Digestive Function Digestive system: the organ system that processes food and then voids it Ingestion: intake of food Digestion: mechanical, chemical breakdown of food so it is useable by body Absorption: uptake of nutrients to be delivered by the blood and lymph Defecation: voiding of undigested residue

Digestion location Mesenteries: loose connective tissue that suspend the intestine and stomach, this causes freedom of movement while processing food Most of digestion process occurs under the diaphragm in the stomach and intestine

Mouth Oral cavity: most of the mechanical processing occurs here Process of chewing mixes food with saliva that contains enzymes that break down simple starches to be absorbed by vessels in cheek wall (Bolus) Know the lingual Papillae Function and types of teeth, fig 25.6

Swallowing The pharynx starts the process as food passes the upper esophageal sphincter closes, allowing food to enter esophagus without air As food passes through the esophagus smooth muscle that surrounds the esophagus contract in a wave like motion called peristalsis to push food down

Stomach The main function is to mix bolus with stomach acid (Chyme) Chemical and mechanical digestion occur in the stomach J-shaped organ with the lesser and greater curvature Broken down into 4 regions cardiac, fundus, corpus, and pyloric

Stomach The walls made of several types of cells Mucous cells: produce thick mucus layer that protects tissue from stomach acid Stem cells: cells that are in constant production to replace cells that die Parietal cell: produce acid, intrinsic factor Chief cells: produce pepsinogen Enteroendocrine cells: produce hormones that regulate digestion

Secretions Stomach acid: high concentration HCl with a Ph of 0.8 Pepsinogen: activated by HCl and changes into pepsin to digest protein Intrinsic factor: key for Vit B12 uptake

Vomiting Vomiting: forceful ejection of chyme Controlled by the emetic center found in the medulla oblongata Nausea: sense of stomach discomfort Retching: precedes vomiting, thoracic expansion and abdominal contraction dilates esophagus and relaxes lower esophageal sphincter, chyme travels up but settles in stomach

Vomiting Vomiting occurs when abdominal contraction and thoracic pressure force the upper esophageal sphincter open Projectile vomiting: is the sudden onset of vomiting without nausea and retching