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SISTEMA DIGESTIVO

SISTEMA DIGESTIVO. Es un tubo abierto: extensión del medio ambiente!. S. E. absorción. Digestión: mecánica (trituración) química (enzimas hidrolíticas). EL TRACTO DIGESTIVO. Anatomía del sistema digestivo. Digestive tract Alimentary tract or canal GI tract Accessory organs

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SISTEMA DIGESTIVO

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  1. SISTEMA DIGESTIVO Es un tubo abierto: extensión del medio ambiente! S E absorción • Digestión: • mecánica (trituración) • química (enzimas hidrolíticas)

  2. EL TRACTO DIGESTIVO

  3. Anatomía del sistema digestivo • Digestive tract • Alimentary tract or canal • GI tract • Accessory organs • Primarily glands • Regions • Mouth or oral cavity • Pharynx • Esophagus • Stomach • Small intestine • Large intestine • Anus

  4. Oral Cavity • Mouth or oral cavity • Vestibule: Space between lips or cheeks and alveolar processes • Oral cavity proper • Lips (labia) and cheeks • Palate: Oral cavity roof • Hard and soft • Palatine tonsils • Tongue: Involved in speech, taste, mastication, swallowing

  5. Teeth • Two sets • Primary, deciduous, milk: Childhood • Permanent or secondary: Adult (32) • Types • Incisors, canine, premolar and molars

  6. Tooth structure:

  7. Salivary Glands • Produce saliva • Prevents bacterial infection • Lubrication • Contains salivary amylase • Breaks down starch • Three pairs • Parotid: Largest • Submandibular • Sublingual: Smallest

  8. Production of Salivary juice

  9. SALIVARY SECRETIONS1. Serous secretion that contains ptyalin, which is an enzyme for digesting starches. 2. Mucous secretion that contains mucin for lubricating and for surface protective purposes. 3. Saliva also contains IgA antibodies and lysozyme, which help to destroy any microorganisms in the oral cavity.

  10. Swallowing reflex: Soft Palate & Esophagus Figure 21-13: The swallowing reflex

  11. Deglutition (Swallowing) • Three phases • Voluntary • Bolus of food moved by tongue from oral cavity to pharynx • Pharyngeal Reflex: Upper esophageal sphincter relaxes, elevated pharynx opens the esophagus, food pushed into esophagus • Esophageal • Reflex: Epiglottis is tipped posteriorly, larynx elevated to prevent food from passing into larynx

  12. Histología del tracto digestivo

  13. Peritoneum and Mesenteries • Peritoneum • Visceral: Covers organs • Parietal: Covers interior surface of body wall • Retroperitoneal: Behind peritoneum as kidneys, pancreas, duodenum • Mesenteries • Routes which vessels and nerves pass from body wall to organs • Greater omentum • Lesser omentum

  14. Pharynx Nasopharynx Oropharynx: Transmits food normally Laryngopharynx: Transmits food normally Esophagus Transports food from pharynx to stomach Passes through esophageal hiatus (opening) of diaphragm and ends at stomach Hiatal hernia Sphincters Upper Lower Pharynx and Esophagus

  15. Functions • Ingestion: Introduction of food into stomach • Mastication: Chewing • Propulsion • Deglutition: Swallowing • Peristalsis: Moves material through digestive tract

  16. Stomach Anatomy: • Openings • Gastroesophageal: To esophagus • Pyloric: To duodenum • Regions • Cardiac • Fundus • Body • Pyloric

  17. Stomach Histology: • Layers • Serosa or visceral peritoneum: Outermost • Muscularis: Three layers • Outer longitudinal • Middle circular • Inner oblique • Submucosa • Mucosa

  18. Stomach Histology • Rugae: Folds in stomach when empty • Gastric pits: Openings for gastric glands • Contain cells • Surface mucous: Mucus • Mucous neck: Mucus • Parietal: Hydrochloric acid and intrinsic factor • Chief: Pepsinogen • Endocrine: Regulatory hormones

  19. Hydrochloric Acid Production

  20. Gastric Phase: The Stomach Figure 21-15: The mucus-bicarbonate barrier of the gastric mucosa

  21. Phases of Gastric Secretion

  22. Movements in Stomach

  23. Small Intestine • Site of greatest amount of digestion and absorption • Divisions • Duodenum • Jejunum • Ileum: Peyer’s patches or lymph nodules • Modifications • Circular folds or plicae circulares, villi, lacteal, microvilli • Cells of mucosa • Absorptive, goblet, granular, endocrine

  24. Small Intestine Secretions • Mucus • Protects against digestive enzymes and stomach acids • Digestive enzymes • Disaccharidases: Break down disaccharides to monosaccharides • Peptidases: Hydrolyze peptide bonds • Nucleases: Break down nucleic acids • Duodenal glands • Stimulated by vagus nerve, secretin, chemical or tactile irritation of duodenal mucosa

  25. Duodenum Anatomy and Histology

  26. Duodenum and Pancreas

  27. Large Intestine, H2O Absorption & Defecation Figure 21-27: Anatomy of the large intestine

  28. Large Intestine Digestion & Absorption • Bacterial fermentation: Vit. K , lactate & butyrate • Water and electrolyte secretion &/or absorption Figure 21-28: NaCl reabsorption by colonocytes

  29. Intestinal Phase: Large Intestine Digestion & Absorption Figure 21-29: NaCl secretion by colonic crypt cells

  30. Phases of Digestion: Overview Figure 21-11: Overview of functions in different regions of the digestive system

  31. Regulating Digestion: CNS and Enteric Nervous System (ENS) Figure 21-9: The enteric nervous system

  32. Cephalic and Oral Phases of Digestion • Cephalic: anticipation of food • CNS  ANS long reflex • Enteric  cells short reflex • GI motility • GI secretions • Mouth: starts digestion • Grind, mix & liquefy • Saliva: water, enzymes, mucus & lysozyme

  33. Cephalic and Oral Phases of Digestion Figure 21-12: Long and short reflexes in the stomach

  34. Liver • Lobes • Major: Left and right • Minor: Caudate and quadrate • Ducts • Common hepatic • Cystic • From gallbladder • Common bile • Joins pancreatic duct at hepatopancreatic ampulla

  35. Functions of the Liver • Bile production • Salts emulsify fats, contain pigments as bilirubin • Storage • Glycogen, fat, vitamins, copper and iron • Nutrient interconversion • Detoxification • Hepatocytes remove ammonia and convert to urea • Phagocytosis • Kupffer cells phagocytize worn-out and dying red and white blood cells, some bacteria • Synthesis • Albumins, fibrinogen, globulins, heparin, clotting factors

  36. Blood and Bile Flow

  37. Duct System

  38. Gallbladder • Bile is stored and concentrated • Stimulated by cholecystokinin and vegal stimulation • Dumps into small intestine • Production of gallstones possible • Drastic dieting with rapid weight loss

  39. Anatomy Endocrine Pancreatic islets produce insulin and glucagon Exocrine Acini produce digestive enzymes Regions: Head, body, tail Secretions Pancreatic juice (exocrine) Trypsin Chymotrypsin Carboxypeptidase Pancreatic amylase Pancreatic lipases Enzymes that reduce DNA and ribonucleic acid Pancreas

  40. Bicarbonate Ion Production

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