1. SISTEMA DIGESTIVO

3. SISTEMA DIGESTIVO: bioreactores

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

5. Sistema de Tubos y Esfínteres
Direccionalidad
Compartimentalización
Almacenamiento.

6. EL TRACTO DIGESTIVO

7. 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

8. Cavidad oral Mouth or oral cavity Lips (labia) and cheeks
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

9. Dientes

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

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

13. Producción de saliva
% agua
HCO3- , ph 6.5
moco, enzimas

14. SECRECIONES SALIVALES 1. Secreción serosa: amilasa salival:
hidrólisis a-1-4 polisacáridos
Secreción mucosa:
lubrica y protege.
IgA y lisozima:
antimicrobiana

15. Reflejo de deglución Fase voluntaria Fase refleja Fase refleja
Bolo alimenticio desde boca a faringe
Fase refleja
Apertura del esófago,
cierre de laringe
Fase refleja
Transporte por esófago

16. Histología del tracto digestivo

17. 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

18. Estómago Openings Regions 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

22. Gastric pits and glands:
Contain cells
Surface mucous: Mucus
Mucous neck: Mucus
Parietal: Hydrochloric acid and intrinsic factor
Chief: Pepsinogen
Endocrine: Regulatory hormones

23. Secreción de HCl en células parietales

24. Barrera mucus – HCO3-

25. Fases de la secreción gástrica

26. FASE CEFÁLICA
- percepción sensorial del alimento

27. FASE GÁSTRICA
- presencia del alimento

28. Ondas de mezcla

29. FASE INTESTINAL
VIP
Gastrin

31. Duodeno y Pancreas

32. Pancreas Anatomy Secretions Endocrine Pancreatic juice (exocrine)
Pancreatic islets produce insulin and glucagon
Exocrine
Acini produce digestive enzymes and HCO3-
Regions: Head, body, tail
Secretions
Pancreatic juice (exocrine)
Trypsin
Chymotrypsin
Carboxypeptidase
Pancreatic amylase
Pancreatic lipases
Elastase
Nucleases (DNA, RNA)
HCO3-, H20

35. Secreción de HCO3-

36. Enzimas Trypsinogen Chymotrysinogen Carboxypeptidases Pro-elastase
Phospholipase
pancreatic lipase
Pancreatic amylase
Pancreatic juice is composed of two secretory products critical to proper digestion: digestive enzymes and bicarbonate. The enzymes are synthesized and secreted from the exocrine ascinar cells, whereas bicarbonate is secreted from the epithelial cells lining small pancreatic ducts.
Digestive Enzymes
The pancreas secretes a magnificent battery of enzymes that collectively have the capacity to reduce virtually all digestible macromolecules into forms that are capable of, or nearly capable of being absorbed. Three major groups of enzymes are critical to efficient digestion:
Proteases
Digestion of proteins is initiated by pepsin in the stomach, but the bulk of protein digestion is due to the pancreatic proteases. Several proteases are synthesized in the pancreas and secreted into the lumen of the small intestine. The two major pancreatic proteases are trypsin and chymotrypsin, which are synthesized and packaged into secretory vesicles as an the inactive proenzymes trypsinogen and chymotrypsinogen.
As you might anticipate, proteases are rather dangerous enzymes to have in cells, and packaging of an inactive precursor is a way for the cells to safely handle these enzymes. The secretory vesicles also contain a trypsin inhibitor which serves as an additional safeguard should some of the trypsinogen be activated to trypsin; following exocytosis this inhibitor is diluted out and becomes ineffective - the pin is out of the grenade.
Once trypsinogen and chymotrypsinogen are released into the lumen of the small intestine, they must be converted into their active forms in order to digest proteins. Trypsinogen is activated by the enzyme enterokinase, which is embedded in the intestinal mucosa.
Once trypsin is formed it activates chymotrypsinogen, as well as additional molecules of trypsinogen. The net result is a rather explosive appearance of active protease once the pancreatic secretions reach the small intestine.
Trypsin and chymotrypsin digest proteins into peptides and peptides into smaller peptides, but they cannot digest proteins and peptides to single amino acids. Some of the other proteases from the pancreas, for instance carboxypeptidase, have that ability, but the final digestion of peptides into amino acids is largely the effect of peptidases in small intestinal epithelial cells. More on this later.
Pancreatic Lipase
The major form of dietary fat is triglyceride, or neutral lipid. A triglyceride molecule cannot be directly absorbed across the intestinal mucosa. Rather, it must first be digested into a 2-monoglyceride and two free fatty acids. The enzyme that performs this hydrolysis is pancreatic lipase, which is delivered into the lumen of the gut as a constituent of pancreatic juice.
Sufficient quantities of bile salts must also be present in the lumen of the intestine in order for lipase to efficiently digest dietary triglyceride and for the resulting fatty acids and monoglyceride to be absorbed. This means that normal digestion and absorption of dietary fat is critically dependent on secretions from both the pancreas and liver.
Pancreatic lipase has recently been in the limelight as a target for management of obesity. The drug orlistat (Xenical) is a pancreatic lipase inhibitor that interferes with digestion of triglyceride and thereby reduces absorption of dietary fat. Clinical trials support the contention that inhibiting lipase can lead to significant reductions in body weight in some patients.
Amylase
The major dietary carbohydrate for many species is starch, a storage form of glucose in plants. Amylase is the enzyme that hydrolyses starch to maltose (a glucose-glucose disaccharide), as well as the trisaccharide maltotriose and small branchpoints fragments called limit dextrins. The major source of amylase in all species is pancreatic secretions, although amylase is also present in saliva of some animals, including humans.
Other Pancreatic Enzymes
In addition to the proteases, lipase and amylase, the pancreas produces a host of other digestive enzymes, including ribonuclease, deoxyribonuclease, gelatinase and elastase.
Bicarbonate and Water
Epithelial cells in pancreatic ducts are the source of the bicarbonate and water secreted by the pancreas. The mechanism underlying bicarbonate secretion is essentially the same as for acid secretion parietal cells and is dependent on the enzyme carbonic anhydrase. In pancreatic duct cells, the bicarbonate is secreted into the lumen of the duct and hence into pancreatic juice.

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

39. Histología del hígado
triada
portal
Figure 24.20a, b

40. Funciones del hígado Bile production Storage Aminoacid synthesis
Salts emulsify fats, contain pigments as bilirubin
Storage
Glycogen, fat, vitamins, copper and iron
Aminoacid synthesis
Cholesterol and tryglicerid synthesis
Gluconeogénesis, glucogénesis, glucogenólisis
Hepatocytes remove ammonia and convert to urea
Phagocytosis
Kupffer cells phagocytize worn-out and dying red and white blood cells, some bacteria
Plasma proteins and hemostatic factors
Albumins, globulins, fibrinogen, heparin, K vitamin
Detoxification and drug metabolism
Hormonal secretion: trombopoietin, angotensinogen

41. …each day around 600 ml of bile is produced…
Bilis
…each day around 600 ml of bile is produced…
Bile acid
Phospholipids
Cholesterol
Bilirubin
Waste products
Electrolytes
Mucin
HCO3-

42. Conductos

43. Intestino delgado 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

44. Secreciones del int. delgado
Mucus and HCO3-
Protects against digestive enzymes and stomach acids
Enzymes
Disaccharidases
Peptidases
Nucleotidases, nucleosidases
Enteroquinase: tripsinógeno  tripsina
Duodenal glands (Brünner)
Stimulated by vagus nerve, secretin, chemical or tactile irritation of duodenal mucosa

45. Duodeno llegan: quimo ácido, jugos pancreáticos, bilis

46. Absorción intestinal

47. Monosacáridos

48. Lípidos

49. Lipoproteinas Types Chylomicrons VLDL LDL HDL Enter lymph
Transports cholesterol to cells
HDL
Transports cholesterol from cells to liver

50. Intestino grueso Extends from ileocecal junction to anus
Consists of cecum, colon, rectum, anal canal
Movements sluggish (18-24 hours)

51. Intestino grueso: Absorción de H2O y Defecación
Figure 21-27: Anatomy of the large intestine

52. Large Intestine Cecum Colon Rectum Anal canal
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)

53. Histology of Large Intestine

54. Figure 21-28: NaCl reabsorption by colonocytes
Water and electrolyte secretion &/or absorption
Bacterial fermentation of HC
Bacterial synthesis of Vit. K , B.
Bacterial degradation of bile acids and esterols
Absortion of lactate & butyrate
Prevents infections and immune alterations
Figure 21-28: NaCl reabsorption by colonocytes

55. Figure 21-29: NaCl secretion by colonic crypt cells

56. Toxina colérica ADP-ribosilación de Ga
 G-GTP  AC  cAMP  PKA  p-CFTR
PKA

57. Secreciones Mucus provides protection Pumps
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

58. Reflejos en Colon y Recto

59. Secreciones del tubo digestivo

60. Enzimas del tubo digestivo

61. Regulación nerviosa y hormonal
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

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

64. Hormonas gastrointestinales