One of the most well-defined systems in the body is the digestive system. It is made up of the digestive tract, and the glands that are linked with it. The liver and pancreas, for example, are connected to the main tract by ducts, or tubes, and dump their products into the system, such as enzymes. The functions of the digestive system include the following:

Ingestion – happens when food enters the digestive tract through the mouth
Mechanical Processing – involves shearing and crushing; makes food easier to propel along the digestive tract
Digestion – refers to the chemical breakdown of food for absorption by the digestive epithelium
Secretion – involves the release of acids, water, enzymes, and other substances by the epithelium of the digestive tract or by glandular organs
Absorption – the movement of organic substrates, electrolytes, vitamins, and water across the digestive epithelium tissue
Excretion – refers to the removal of waste products through defecation