Anatomía del sistema digestivo
Transcription
Anatomía del sistema digestivo
SISTEMA DIGESTIVO SISTEMA DIGESTIVO: bioreactores SISTEMA DIGESTIVO Es un tubo abierto: extensión del medio ambiente! S E absorción Digestión: •mecánica (trituración) •química (enzimas hidrolíticas) Sistema de Tubos y Esfínteres - Direccionalidad - Compartimentalización - Almacenamiento. EL TRACTO DIGESTIVO Anatomía del sistema digestivo Digestive tract Accessory organs Alimentary tract or canal GI tract Primarily glands Regions Mouth or oral cavity Pharynx Esophagus Stomach Small intestine Large intestine Anus Cavidad oral Mouth or oral cavity Lips (labia) and cheeks Palate: Oral cavity roof Vestibule: Space between lips or cheeks and alveolar processes Oral cavity proper Hard and soft Palatine tonsils Tongue: Involved in speech, taste, mastication, swallowing Dientes Dientes Two sets Primary, deciduous, milk: Childhood Permanent or secondary: Adult (32) Types Incisors, canine, premolar and molars Glándulas salivales Produce saliva Prevents bacterial infection Lubrication Contains salivary amylase Breaks down starch Three pairs Parotid: Largest Submandibular Sublingual: Smallest Producción de saliva - 99.5 % agua - HCO3- , ph 6.5 - moco, enzimas SECRECIONES SALIVALES 1. Secreción serosa: amilasa salival: hidrólisis a-1-4 polisacáridos 2. Secreción mucosa: lubrica y protege. 3. IgA y lisozima: antimicrobiana Reflejo de deglución Fase voluntaria Fase refleja Fase refleja Bolo alimenticio desde boca a faringe Apertura del esófago, cierre de laringe Transporte por esófago 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 Histología del tracto digestivo Estómago Openings Gastroesophageal: To esophagus Pyloric: To duodenum Regions Cardiac Fundus Body Pyloric Histología del estómago Layers Serosa or visceral peritoneum: Outermost Muscularis: Three layers Outer longitudinal Middle circular Inner oblique Submucosa Mucosa Gastric pits and glands: Contain cells Surface mucous: Mucus Mucous neck: Mucus Parietal: Hydrochloric acid and intrinsic factor Chief: Pepsinogen Endocrine: Regulatory hormones Secreción de HCl en células parietales Barrera mucus – HCO3 Pepsinógeno: proenzima Fases de la secreción gástrica FASE CEFÁLICA - percepción sensorial del alimento FASE GÁSTRICA - presencia del alimento Ondas de mezcla FASE INTESTINAL VIP Gastrin Duodeno y Pancreas Pancreas Anatomy Endocrine Exocrine Pancreatic islets produce insulin and glucagon 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 Secreción de HCO3- Enzimas Trypsinogen Chymotrysinogen Carboxypeptidases Pro-elastase Phospholipase pancreatic lipase Pancreatic amylase Hígado Lobes Major: Left and right Minor: Caudate and quadrate Ducts Common hepatic Cystic From gallbladder Common bile Joins pancreatic duct at hepatopancreatic ampulla Conductos Histología del hígado triada portal Figure 24.20a, b Bile production Hepatocytes remove ammonia and convert to urea Cholesterol and tryglicerid synthesis Gluconeogénesis, glucogénesis, glucogenólisis Phagocytosis Glycogen, fat, vitamins, copper and iron Aminoacid synthesis and degradation Salts emulsify fats, contain pigments as bilirubin Storage Funciones del hígado 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 Bilis …each day around 600 ml of bile is produced… Bile cholic acid – Na+ Phospholipids Cholesterol Waste products (Bilirubin and biliverdin, chol., drugs) Electrolytes Mucin HCO3- Intestino delgado Site of greatest amount of digestion and absorption Divisions Modifications Duodenum Jejunum Ileum: Peyer’s patches or lymph nodules Circular folds or plicae circulares, villi, lacteal, microvilli Cells of mucosa Absorptive, goblet, granular, endocrine Secreciones del int. delgado Mucus and HCO3 Enzymes Protects against digestive enzymes and stomach acids Disaccharidases Peptidases Nucleotidases, nucleosidases Enteroquinase: tripsinógeno tripsina Duodenal glands (Brünner) Stimulated by vagus nerve, secretin, chemical or tactile irritation of duodenal mucosa Duodeno llegan: quimo ácido, jugos pancreáticos, bilis Absorción intestinal Monosacáridos Lípidos Lipoproteinas Types Chylomicrons VLDL LDL Enter lymph Transports cholesterol to cells HDL Transports cholesterol from cells to liver Intestino grueso Extends from ileocecal junction to anus Consists of cecum, colon, rectum, anal canal Movements sluggish (18-24 hours) Intestino grueso: Absorción de H2O y Defecación Figure 21-27: Anatomy of the large intestine Large Intestine Cecum Colon Ascending, transverse, descending, sigmoid Rectum Blind sac, vermiform appendix attached Straight muscular tube Anal canal Internal anal sphincter (smooth muscle) External anal sphincter (skeletal muscle) Histology of Large Intestine 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 Figure 21-29: NaCl secretion by colonic crypt cells Toxina colérica - ADP-ribosilación de Ga - G-GTP AC cAMP PKA p-CFTR PKA Secreciones 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 Reflejos en Colon y Recto Secreciones del tubo digestivo Enzimas del tubo digestivo 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 Hormonas gastrointestinales Water and Ions: Water Can move in either direction across wall of small intestine depending on osmotic gradients Ions Sodium, potassium, calcium, magnesium, phosphate are actively transported Effects of Aging Decrease in mucus layer, connective tissue, muscles and secretions Increased susceptibility to infections and toxic agents Ulcerations and cancers Chemical Events in Digestion: Carbohydrates 1. Shows carbohydrate digestion. 2. Note the small intestine’s role in conversion to monoand di-saccharides. Chemical Events in Digestion: Lipids 3. Lipid digestion is shown here. 4. Note the conversion to monoglycerides in the small intestine due to bile salts and pancreatic lipase. Chemical Events in Digestion: Proteins 5. Digestion of proteins. 6. Note stomach’s conversion to polypeptides. 7. Small intestine converts to short peptides and amino acids for intestinal absorption. Gastric Secretion 1. Thin, strongly acidic (pH: 1 to 3), almost colorless liquid. It is secreted by the glands in the lining of the stomach. 2. Essential constituents are the digestive enzymes pepsin and renin, hydrochloric acid, and mucus. 3. Certain cells of the stomach lining secrete intrinsic factor which is necessary for the absorption of vitamin B12. Secretion rates of Gastric juice Path followed by bile juice in liver and gall bladder Pancreatic Secretion Production of Pancreatic Secretion Pancreatic Secretion 1. Clear, alkaline secretion of the pancreas containing enzymes that aid in the digestion of proteins, carbohydrates, and fats. 2. There are mainly two types of pancreatic secretions: - Bicarbonate Secretion, - Enzyme Secretion. Secretion of Pancreatic juice Chemistry of Digestion: Fats Figure 21-8: Fat digestion Gastric hormones: 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 Phases of Digestion: Overview Figure 21-11: Overview of functions in different regions of the digestive system Regulating Digestion: CNS and Enteric Nervous System (ENS) Figure 21-9: The enteric nervous system Cephalic and Oral Phases of Digestion Figure 21-12: Long and short reflexes in the stomach 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
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and covered with smaller folds (villi) and even smaller folds (microvilli) increase surface area for absorption to occur Site of absorption of carbohydrates, lipids, amino acids, calcium and iron...
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