Anatomy & Function of Digestive System

According to the National Digestive Diseases Information Clearinghouse (NDDIC), the digestive system is composed of the digestive tract---a series of hollow organs joined in a long, twisting tube from the mouth to the anus---and other organs that help the body break down and absorb food. The digestive system works with the other systems in the body to create homeostasis, or a state of equilibrium. Through the digestive system the body obtains essential nutrients, some of which can only be found in foods.

Importance

• The major importance of the digestive system is the process of digestion. During digestion, foods are broken down into a form the body can use for nourishment. The nutrients from food are absorbed as simple molecules in the blood stream. Through the bloodstream, nutrients can travel to any of the cells in the body, where they can be used for growth, repair and energy.

Phases of Digestion

• According to Encarta, digestion happens in two phases: a mechanical phase and a chemical phase. During the mechanical phase, large particles of food are physically broken down into smaller pieces by the teeth. In the chemical phase, digestive chemicals secreted by organs break down individual molecules of food into even smaller particles, so that nutrient molecules can be absorbed and distributed throughout the body.

Organs and Their Functions

• The organs of the digestive system can be divided into two groups: the gastrointestinal tract and accessory organs. The organs of the gastrointestinal tract include the mouth, pharynx, esophagus, stomach, small intestine and large intestine. The accessory organs include the teeth, tongue, salivary glands, gallbladder, liver and pancreas.
  Food is consumed through the mouth. The pharynx works to push the food into the esophagus, where muscles contract to move food along the tract and into the stomach. While in the stomach, food is mixed with gastric juices to produce a substance called chyme. The chyme mixture then moves into the small intestine where virtually all the nutrient absorption into the blood stream occurs. The insoluble product left behind moves into the large intestine, where waste is held until defecation.

Absorption and Transport of Nutrients

• Most nutrients from digested food are absorbed in the small intestine. According to NDDIC, the mucosa of the small intestine contains many folds that are covered with tiny fingerlike projections called villi. The villi are covered with microscopic projections called microvilli, which create a vast surface area through which nutrients can be absorbed. Some nutrients absorbed in the small intestine include carbohydrates, proteins, fats and vitamins.

Controlling the Digestive Process

• The body's central nervous system and various glands control activities that regulate the digestive process, such as the secretion of enzymes and fluids. The main hormones that control digestion are gastrin, secretin and cholecystokinin.