Digestive System Chapter 14

Functions Ingestion Propulsion Food breakdown: mechanical Peristalsis Segmentation Food breakdown: mechanical Food breakdown: chemical Absorption Defecation

Oral Cavity Mechanical breakdown of food Enzymatic digestion of starches due to saliva

Alimentary Canal

Stomach Three muscle layers allow for churning motion Rugae allow for expansion Gastric Pits Gastric glands Enteroendocrine cells which secrete hormones Chief cells which secrete pepsinogen Parietal cells which secrete H+ and Cl- Once food leaves stomach it becomes chyme

Stomach

Small Intestine Plicae Circularis increase surface area and funnel chyme through the small intestine Villi are comprised of microvilli amd small number of goblet cells Microvilli contain brush border enzymes in plasma membrane Duodenal papilla allow pancreatic juice and bile to enter small intestine

Small Intestine Three sections Lacteal –lymphatic capillary Duodenum –characterized by Brunner’s gland in submucosa Jejunum –longest section, absence of glands and lymphatic tissue in submucosa Ileum –characterized by presence of Peyer’s patches in submucosa Lacteal –lymphatic capillary

Large Intestine Absorb water Numerous goblet cells Haustra Appendix is found at the junction of Ileum and Cecum

Accessory Glands Salivary glands –salivary amylase Pancreas –buffer as well as small amount of enzymes Liver –filters blood, produces bile (emulsifies fats) Gall Bladder stores bile

Homeostatic Imbalances Peritonitis Gall Stones Pancreatitis Hepatitis Cirrhosis Jaundiced

Process of Digestion Oral Cavity to Anus

Process of Digestion Begins before we eat: thought, sight, smell of food primes salivary glands and stomach Oral Cavity – mechanical breakdown (deglutination) Stomach – mechanical \ chemical breakdown Gastrin –stimulates chief and parietal cells Histamine –stimulates parietal cells

Process of digestion Segmentation and peristalsis Small Intestine –chemical breakdown and absorption Gastrin –stimulates gastric glands Somatostatin –inhibits gastric glands Secretin –stimulates pancreas, gall bladder, inhibits gastric glands Cholecystokinin (CCK) –stimulates pancreas, gall bladder Gastric Inhibitory Peptide (GIP) –inhibits gastric glands, stimulates insulin release

Large Intestine Absorption of vitamins, ions and water Chyme becomes feces when delivered to rectum

Nutrition Lipids Protein Vitamins Minerals

Metabolism Cellular Respiration Glycolysis Krebs Cycle

Metabolism

Metabolism and the Liver Glycogen –stored energy Glycogenesis Glycogenolysis Gluconeogenesis Cholesterol LDL –lipids used by cells HDL –lipids filtered by liver (produced as waste) Ratio of the two is what is important