Digestion is a complex process involving specialized anatomical and physiological adaptations for the absorption of nutrients. Its purpose is to prepare food for use by cells and organs throughout the body. Because large food particles cannot reach cells, the process of digestion breaks the food down into nutrients that can be absorbed into the blood stream and carried to any cell in the body. The methods of digestion are mechanical and chemical. Each segment of the digestive system has a special design to perform a unique function that is an essential part of the digestive process.
Digestion begins in the mouth and is completed at the anus. As food moves through the digestive tract, it passes through several compartments. Accessory organs that produce digestive enzymes drain their contents into the compartments at different points along the way. Each compartment and accessory organ serves a specific function. At each stage, the food is transformed into a slightly different form that allows it to be passed along to the next compartment. As it moves through the digestive tract, nutrients and water are extracted, producing waste. The waste products are eventually eliminated.
The coordination of functions is complicated. Signaling between the nervous and endocrine systems occurs at both the local cellular level as well as throughout the entire body. Through the process of digestion, food is transformed from large complex particles into basic elements that are then easily absorbed into the blood stream.