When we eat, the nutrients and energy we need to function must be extracted from the food and absorbed into the body. The process responsible for this is known as digestion. The human digestive system must be able to process our omnivorous eating habits and diet, and have adapted it to function at an optimal level and is controlled by our autonomic nervous system through the brain. The digestive system is a collective of automated processes and organs. , enzymes, secretions, certain accessory organs, and a duct (or tube) that begins at the mouth and ends at the anus, called alimentary. The processes that take place along the digestive tract determine how we absorb these various nutrients, differentiating what the body can use for survival and function, and what it does not need or is surplus to. to his needs. This excess food passes through the digestive tract to the opposite end and is excreted as waste. The entire digestive process begins with the mouth. When we eat and absorb food, the chewing action in the mouth uses the jaw, muscles and teeth to grind, crush and break solid food masses into smaller particles. Food is moistened by saliva, a secretion released from the small ducts in the mouth. An enzyme in saliva, called Amylase, works to dissolve certain food particles and break down starchy foods, turning them into glucose. The benefit of this reduction in food size, throughout the digestive tract, is to maximize surface area and allow our bodies to absorb nutrients more easily and quickly. Mucus also found in saliva keeps the mouth and upper digestive tract lubricated. When we swallow food, it passes through the mouth and begins its journey to the pharynx and down the esophagus to the middle of the paper.... .. of proteins, carbohydrates and fats. The villi also contain lymph nodes to help fight antigens ingested with food. When chyme leaves the small intestine, it enters the large intestine at the cecum. The large intestine is wider but considerably shorter than the small intestine. It is in the large intestine that excess bile salts and water are removed to give food waste a denser consistency. Finally, food waste passes through another sphincter and into the intestine where it must pass through a final sphincter before leaving the body at the anus. The entire digestion process usually takes about three days but can be affected by bacteria, illness or disease. and is fully automated. The brain controls the autonomic system to influence the involuntary contraction and relaxation of the muscles that make up the walls of the digestive tract..