The Digestive System

Processes of digestive system activity

-Ingestion -Propulsion: moves food through canal, swallowing, peristalsis (alternating waves of contraction and relaxation of muscles) -Mechanical breakdown: increases SA of food to prepare for digestion, chewing, mixing food with saliva, churning in stomach, segmentation (rhythmic local constrictions of the small intestine to mix food with digestive juices and make absorption more efficient) -Digestion: catabolic steps, enzymes secreted into lumen of canal to break down food -Absorption: digested end products from lumen of GI tract through mucosal cells by active or passive transport into blood or lymph -Defecation: elimination of indigestible substances

Alimentary canal

-gastrointestinal tract -continuous muscular tube that winds through the body from the mouth to the anus -digests food -absorbs fragments -organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine

peritoneum of digestive organs

-most extensive of serous membranes -Visceral peritoneum: covers external surfaces of most digestive organs, continuous with parietal peritoneum -parietal peritoneum: lines body wall -peritoneal cavity: between the two peritoneums, contains slippery fluid secreted by serous membranes which allows mobile digestive organs to glide easily across one another -mesentery: double layer of peritoneum, sheet of two serous membranes fused back to back, provides routes for blood vessels, lymphatics and nerves to reach the digestive viscera, hold organs in place and store fat --dorsal: attaches to posterior abdominal wall --ventral: from liver to anterior abdominal wall -retroperitoneal organs: no mesentery, adhere to dorsal abdominal wall, lie posterior to the peritoneum, pancreas and duodenum and parts of large intestine -Intraperitoneal/peritoneal organs: digestive organs keep their mesentery and remain in the peritoneal cavity -peritonitis: inflammation of peritoneum, piercing abdominal wound or perforating ulcer or poor sterile technique during surgery or burst appendix

Accessory digestive organs

-teeth, tongue, gallbladder, salivary glands, liver, pancreas