CR) is expelled from the blood into the lungs.
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Circulatory System: The heart pumps oxygen-rich blood (containing oxygen from the respiratory system and glucose from the digestive system) to cells throughout the body. After CR occurs in the cells, carbon dioxide and water (the outputs of CR) are produced. The circulatory system then transports carbon dioxide back to the lungs for exhalation and carries water away to be used or excreted.
In summary, the digestive system provides glucose, the respiratory system supplies oxygen, and the circulatory system distributes these inputs to cells. The circulatory system also removes the outputs (carbon dioxide and water) produced by cellular respiration.