The respiratory system works with the digestive and circulatory systems to make cellular respiration possible. During cellular respiration, your cells use oxygen and glucose to release energy. Carbon dioxide is a waste product of the process. Carbon dioxide must be removed from cells.
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Your body has different kinds of cells. Though they might look different under a microscope, most cells have chemical and structural features in common. In humans there are about 200 different types of cells and within this cells there are about 20 different types of structures or organelles.
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Muscles can also receive messages from the brain when the body temperature decreases. They respond by shivering. Shivering causes the muscles to contract and relax quickly. This process generates heat.
