SISTEMA DIGESTIVO Es un tubo abierto extensin del

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

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

EL TRACTO DIGESTIVO

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

Histología del tracto digestivo

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

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

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

Estructura dental

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

Producción de saliva

Tipos de saliva 1. 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 Ig. A antibodies and lysozyme, which help to destroy any microorganisms in the oral cavity.

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

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

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

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

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

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

Gastric Secretion 1. Thin, strongly acidic (p. H: 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 B 12.

Producción de HCl

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

Movements in Stomach

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

Movement in small intestine: n n n 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

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

Duodenum Anatomy and Histology

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

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

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

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

Reflexes in Colon and Rectum:

Large Intestine, H 2 O Absorption & Defecation Figure 21 -27: Anatomy of the large intestine

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

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

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

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

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

Gastric hormones:

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

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

Blood and Bile Flow

Duct System

Bile …each day around 600 ml of bile is produced… n n n n Bile acid Phospholipids Cholesterol Bilirubin Waste products Electrolytes Mucin

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

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

Duodenum and Pancreas

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

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.

Bicarbonate Ion Production

Exocrine Pancreas – Enzymes n n n n Trypsinogen Chymotrysinogen Carboxypeptidases Pro-elastase Phospholipase pancreatic lipase Pancreatic amylase

Lipoproteins n Types n Chylomicrons n n n VLDL n n Enter lymph Transports cholesterol to cells HDL n Transports cholesterol from cells to liver

Water and Ions: n Water n n Can move in either direction across wall of small intestine depending on osmotic gradients Ions n Sodium, potassium, calcium, magnesium, phosphate are actively transported

Chemistry of Digestion: Fats Figure 21 -8: Fat digestion