11.1: Need for Nutritional Homeostasis

A main function of the digestive system is to supply nutrients at proper and fairly steady levels to body cells and thus maintain nutritional homeostasis. Cells require nutritional homeostasis for four reasons. First, many nutrients must be constantly broken down to supply the energy needed to power the ongoing vital functions of the cells. Second, nutrients supply the raw materials needed to synthesize body substances. Some materials are used to enlarge, replace, or repair parts of the body (e.g., muscle cells, RBCs, epidermis); others are used to replace substances that are degraded (e.g., neurotransmitters, hormones) or lost (e.g., water in perspiration, digestive enzymes). Third, nutrients supply materials that assist chemical reactions (e.g., vitamins, certain minerals). Fourth, nutrients such as minerals and water maintain proper volumes and concentrations of body fluids so that blood flows properly and cells are not damaged by excessive shrinking or swelling.

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