Digestion, Absorption, Transport
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Transcript of Digestion, Absorption, Transport
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
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
Digestive System Digestive System AnatomyAnatomy
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
Peritoneum and Peritoneum and MesenteriesMesenteries
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
Digestive Tract Digestive Tract HistologyHistology
Oral CavityOral Cavity 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
TeethTeeth
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
Tooth structure:Tooth structure:
Salivary GlandsSalivary Glands 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
Pharynx and EsophagusPharynx and Esophagus
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
Phases of Deglutition Phases of Deglutition (Swallowing)(Swallowing)
Deglutition Deglutition (Swallowing)(Swallowing)
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
FunctionsFunctions 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
Stomach Anatomy:Stomach Anatomy:
OpeningsOpenings GastroesophaGastroesopha
gealgeal: To : To esophagusesophagus
PyloricPyloric: To : To duodenumduodenum
RegionsRegions CardiacCardiac FundusFundus BodyBody PyloricPyloric
Stomach Anatomy Stomach Anatomy cont.cont.
RugaeRugae: Folds in stomach when empty: Folds in stomach when empty Gastric pitsGastric pits: Openings for gastric glands: Openings for gastric glands
Contain cellsContain cells Surface mucous: MucusSurface mucous: Mucus Mucous neck: Mucus Mucous neck: Mucus Parietal: Hydrochloric acid and intrinsic factor Parietal: Hydrochloric acid and intrinsic factor Chief: Pepsinogen Chief: Pepsinogen Endocrine: Regulatory hormonesEndocrine: Regulatory hormones
Stomach Histology:Stomach Histology: 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
Phases of Gastric Activity Phases of Gastric Activity I I
Hydrochloric Acid Hydrochloric Acid ProductionProduction
Phases of Gastric Activity Phases of Gastric Activity II II
Movements in StomachMovements in Stomach
Phases of Gastric Activity Phases of Gastric Activity III III
Gastric hormones:Gastric hormones:
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
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
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
Accessory Glands and Accessory Glands and StructuresStructures
LiverLiver Gall bladderGall bladder
Exocrine PancreasExocrine Pancreas Pancreatic ductPancreatic duct
Hepatic Portal SystemHepatic Portal System
Duodenum and Duodenum and PancreasPancreas
Duct SystemDuct System
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
LiverLiver 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
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
BileBile
Bile acidBile acid PhospholipidsPhospholipids CholesterolCholesterol BilirubinBilirubin Waste productsWaste products ElectrolytesElectrolytes MucinMucin
…each day around 600 ml of bile is produced…
Blood and Bile FlowBlood and Bile Flow
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
Exocrine PancreasExocrine Pancreas – – EnzymesEnzymes
TrypsinogenTrypsinogen ChymotrysinogenChymotrysinogen CarboxypeptidasesCarboxypeptidases Pro-elastasePro-elastase PhospholipasePhospholipase pancreatic lipasepancreatic lipase Pancreatic amylasePancreatic amylase Enzymes that reduce DNA and Enzymes that reduce DNA and
ribonucleic acidribonucleic acid
Bicarbonate Ion Bicarbonate Ion ProductionProduction
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
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
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))
Histology of Large Histology of Large IntestineIntestine
Transport and Secretion Transport and Secretion by Large Intestineby Large Intestine
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
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
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:
Effects of AgingEffects of Aging
Decrease in mucus layer, connective Decrease in mucus layer, connective tissue, muscles and secretionstissue, muscles and secretions
Increased susceptibility to infections Increased susceptibility to infections and toxic agentsand toxic agents Ulcerations and cancersUlcerations and cancers
Atherosclerosis is an Inflammatory Atherosclerosis is an Inflammatory DiseaseDisease
Ross R. N Engl J Med 1999;340:115-126.
EndotheliumEndothelium
Vessel LumenVessel Lumen
IntimaIntimaFoam CellFoam Cell
MonocyteMonocyte
CytokinesCytokines
Growth FactorsGrowth FactorsMetalloproteinasesMetalloproteinases
Cell ProliferationCell ProliferationMatrix DegradationMatrix Degradation MacrophageMacrophage
Lipoprotein Classes and Lipoprotein Classes and InflammationInflammation
Doi H et al. Circulation 2000;102:670-676; Colome C et al. Atherosclerosis 2000;149:295-302; Cockerill GW et al. Arterioscler Thromb Vasc Biol 1995;15:1987-1994.
HDLHDLLDLLDLChylomicrons,Chylomicrons,VLDL, and VLDL, and
their catabolic their catabolic remnantsremnants
> 30 nm> 30 nm 20–22 nm20–22 nmPotentially proinflammatoryPotentially proinflammatory
9–15 nm9–15 nmPotentially anti- Potentially anti-
inflammatoryinflammatory
LDL is composed of a core of 1500 LDL is composed of a core of 1500 molecules of cholesterol enclosed in layers of molecules of cholesterol enclosed in layers of phospholipid and unesterified cholesterol phospholipid and unesterified cholesterol molecules. molecules.
A large protein called apoprotein B-100 is A large protein called apoprotein B-100 is embedded in this hydrophilic layer.embedded in this hydrophilic layer.
LDL is generated by the bodies fat-transport LDL is generated by the bodies fat-transport system via two mechanisms; the exogenous system via two mechanisms; the exogenous and the endogenous pathways. and the endogenous pathways.
Structure of LDLStructure of LDL
Murphy HC et al. Biochemistry 2000;39:9763-970.
Hydrophobic CoreHydrophobic Core of Triglyceride of Triglyceride and Cholesteryl and Cholesteryl EstersEsters
apoBapoB
Surface Surface Monolayer of Monolayer of Phospholipids Phospholipids and Free and Free CholesterolCholesterol
The exogenous pathway begins in the The exogenous pathway begins in the intestine, and commences as the dietary fats intestine, and commences as the dietary fats become packaged into lipoprotein particles become packaged into lipoprotein particles called chylomicrons. called chylomicrons.
Chylomicrons contain phospholipid, Chylomicrons contain phospholipid, cholesterol, apolipoproteins (apo), for cholesterol, apolipoproteins (apo), for example apo B48, apo A-1, apo 11, C –11 and example apo B48, apo A-1, apo 11, C –11 and apo-E. apo-E.
Chylomicrons contain phospholipid, Chylomicrons contain phospholipid, cholesterol, apolipoproteins (apo), for cholesterol, apolipoproteins (apo), for example apo B48, apo A-1, apo 11, C –11 and example apo B48, apo A-1, apo 11, C –11 and apo-E. apo-E.
Role of LDL in InflammationRole of LDL in Inflammation
Steinberg D et al. N Engl J Med 1989;320:915-924.
EndotheliumEndothelium
Vessel LumenVessel LumenLDLLDL
LDL Readily Enter the Artery Wall Where They May be ModifiedLDL Readily Enter the Artery Wall Where They May be Modified
LDLLDL
IntimaIntima
Modified LDLModified LDL
Modified LDL are ProinflammatoryModified LDL are Proinflammatory
Hydrolysis of PhosphatidylcholineHydrolysis of Phosphatidylcholineto Lysophosphatidylcholineto Lysophosphatidylcholine
Other Chemical ModificationsOther Chemical Modifications
Oxidation of LipidsOxidation of Lipidsand ApoBand ApoB
AggregationAggregation
Monocyte chemotactic protein-1
LDLLDL
LDLLDL
Modified LDL Stimulate Expression Modified LDL Stimulate Expression of MCP-1 in Endothelial Cellsof MCP-1 in Endothelial Cells
Navab M et al. J Clin Invest 1991;88:2039-2046.
EndotheliumEndothelium
Vessel LumenVessel Lumen
IntimaIntima
MonocyteMonocyte
Modified LDLModified LDL
MCP-1MCP-1
LDLLDL
LDLLDL
Differentiation of Monocytes into Differentiation of Monocytes into MacrophagesMacrophages
Steinberg D et al. N Engl J Med 1989;320:915-924.
EndotheliumEndothelium
Vessel LumenVessel Lumen
IntimaIntima
MonocyteMonocyte
Modified LDLModified LDL
Modified LDL PromoteModified LDL PromoteDifferentiation ofDifferentiation ofMonocytes intoMonocytes intoMacrophagesMacrophages
MCP-1MCP-1
MacrophageMacrophage
LDLLDL
LDLLDL
Modified LDL Induces Macrophages to Release Modified LDL Induces Macrophages to Release Cytokines That Stimulate Adhesion Molecule Cytokines That Stimulate Adhesion Molecule
Expression in Endothelial CellsExpression in Endothelial Cells
Nathan CF. J Clin Invest 1987;79:319-326.
EndotheliumEndothelium
Vessel LumenVessel LumenMonocyteMonocyte
Modified LDLModified LDL
MacrophageMacrophage
MCP-1MCP-1
AdhesionAdhesionMoleculesMolecules
CytokinesCytokines
IntimaIntima
LDLLDL
LDLLDLEndotheliumEndothelium
Vessel LumenVessel LumenMonocyteMonocyte
MacrophageMacrophage
MCP-1MCP-1
AdhesionAdhesionMoleculesMolecules
Steinberg D et al. N Engl J Med 1989;320:915-924.
Macrophages Express Receptors Macrophages Express Receptors That Take up Modified LDLThat Take up Modified LDL
Foam CellFoam Cell
Modified Modified LDL Taken LDL Taken
up by up by MacrophagMacrophag
eeIntimaIntima
LDLLDL
LDLLDLEndotheliumEndothelium
Vessel LumenVessel LumenMonocyteMonocyte
MacrophageMacrophage
AdhesionAdhesionMoleculesMolecules
Macrophages and Foam Cells Macrophages and Foam Cells Express Growth Factors and Express Growth Factors and
ProteinasesProteinases
Foam CellFoam Cell
IntimaIntimaModified Modified
LDLLDLCytokinesCytokines
Cell ProliferationCell ProliferationMatrix DegradationMatrix Degradation
Growth FactorsGrowth FactorsMetalloproteinasesMetalloproteinases
Ross R. N Engl J Med 1999;340:115-126.
MCP-1MCP-1MCP-1MCP-1
EndotheliumEndothelium
Vessel LumenVessel LumenMonocyteMonocyte
MacrophageMacrophage
MCP-1MCP-1MCP-1MCP-1AdhesionAdhesionMoleculesMolecules
The Remnants of VLDL and The Remnants of VLDL and Chylomicrons are Also Chylomicrons are Also ProinflammatoryProinflammatory
Foam CellFoam Cell
IntimaIntimaModifiedModifiedRemnantsRemnantsCytokinesCytokines
Cell ProliferationCell ProliferationMatrix DegradationMatrix Degradation
Doi H et al. Circulation 2000;102:670-676.
Growth FactorsGrowth FactorsMetalloproteinasesMetalloproteinases
Remnant LipoproteinsRemnant Lipoproteins
RemnantsRemnants
Structure of HDLStructure of HDL
Rye KA et al. Atherosclerosis 1999;145:227-238.
Hydrophobic CoreHydrophobic Core of Triglyceride of Triglyceride and Cholesteryl and Cholesteryl EstersEsters
apoA-IIapoA-II
Surface Surface Monolayer of Monolayer of Phospholipids Phospholipids and Free and Free CholesterolCholesterol
apoA-IapoA-I
LDLLDL
LDLLDL
Miyazaki A et al. Biochim Biophys Acta 1992;1126:73-80.
EndotheliumEndothelium
Vessel LumenVessel LumenMonocyteMonocyte
Modified LDLModified LDL
MacrophageMacrophage
MCP-1MCP-1AdhesionAdhesionMoleculesMolecules
CytokinesCytokines
HDL Prevent Formation of Foam HDL Prevent Formation of Foam CellsCells
IntimaIntimaHDL Promote Cholesterol HDL Promote Cholesterol EffluxEfflux
Foam Foam CellCell
LDLLDL
LDLLDL
Mackness MI et al. Biochem J 1993;294:829-834.
EndotheliumEndothelium
Vessel LumenVessel LumenMonocyteMonocyte
Modified LDLModified LDL
MacrophageMacrophage
MCP-1MCP-1AdhesionAdhesionMoleculesMolecules
CytokinesCytokines
HDL Inhibit the Oxidative Modification of HDL Inhibit the Oxidative Modification of LDLLDL
Foam Foam CellCell
HDL Promote Cholesterol HDL Promote Cholesterol EffluxEfflux
IntimaIntima
HDL HDL InhibitInhibit
OxidationOxidationof LDLof LDL
LDLLDL
LDLLDL
Cockerill GW et al. Arterioscler Thromb Vasc Biol 1995;15:1987-1994.
EndotheliumEndothelium
Vessel LumenVessel LumenMonocyteMonocyte
Modified LDLModified LDL
MacrophageMacrophage
MCP-1MCP-1AdhesionAdhesionMoleculesMolecules
CytokinesCytokines
Inhibition of Adhesion MoleculesInhibition of Adhesion Molecules
IntimaIntima
HDL InhibitHDL InhibitOxidationOxidation
of LDLof LDL
HDL Inhibit Adhesion Molecule HDL Inhibit Adhesion Molecule ExpressionExpression
Foam Foam CellCell
HDL Promote Cholesterol HDL Promote Cholesterol EffluxEfflux
Macrophage Functions in Macrophage Functions in AtherogenesisAtherogenesis
Activation