Calories in food provide your body with the energy it needs to complete vital processes such as cellular maintenance and reproduction, respiration, digestion and expulsion of waste. If you cannot digest food, you cannot provide your body with the energy it needs for these processes, which can result in health complications and death. Throughout the digestive process, your body breaks down the food you eat into smaller, component nutrients that are then absorbed and used throughout your body .
The Mouth: Mechanical Digestion
The moment you take a bite of food, digestion begins. Your teeth begin to mechanically digest your food, breaking your bite into tiny pieces that can be swallowed easily. Saliva lubricates your food for easier swallowing. It also contains an enzyme that begins to break down carbohydrates, which are composed of chemical compounds that take longer to break down than other nutrients. Without saliva, it would be difficult for carbohydrates, which provide the most energy to your body, to break down and provide your body with energy it needs to perform daily activities.
The Stomach: Chemical Digestion
Food moves through your esophagus, or throat, and into your stomach, where it is introduced to HCl, or hydrochloric acid, as well as digestive enzymes produced by your liver, gallbladder and pancreas. Your stomach is a very acidic environment that further breaks down chemical compounds in your food. The acidic activity in your stomach creates chyme, a liquid substance that contains the broken-down byproducts of your food. Chyme is released into the small intestine. The acidic environment in your stomach is necessary to break down the nutrients your food contains.
The Intestines: Absorption
Your small intestine is covered with millions of villi, or microscopic cells that absorb the nutrients in chyme. From the small intestine, nutrients are sent all over your body to give your body the energy it needs to perform tasks such as cellular maintenance, regeneration or immune resistance. Food that is not absorbed in the small intestine moves on to the large intestine, where liquid is removed from chyme and is incorportated into solid waste for excretion. The intestines are where the nutrients you've consumed are absorbed for transport and eventual use.
Expulsion
Without expelling the waste that builds up in your body, you would become extremely ill. Water is removed from chyme in the colon, which absorbs salt as well. Bacteria that populate the colon digest remaining food products. The rectum stores waste until it is expelled through the anus. Although it might not seem like an important part of digestion, expulsion finishes the cycle and keeps your body from building up waste products from your food that your body cannot use.
