Transcript Digestion
Digestive System Digestive System • Basic Divisions – Digestive tract – Accessory organs: various exocrine glands • Digestive Processes – Ingestion – Mechanical Processing – Motility •Peristalsis • Digestive Processes – Ingestion – Mechanical Processing – Motility •Peristalsis • Digestive Processes – Ingestion – Mechanical Processing – Motility •Peristalsis •Segmentation movements • Digestive Processes, continued – Chemical digestion – Secretion – Absorption – Excretion and defecation • Non-Digestive Functions of Digestive Tract – Immunity – Storage of iron • Layers of the digestive tract – Mucosa • Epithelium • Lamina propria (areolar CT) • Muscularis mucosae • Layers of the digestive tract, continued – Submucosa • includes the • submucosal plexus • Layers of the digestive tract, continued – Muscularis externa: responsible for peristalsis and segmentation movements • longitudinal layer • circular layer • myenteric plexus • Layers of the digestive tract, continued – Serosa (the visceral peritoneum is an example) • Simple squamous epithelium • Areolar CT Within peritoneal cavity only • Layers of the digestive tract, continued – Adventitia • Dense irregular CT Oral cavity, pharynx, esophagus, rectum • The Peritoneum – Parietal p. – Visceral p. • The mesenteries – Mesentery proper – Mesocolon – Greater omentum – Lesser omentum – Falciform ligament • Accessory structures of the oral (buccal) cavity – Teeth: will cover in lab – Tongue: read textbook – Salivary glands • buccal glands • lingual glands • Oral (buccal) cavity – Salivary Glands • buccal glands • lingual glands • major salivary glands – parotid • Oral (buccal) cavity – Salivary Glands • buccal glands • lingual glands • major salivary glands – parotid – sublingual – submandibular – Structure of salivary glands • glandular epithelium • merocrine cells – Structure of salivary glands • glandular epithelium • merocrine cells • compound tubulo-acinar – Functions of saliva • lubrication for swallowing, speaking • re-mineralizes tooth enamel • buffer • antibodies (IgA) • dissolves food molecules • some chemical digestion • Pharynx – To be discussed with the respiratory system • Esophagus – Structural features • muscular tube about 25 cm long • posterior to larynx, trachea • pierces diaphragm through esophageal hiatus • 2 Esophogeal sphincters: – upper esophageal sphincter – lower esophageal sphincter • Histology highlights – mucosa – submucosa: lots of mucous glands – muscularis externa – adventitia (no serosa) • Gastroesophageal Reflux • Stomach – Location • Stomach – Location: from epigastric and umbilical region • Stomach – Location: from epigastric and umbilical region to left hypochondriac regions • Gross Structural Features – cardiac region – fundus – body – pylorus – pyloric sphincter • Stomach motility video • Stomach Histology – mucosa • Stomach Histology – mucosa: location of gastric glands • Stomach Histology – mucosa: location of gastric glands • Stomach Histology – mucosa: location of gastric glands • gastric gland cells – mucous cells – parietal cells – chief cells – endocrine cells • Stomach Histology, continued – muscularis: three layers • Stomach Functions – food reservoir – formation of chyme – some chemical digestion – regulation of chyme entry into S.I. – intrinsic factor production – some absorption Digestive System, review • Basic Divisions – Digestive tract – Accessory organs: various exocrine glands • Pancreas – Location • Umbilical region • Pancreas – Location • Umbilical region • Retroperitoneal • Pancreas Gross Structure – Head – Body – Tail • Pancreas Gross Structure – Head – Body – Tail – Ducts • pancreatic • accessory – pancreas histology • mostly glandular epithelium – exocrine pancreas – endocrine pancreas – exocrine pancreas • functions – sodium bicarbonate – digestive enzymes – endocrine pancreas • structure: thousands of islets of Langerhans – endocrine pancreas • function: hormone secretion – glucagon – insulin – somatostatin • Liver –Location: epigastric and right hypochondriac regions • Liver –Location: epigastric and right hypochondriac regions • Liver –Gross structure: 2 major lobes separated by the falciform ligament • Liver Blood Supply – Hepatic portal vein – Hepatic arteries • Liver Histology – Functional unit: • Liver Histology – Functional unit: liver lobule • Liver Histology – Functional unit: liver lobule • Liver Histology – Functional unit: liver lobule – Liver cells • Liver Histology – Functional unit: liver lobule – Liver cells • hepatocytes • Kupffer cells – Each liver lobule supplied by branches of: • hepatic arteries • hepatic portal veins – Liver Functions • Maintains blood glucose levels • Cholesterol synthesis • HDL and LDL synthesis • Plasma protein synthesis – Liver Functions, continued • Hormone and drug removal • Phagocytosis • Vitamin storage • Iron storage • Bilirubin excretion – Liver Functions, continued • Hormone and drug removal • Phagocytosis • Vitamin storage • Iron storage • Bilirubin excretion – Liver Functions, continued • Hormone and drug removal • Phagocytosis • Vitamin storage • Iron storage • Bilirubin excretion • Bile salt secretion • Gall Bladder – Location: right lumbar region • Liver Blood Supply – Hepatic portal vein – Hepatic arteries • Gross Structural Features of Gall Bladder – Muscular sac – Mucosa folded into rugae – Bile enters and leaves through cystic duct • Gall Bladder Function – Stores and concentrates bile – Contracts during meals to force bile into SI • Biliary Pathway • Biliary Pathway: “plumbing” which drains bile • Small Intestine – 1 inch diameter – 10-20 ft. in length • duodenum (10 in) • jejunum (3-6 ft.) • ileum (6-12 ft) • Features of SI mucosa – Plica circularis • Features of SI mucosa – Plica circularis • Features of SI mucosa –Plica circularis –Villi • Features of SI mucosa –Plica circularis –Villi • Features of SI mucosa –Plica circularis –Villi • Features of SI mucosa –Plica circularis –Villi –Microvilli • Features of SI mucosa –Plica circularis –Villi –Microvilli • Features of SI mucosa, cont’d –Epithelial cell types: •absorptive cells •Goblet cells •Endocrine cells •Paneth cells • Features of SI mucosa, cont’d –MALT in lamina propria • Features of SI mucosa, cont’d –MALT in lamina propria • Features of SI mucosa, cont’d –MALT in lamina propria –Intestinal glands (“crypts”) • Features of SI submucosa –Submucosal glands in duodenum • Motility of SI –Segmentation movements –Peristalsis • Functions of small intestine – Completion of chemical digestion • “brush-border” enzymes required – Absorption – Endocrine control of some digestive processes Summary movie • Large Intestine • Large Intestine (large bowel) • Large Intestine (large bowel) –2.5 inches in diameter • 5-6 feet long –Cecum –Colon • Ascending • Transverse • Descending • Sigmoid –Rectum –Anal canal • Features of LI mucosa – no villi – numerous intestinal glands – goblet and absorptive cells in epithelium – MALT in lamina propria • Structural Features of cecum and colon – Taeniae coli – Haustra – Epiploic appendages • Other Structural Features – Vermiform appendix • Other Structural Features – Vermiform appendix • Other Structural Features – Vermiform appendix – Ileocecal valve • Other Structural Features – Vermiform appendix – Ileocecal valve • Other Structural Features – Vermiform appendix – Ileocecal valve – Stretch receptors in rectum • initiate defecation reflex • Other Structural Features – Vermiform appendix – Ileocecal valve – Stretch receptors in rectum • initiate defecation reflex – Anal sphincters of anal canal • Motility of Large Intestine – From cecum to transverse colon: • peristalsis – From transverse colon to rectum: • mass movements • Functions of Large Intestine – Water and electrolyte absorption – Feces formation – Defecation • Large Intestinal Bacteria – Coat surface of mucosa – Examples: E. coli – Keep out pathogenic bacteria 48