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FISIOLOGIA DIGESTIVA FISIOLOGÍA DIGESTIVA (BCM II) Clase 11: Digestión y absorción de nutrientes Dr. Michel Baró Aliste © 2003 Science Press Internet Services Nutrients provided by animal and vegetable products © 2003 Science Press Internet Services Digestive process is initiated by sensory signals © 2003 Science Press Internet Services The effect of discussion, sight, and smell of food © 2003 Science Press Internet Services Oral cavity has important functions in initial processing TABLE 2 - 4. DIGESTION STARTS IN THE ORAL CAVITY Mastication–Mechanical disruption of solid food Increased salivary secretion–Moistening of food particles and mixing with salivary amylase, R - factors, and lingual lipase Taste of food–Increased stimulation of gastric secretion Swallowing of food bolus © 2003 Science Press Internet Services The arrival of a swallowed food bolus in the stomach © 2003 Science Press Internet Services The emptying of food from the stomach © 2003 Science Press Internet Services Passage of acidic, hyperosmolar gastric chyme into duodenum © 2003 Science Press Internet Services Cholecystokinin and secretin are of major importance © 2003 Science Press Internet Services Macronutrient digestion and absorption proceed at rapid pace 95% © 2003 Science Press Internet Services Large bowel: role in carbohydrate digestion and absorption © 2003 Science Press Internet Services The primary bile acids, cholic and chenic acid Recirculación entero-hepática de las sales biliares: dos veces por cada comida. © 2003 Science Press Internet Services Lipids have highest energy content of 3 macronutrients a-grasos esenciales: ac.linoleico ac.linolénico © 2003 Science Press Internet Services The initial event in lipid digestion in the stomach Formación de gotas de emulsión pH 4-5,5 © 2003 Science Press Internet Services Lipid digestion proceeds at a rapid pace in duodenum © 2003 Science Press Internet Services Bile acids are amphipaths © 2003 Science Press Internet Services Transport of lipolytic products © 2003 Science Press Internet Services The lipolytic products are resynthesized acetil-coA © 2003 Science Press Internet Services End products of lipid absorption in the enterocytes © 2003 Science Press Internet Services Carbohydrate is the major energy source in the diet 400 g/día Endoglucosidasas +sucrosa +lactosa © 2003 Science Press Internet Services Products of starch digestion and two dietary disaccharides © 2003 Science Press Internet Services Glucose, galactose, and fructose are not lipid soluble © 2003 Science Press Internet Services Protein digestion begins in the stomach © 2003 Science Press Internet Services Average daily protein intake is about 70-100 g in adults © 2003 Science Press Internet Services The proteolytic enzymes secreted by pancreatic acini © 2003 Science Press Internet Services Oligopeptides and amino acids generated by intraluminal proteolysis TABLE 2 - 25. BRUSH - BORDER OLIGOPEPTIDE HYDROLYSIS Brush - Border Enzymes Substrate Products Enteropeptidase Trypsinogen Trypsin Endopeptidase 24.11 Hydrophobic AA Peptides Neutral endopeptidase ? Peptides Neutral AA Neutral AA Endopeptidases Exopeptidases Aminopeptidase N Di - and tripeptides Aminopeptidase A Acidic AA Acidic AA Dipeptidylpeptidase IV Penultimate proline Dipeptides Gly - Leu peptidase Dipeptide (Aliphatic) AA Asp - Lys peptidase Dipeptide (Basic) AA Folate Conjugase Polyglutamated Folates Folic Acid © 2003 Science Press Internet Services Proteolytic enzymes are secreted in vast excess by pancreas bás. bás. arom. neut. alif. © 2003 Science Press Internet Services Dipeptides, tripeptides, and amino acids © 2003 Science Press Internet Services Amino acid transport systems TABLE 2 - 28. AMINO ACID TRANSPORT SYSTEMS IN ENTEROCYTES Brush Border Basolateral Membrane Amino Acid Specificity Sodium Coupled A A Neutral + ASC ASC Neutral + B Neutral + BO,+ Neutral + Neutral - Proline + Branched AA - Asp, Glut + Arg, Lys - bO,+ bO,+ Imino L L XY+AG Y+ © 2003 Science Press Internet Services Vitamin B12 is one of water-soluble vitamins © 2003 Science Press Internet Services Folate is present in food, primarily in polyglutamate form (exopeptidasa) (hidrosolubles) © 2003 Science Press Internet Services Daily intake of 3 major minerals in the diet © 2003 Science Press Internet Services Trace elements are important constituents of diet TABLE 2 - 32. TRACE ELEMENT ABSORPTION Daily Intake, MG Amount Absorbed, % Zinc 10 - 15 20 - 50 Copper 1-3 30 - 70 Selenium 0.1 - 0.2 ? Manganese 2 - 5 15 - 25 Uptake processes of trace elements are poorly defined–presumably both carrier - mediated transport and passive diffusion play a role. © 2003 Science Press Internet Services Fin © 2003 Science Press Internet Services
