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The breakdown of food and the absorption of nutrients Digestion Breakdown of food and Absorption of nutrients Digestion Mechanical breakdown: Food broken into smaller pieces without changing the chemical composition Chemical breakdown: Food broken down into smaller chemical compounds Mouth Receives food Begins mechanical breakdown Salivary Glands Secrete saliva Saliva moistens, binds, and digests foods Amylase (begins breakdown of carbohydrates) Pharynx Posterior to the mouth Leads to the esophagus Esophagus Passes food from pharynx to stomach Just over 2 feet long Stomach Mixes food with gastric juices Has thick folds called rugae Gastric Juices Pepsin: begins the digestion of proteins Hydrochloric acid: provides acidic environment needed for pepsin to function Secretions that line the stomach to protect it from self-digestion Small Intestine Duodenum, jejunum, and ileum Attached to abdominal wall by the mesentery membrane Intestinal villi: increase surface area Almost all absorption takes place here Large Intestine Not much digestion here Absorbs water Bacteria (intestinal flora) breaks down some particles Rectum Final section of large intestine Temporary storage of feces Anus Opening to the outside environment Two sphincter muscles, one under involuntary control, the other under voluntary control
