Digestion is the physiological process by which large molecules of food are broken down into smaller molecules to be absorbed and utilized by the body.Digestive system is formed of: Alimentary tract (GUT) or gastrointestinal tract (GIT), digestive glands. GIT MOTILITY includes: Peristaltic movement (peristalsis), Mixing (segmenting) movements andIndividual movements of GIT like Mastication (chewing),Swallowing (Deglutition). Secretory and digestive functions of GIT: Presence of food in GIT segments ¿ secretion of moderate to large quantities of digestive juices via: 1-Tactile or chemical stimulation of the mucosa 2-Mechanical distension