SISTEMA DIGESTIVO

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

2. Digestion, Absorption, Transport • Digestion • Breakdown of food molecules for absorption into circulation • Mechanical: Breaks large food particles to small • Chemical: Breaking of covalent bonds by digestive enzymes • Absorption and transport • Molecules are moved out of digestive tract and into circulation for distribution throughout body

3. EL TRACTO DIGESTIVO

4. 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

5. Histología del tracto digestivo

6. Peritoneo y mesenterios • 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

7. Cavidad oral (la bouche) • 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

8. LO DIENTE! • Two sets • Primary, deciduous, milk: Childhood • Permanent or secondary: Adult (32) • Types • Incisors, canine, premolar and molars

9. Estructura dental

10. Glándulas salivales • Produce saliva • Prevents bacterial infection • Lubrication • Contains salivary amylase • Breaks down starch • Three pairs • Parotid: Largest • Submandibular • Sublingual: Smallest

12. Producción de saliva

13. Tipos de saliva1. 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.

14. Reflejo de deglución: Paladar y esófago Figure 21-13: The swallowing reflex

15. Deglución • 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

16. 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 Faringe y esófago

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

18. Y LLEGAMOS AL ESTÓMAGO! • Openings • Gastroesophageal: To esophagus • Pyloric: To duodenum • Regions • Cardiac • Fundus • Body • Pyloric

19. Histología del estómago: • Layers • Serosa or visceral peritoneum: Outermost • Muscularis: Three layers • Outer longitudinal • Middle circular • Inner oblique • Submucosa • Mucosa

21. Gastric Secretion • Thin, strongly acidic (pH: 1 to 3), almost colorless liquid. It is secreted by the glands in the lining of the stomach. • Essential constituents are the digestive enzymes pepsin and renin, hydrochloric acid, and mucus. • Certain cells of the stomach lining secrete intrinsic factor which is necessary for the absorption of vitamin B12.

22. Producción de HCl

23. Protección contra la acidez: el MOCO Figure 21-15: The mucus-bicarbonate barrier of the gastric mucosa

27. Movements in Stomach

29. 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

30. Movement in small intestine: • Mixing: Segmental contraction that occurs in small intestine • Secretion: Lubricate, liquefy, digest • Digestion: Mechanical and chemical • Absorption: Movement from tract into circulation or lymph • Elimination: Waste products removed from body

31. 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

32. Duodenum Anatomy and Histology

33. Large Intestine: • Extends from ileocecal junction to anus • Consists of cecum, colon, rectum, anal canal • Movements sluggish (18-24 hours)

34. Large Intestine • Cecum • Blind sac, vermiform appendix attached • Colon • Ascending, transverse, descending, sigmoid • Rectum • Straight muscular tube • Anal canal • Internal anal sphincter (smooth muscle) • External anal sphincter (skeletal muscle) • Hemorrhoids: Vein enlargement or inflammation

35. Secretions of Large Intestine • Mucus provides protection • Parasympathetic stimulation increases rate of goblet cell secretion • Pumps • Exchange of bicarbonate ions for chloride ions • Exchange of sodium ions for hydrogen ions • Bacterial actions produce gases called flatus

36. Movement in Large Intestine • Mass movements • Common after meals • Local reflexes in enteric plexus • Gastrocolic: Initiated by stomach • Duodenocolic: Initiated by duodenum • Defecation reflex • Distension of the rectal wall by feces • Defecation • Usually accompanied by voluntary movements to expel feces through abdominal cavity pressure caused by inspiration

37. Reflexes in Colon and Rectum:

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

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

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

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

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

43. Digestión: fases oral y cefálica Figure 21-12: Long and short reflexes in the stomach

44. Nervous regulation Involves enteric nervous system Types of neurons: sensory, motor, interneurons Coordinates peristalsis and regulates local reflexes Chemical regulation Production of hormones Gastrin, secretin Production of paracrine chemicals Histamine Help local reflexes in ENS control digestive environments as pH levels Digestive System Regulation

46. Gastric hormones:

47. LO QUE MATA ES EL HÍGADO • Lobes • Major: Left and right • Minor: Caudate and quadrate • Ducts • Common hepatic • Cystic • From gallbladder • Common bile • Joins pancreatic duct at hepatopancreatic ampulla

48. Funciones del hígado • 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

49. Blood and Bile Flow

50. Duct System