Digestive System

• Digestion occurs in the alimentary canal which is a long tube of organs which runs through the mouth to the anus.
• Mechanical digestion is the breakdown of food into tiny particles and mixes them with digestive juices (ex. chewing)
• Chemical digestion is the breakdown of non-absorbable food molecules using chemical reactions catalyzed by enzymes
• The accessory organs are necessary for the digestive process but are not a direct part of the digestive tract. They release substances into the digestive tract through ducts
• The walls of the digestive tract consists of mucous membrane, submucosa, muscular externa and serosa

  
• The digestive tract consists of the mouth, pharynx, esophagus, stomach, small intestine and large intestine
• Chewed food mixed with saliva is called bolus
• The oral cavity contains teeth which are incisors, lateral, canine, premolars, and molars for adults
• Salivary amylase is an watery enzyme mixture containing mucus which facilitates digestion of starchy foods
• Between the distal or end of the stomach and the small intestine is the pyloric sphincter
• Between the esophagus and stomach is the lower esophageal sphincter (LES)
• Hydrochloric acid is a strong acid that softens the connective tissue in meat and destroys foreign organisms
• Parietal cells secrete and release hydrochloric acid
• Pepsin is a protein-digesting enzyme produced by the mixture of HCl and pepsinogen
• Pepsinogen is produced by the chief cells
• The semi-liquid mixture of gastric juice and food that leaves the stomach to enter the small intestine is called chyme
• Enteroendocrine cells release a variety of chemical messengers such as histamine, serotonin, and somatostanin
• G cells produce gastrin
• The 3 phases of gastric secretion are cephalic, gastric and intestinal phases
• Cephalic phase is triggered by aroma, taste, sight, or thought of food which triggers our brain
• Gastric phase is when the local neural and hormonal mechanisms are initiated once the food reaches the stomach
• Intestinal phase is when gastric secretion begins with a brief stimulatory component followed by inhibition