SISTEMA DIGESTIVOEs un tubo abierto: extensión del medio ambiente!E S

absorción

Digestión: •mecánica (trituración)•química (enzimas hidrolíticas)

Digestion, Absorption, Digestion, Absorption, TransportTransport

DigestionDigestion Breakdown of food molecules for Breakdown of food molecules for

absorption into circulation absorption into circulation MechanicalMechanical: Breaks large food particles to : Breaks large food particles to

smallsmall ChemicalChemical: Breaking of covalent bonds by : Breaking of covalent bonds by

digestive enzymes digestive enzymes

AbsorptionAbsorption and and transporttransport Molecules are moved out of digestive tract Molecules are moved out of digestive tract

and into circulation for distribution and into circulation for distribution throughout bodythroughout body

EL TRACTO DIGESTIVO

Anatomía del sistema Anatomía del sistema digestivodigestivo

Digestive tractDigestive tract Alimentary tract or Alimentary tract or

canalcanal GI tractGI tract

Accessory Accessory organsorgans Primarily glandsPrimarily glands

RegionsRegions Mouth or oral cavityMouth or oral cavity PharynxPharynx EsophagusEsophagus StomachStomach Small intestineSmall intestine Large intestineLarge intestine AnusAnus

Histología del tracto Histología del tracto digestivodigestivo

Peritoneo y Peritoneo y mesenteriosmesenterios

PeritoneumPeritoneum VisceralVisceral: Covers organs: Covers organs ParietalParietal: Covers interior : Covers interior

surface of body wallsurface of body wall RetroperitonealRetroperitoneal: Behind : Behind

peritoneum as kidneys, peritoneum as kidneys, pancreas, duodenumpancreas, duodenum

MesenteriesMesenteries Routes which vessels Routes which vessels

and nerves pass from and nerves pass from body wall to organsbody wall to organs

Greater omentumGreater omentum Lesser omentumLesser omentum

Cavidad oral (Cavidad oral (la bouchela bouche)) Mouth or oral Mouth or oral

cavitycavity VestibuleVestibule: Space : Space

between lips or between lips or cheeks and alveolar cheeks and alveolar processesprocesses

Oral cavity properOral cavity proper Lips (labia) and Lips (labia) and

cheekscheeks PalatePalate: Oral cavity : Oral cavity

roofroof Hard and soft Hard and soft

Palatine tonsilsPalatine tonsils TongueTongue: Involved in : Involved in

speech, taste, speech, taste, mastication, mastication, swallowingswallowing

LO DIENTE!LO DIENTE!

Two setsTwo sets Primary, deciduous, Primary, deciduous,

milk: Childhoodmilk: Childhood Permanent or Permanent or

secondary: Adult secondary: Adult (32)(32)

TypesTypes Incisors, canine, Incisors, canine,

premolar and premolar and molarsmolars

Estructura dentalEstructura dental

Glándulas salivalesGlándulas salivales Produce salivaProduce saliva

Prevents bacterial Prevents bacterial infectioninfection

LubricationLubrication Contains salivary Contains salivary

amylaseamylase Breaks down starchBreaks down starch

Three pairsThree pairs Parotid: LargestParotid: Largest SubmandibularSubmandibular Sublingual: Sublingual:

SmallestSmallest

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 IgA antibodies and lysozyme, which help to destroy any microorganisms in the oral cavity.

Reflejo de deglución: Reflejo de deglución: Paladar y esófagoPaladar y esófago

Figure 21-13: The swallowing reflex

DegluciónDeglución

Three phasesThree phases VoluntaryVoluntary

Bolus of food moved by tongue from oral Bolus of food moved by tongue from oral cavity to pharynxcavity to pharynx

PharyngealPharyngealReflexReflex: Upper esophageal sphincter : Upper esophageal sphincter

relaxes, elevated pharynx opens the relaxes, elevated pharynx opens the esophagus, food pushed into esophagusesophagus, food pushed into esophagus

EsophagealEsophageal ReflexReflex: Epiglottis is tipped posteriorly, : Epiglottis is tipped posteriorly,

larynx elevated to prevent food from larynx elevated to prevent food from passing into larynxpassing into larynx

Faringe y esófagoFaringe y esófago

PharynxPharynx NasopharynxNasopharynx Oropharynx: Oropharynx:

Transmits food Transmits food normallynormally

Laryngopharynx: Laryngopharynx: Transmits food Transmits food normallynormally

EsophagusEsophagus Transports food from Transports food from

pharynx to stomachpharynx to stomach Passes through Passes through

esophageal hiatus esophageal hiatus (opening) of (opening) of diaphragm and ends diaphragm and ends at stomachat stomach

Hiatal herniaHiatal hernia SphinctersSphincters

UpperUpper LowerLower

FuncionesFunciones IngestionIngestion: Introduction of food into stomach: Introduction of food into stomach MasticationMastication: Chewing: Chewing PropulsionPropulsion

Deglutition: SwallowingDeglutition: Swallowing Peristalsis: Moves material through digestive Peristalsis: Moves material through digestive

tracttract

Y LLEGAMOS AL Y LLEGAMOS AL ESTÓMAGO!ESTÓMAGO!

OpeningsOpenings GastroesophaGastroesopha

gealgeal: To : To esophagusesophagus

PyloricPyloric: To : To duodenumduodenum

RegionsRegions CardiacCardiac FundusFundus BodyBody PyloricPyloric

Histología del Histología del estómago:estómago:

LayersLayers Serosa or visceral Serosa or visceral

peritoneum: peritoneum: OutermostOutermost

Muscularis: Three Muscularis: Three layerslayers

Outer longitudinalOuter longitudinal Middle circularMiddle circular Inner oblique Inner oblique

SubmucosaSubmucosa MucosaMucosa

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.

Producción de HClProducción de HCl

Protección contra la Protección contra la acidez: el MOCOacidez: el MOCO

Figure 21-15: The mucus-bicarbonate barrier of the gastric mucosa

Movements in StomachMovements in Stomach

Small IntestineSmall Intestine Site of greatest Site of greatest

amount of digestion amount of digestion and absorptionand absorption

Divisions Divisions DuodenumDuodenum JejunumJejunum Ileum: Peyer’s patches Ileum: Peyer’s patches

or lymph nodulesor lymph nodules ModificationsModifications

Circular folds or plicae Circular folds or plicae circulares, villi, lacteal, circulares, villi, lacteal, microvillimicrovilli

Cells of mucosaCells of mucosa Absorptive, goblet, Absorptive, goblet,

granular, endocrinegranular, endocrine

Movement in small Movement in small intestine:intestine:

Mixing: Segmental contraction that occurs in small Mixing: Segmental contraction that occurs in small intestineintestine

Secretion: Lubricate, liquefy, digestSecretion: Lubricate, liquefy, digest Digestion: Mechanical and chemicalDigestion: Mechanical and chemical Absorption: Movement from tract into circulation or lymphAbsorption: Movement from tract into circulation or lymph Elimination: Waste products removed from bodyElimination: Waste products removed from body

Small Intestine Small Intestine SecretionsSecretions

MucusMucus Protects against digestive enzymes and Protects against digestive enzymes and

stomach acidsstomach acids Digestive enzymesDigestive enzymes

Disaccharidases: Break down disaccharides Disaccharidases: Break down disaccharides to monosaccharidesto monosaccharides

Peptidases: Hydrolyze peptide bondsPeptidases: Hydrolyze peptide bonds Nucleases: Break down nucleic acidsNucleases: Break down nucleic acids

Duodenal glandsDuodenal glands Stimulated by vagus nerve, secretin, chemical Stimulated by vagus nerve, secretin, chemical

or tactile irritation of duodenal mucosaor tactile irritation of duodenal mucosa

Duodenum Anatomy Duodenum Anatomy and Histologyand Histology

Large Intestine:Large Intestine:

Extends from ileocecal junction to anusExtends from ileocecal junction to anus Consists of cecum, colon, rectum, anal canalConsists of cecum, colon, rectum, anal canal Movements sluggish (Movements sluggish (18-24 hours18-24 hours))

Large IntestineLarge Intestine

CecumCecum Blind sac, vermiform appendix attachedBlind sac, vermiform appendix attached

ColonColon Ascending, transverse, descending, sigmoidAscending, transverse, descending, sigmoid

RectumRectum Straight muscular tubeStraight muscular tube

Anal canalAnal canal Internal anal sphincter (smooth muscle) Internal anal sphincter (smooth muscle) External anal sphincter (skeletal muscle) External anal sphincter (skeletal muscle) Hemorrhoids: Vein enlargement or inflammationHemorrhoids: Vein enlargement or inflammation

Secretions of Large Secretions of Large IntestineIntestine

Mucus provides protectionMucus provides protection Parasympathetic stimulation increases rate Parasympathetic stimulation increases rate

of goblet cell secretionof goblet cell secretion PumpsPumps

Exchange of bicarbonate ions for chloride Exchange of bicarbonate ions for chloride ionsions

Exchange of sodium ions for hydrogen ionsExchange of sodium ions for hydrogen ions Bacterial actions produce gases called Bacterial actions produce gases called

flatusflatus

Movement in Large Movement in Large IntestineIntestine

Mass movementsMass movements Common after mealsCommon after meals

Local reflexesLocal reflexes in enteric plexus in enteric plexus GastrocolicGastrocolic: Initiated by stomach: Initiated by stomach DuodenocolicDuodenocolic: Initiated by duodenum: Initiated by duodenum

Defecation reflexDefecation reflex Distension of the rectal wall by fecesDistension of the rectal wall by feces

DefecationDefecation Usually accompanied by voluntary movements to Usually accompanied by voluntary movements to

expel feces through abdominal cavity pressure expel feces through abdominal cavity pressure caused by inspirationcaused by inspiration

Reflexes inReflexes in Colon and Colon and Rectum:Rectum:

Intestinal Phase: Intestinal Phase: Large Intestine, HLarge Intestine, H22O Absorption O Absorption

& Defecation& Defecation

Figure 21-27: Anatomy of the large intestine

Intestinal Phase: Intestinal Phase: Large Intestine Digestion & Large Intestine Digestion &

AbsorptionAbsorption

Figure 21-28: NaCl reabsorption by colonocytes

Bacterial Bacterial fermentationfermentation: Vit. K , : Vit. K , lactate & lactate & buteratebuterate

Water and Water and electrolyte electrolyte secretion secretion &/or &/or absorptionabsorption

Intestinal Phase: Intestinal Phase: Large Intestine Digestion Large Intestine Digestion

& Absorption& Absorption

Figure 21-29: NaCl secretion by colonic crypt cells

Phases of Digestion: Phases of Digestion: OverviewOverview

Figure 21-11: Overview of functions in different regions of the digestive system

Regulating Digestion: CNS Regulating Digestion: CNS and Enteric Nervous and Enteric Nervous

System (ENS)System (ENS)

Figure 21-9: The enteric nervous system

Digestión: fases oral y Digestión: fases oral y cefálicacefálica

Figure 21-12: Long and short reflexes in the stomach

Digestive System Digestive System RegulationRegulation

Nervous regulationNervous regulation Involves enteric Involves enteric

nervous systemnervous system Types of neurons: Types of neurons:

sensory, motor, sensory, motor, interneuronsinterneurons

Coordinates Coordinates peristalsis and peristalsis and regulates local regulates local reflexesreflexes

Chemical regulationChemical regulation Production of Production of

hormoneshormones Gastrin, secretinGastrin, secretin

Production of Production of paracrine chemicalsparacrine chemicals

Histamine Histamine Help local reflexes in Help local reflexes in

ENS control digestive ENS control digestive environments as pH environments as pH levels levels

Gastric hormones:Gastric hormones:

LO QUE MATA ES EL LO QUE MATA ES EL HÍGADOHÍGADO

LobesLobes MajorMajor: Left and right: Left and right MinorMinor: Caudate and : Caudate and

quadratequadrate DuctsDucts

Common hepaticCommon hepatic CysticCystic

From gallbladderFrom gallbladder Common bileCommon bile

Joins pancreatic duct Joins pancreatic duct at hepatopancreatic at hepatopancreatic ampullaampulla

Funciones del hígadoFunciones del hígado Bile productionBile production

Salts emulsify fats, contain pigments as bilirubinSalts emulsify fats, contain pigments as bilirubin

StorageStorage Glycogen, fat, vitamins, copper and ironGlycogen, fat, vitamins, copper and iron

Nutrient interconversionNutrient interconversion DetoxificationDetoxification

Hepatocytes remove ammonia and convert to ureaHepatocytes remove ammonia and convert to urea

PhagocytosisPhagocytosis Kupffer cells phagocytize worn-out and dying red and Kupffer cells phagocytize worn-out and dying red and

white blood cells, some bacteriawhite blood cells, some bacteria

SynthesisSynthesis Albumins, fibrinogen, globulins, heparin, clotting factorsAlbumins, fibrinogen, globulins, heparin, clotting factors

Blood and Bile FlowBlood and Bile Flow

Duct SystemDuct System

BileBile

Bile acidBile acid PhospholipidsPhospholipids CholesterolCholesterol BilirubinBilirubin Waste productsWaste products ElectrolytesElectrolytes MucinMucin

…each day around 600 ml of bile is produced…

Functions of the LiverFunctions of the Liver Bile productionBile production

Salts emulsify fats, contain pigments as bilirubinSalts emulsify fats, contain pigments as bilirubin

StorageStorage Glycogen, fat, vitamins, copper and ironGlycogen, fat, vitamins, copper and iron

Nutrient interconversionNutrient interconversion DetoxificationDetoxification

Hepatocytes remove ammonia and convert to ureaHepatocytes remove ammonia and convert to urea

PhagocytosisPhagocytosis Kupffer cells phagocytize worn-out and dying red and Kupffer cells phagocytize worn-out and dying red and

white blood cells, some bacteriawhite blood cells, some bacteria

SynthesisSynthesis Albumins, fibrinogen, globulins, heparin, clotting factorsAlbumins, fibrinogen, globulins, heparin, clotting factors

GallbladderGallbladder

Bile is stored and concentratedBile is stored and concentrated Stimulated by cholecystokinin and Stimulated by cholecystokinin and

vegal stimulationvegal stimulation Dumps into small intestineDumps into small intestine Production of gallstones possibleProduction of gallstones possible

Drastic dieting with rapid weight lossDrastic dieting with rapid weight loss

Duodenum and Duodenum and PancreasPancreas

PancreasPancreas

AnatomyAnatomy EndocrineEndocrine

Pancreatic islets Pancreatic islets produce insulin and produce insulin and glucagon glucagon

ExocrineExocrine Acini produce Acini produce

digestive enzymesdigestive enzymes RegionsRegions: Head, : Head,

body, tailbody, tail

SecretionsSecretions Pancreatic juice Pancreatic juice

(exocrine)(exocrine) TrypsinTrypsin ChymotrypsinChymotrypsin CarboxypeptidaseCarboxypeptidase Pancreatic amylasePancreatic amylase Pancreatic lipasesPancreatic lipases Enzymes that Enzymes that

reduce DNA and reduce DNA and ribonucleic acidribonucleic 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 Bicarbonate Ion ProductionProduction

Exocrine PancreasExocrine Pancreas – – EnzymesEnzymes

TrypsinogenTrypsinogen ChymotrysinogenChymotrysinogen CarboxypeptidasCarboxypeptidas

eses Pro-elastasePro-elastase PhospholipasePhospholipase pancreatic lipasepancreatic lipase Pancreatic Pancreatic

amylaseamylase

LipoproteinsLipoproteins

TypesTypes ChylomicronsChylomicrons

Enter lymphEnter lymph VLDLVLDL LDLLDL

Transports Transports cholesterol to cellscholesterol to cells

HDLHDL Transports Transports

cholesterol from cholesterol from cells to livercells to liver

Water and Ions:Water and Ions:

WaterWater Can move in either Can move in either

direction across wall direction across wall of small intestine of small intestine depending on osmotic depending on osmotic gradientsgradients

IonsIons Sodium, potassium, Sodium, potassium,

calcium, magnesium, calcium, magnesium, phosphate are actively phosphate are actively transportedtransported

Chemistry of Digestion: Chemistry of Digestion: FatsFats

Figure 21-8: Fat digestion