physiology gi 1
TRANSCRIPT
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PHYSIOLOGY
GI SYSTEM
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Food composition
Proximateprinciples
Carbohydrates
Lipids
Proteins
Water
Otheressential components
Vitamins
Minerals
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Food composition
Carbohydrates
Lipids
Proteins
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Total Energy Requirement
Basal Metabolic rate+
Typeofwork
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Basal Metabolic Rate
BMR isthetotalnumberofcalories body requiresfor
normal bodilyfunctions (excluding activityfactors).
Thisincludes keeping heart beating, inhaling andexhaling
air, digesting food, making new blood cells, maintaining
bodytemperatureandeveryothermetabolic processin
the body.
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CalculateBMR
Harris-Benedictformula (BMR basedontotal body weight)
Men BMR = 66 + (13.7 X wtin kg)+ (5 X htin cm)- (6.8 X ageinyears)
Women
BMR = 655 + (9.6 X wtin kg)+ (1.8 X htin cm)- (4.7 X ageinyears)
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Activity Multiplier
1. Sedentary = BMR X 1.2 (littleornoexercise, desk job)
2. Lightlyactive = BMR X 1.375 (lightexercise/sports 1-3 days/wk)
3. Mod.active = BMR X 1.55 (moderateexercise/sports 3-5days/wk)
4. Veryactive = BMR X 1.725 (hardexercise/sports 6-7days/wk)
5. Extr.active = BMR X 1.9 (harddailyexercise/sports & physicaljob or2X daytraining, i.emarathon, contestetc.)
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Whatisyourobjective?
Fatloss : - 500
Maintenance : Keepsame
Weight gain: + 500
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Digestion
Digestionisaprocess wherebythe complexfood
materialis brokentosimplerformssothatit can
beabsorbedandutilized bythe body.
Food
material
Simpler
forms
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FunctionsofdigestivesystemFunctionsofdigestivesystemFunctionsofdigestivesystemFunctionsofdigestivesystem
Ingestion: getting foodintothe GI tract (eating)
Propulsion- moving foodalong thetracte.g.
swallowing andperistalsis (wave-likemotion)
Secretion: keysubstanceslikeacidetc
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FunctionsofdigestivesystemFunctionsofdigestivesystemFunctionsofdigestivesystemFunctionsofdigestivesystem
Mechanicaldigestion- physical grinding and
churning offoodstuffsto breakdownand
exposetoenzymesandthesurfaceofthe GI
tract
Chemicaldigestion- breakdownoflarger
moleculesintoabsorbableparts byenzymaticaction
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FunctionsofdigestivesystemFunctionsofdigestivesystemFunctionsofdigestivesystemFunctionsofdigestivesystem
Absorption- transportofdigestedmolecules,
vitamins, minerals, water, into blood
Defecation- eliminationofunusedfoodstuff
(feces)
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Four Major LayersofGI Tract
1. Mucosa
2. Submucosa
3. Muscularis
4. Serosa
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FourmajorlayersofGI Tract
Mucosa
Innermostlayer, whichlinesthelumen
Functionsincludeabsorption, secretion
Consistsofepithelium, typicallysimple columnar, often withgoblet cells
Submucosa
Deeptothemucosa
Madeupofconnectivetissue containing bloodandlymphatic vessels, lymphoidnodules, andnervefibres
Providesvascularsupplytomoststructuresofthe GI tractwall
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Four Major LayersofGI Tract
Muscularismucosa
Deeptothesubmucosa
Smoothmusclelayer responsibleforperistalsisandsegmentation
Aninner circularlayerandanouterlongitudinallayer
Serosa
Outermostlayeroftheintraperitonealorgans
Also know asthevisceralperitoneum
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PartsofD
igestivesystemKey parts
Mouth
Pharynx
Esophagus
Stomach
Small intestine Large intestine
Anus
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PartsofD
igestivesystem
Accessory organs
Teeth
Tongue
Salivary glands
Gallbladder Liver
Pancreas
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Mouth, Pharynx,
Esophagus
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Teeth
Humans usually have 20 primary teeth (also called deciduous,baby, or milk teeth) and 32 permanent teeth. Among primaryteeth, 10 are found in the (upper) maxilla and the other 10 in the
(lower) mandible.
Teeth are classified as incisors, canines, and molars.
In the primary set of teeth, there are two types of incisors,
centrals and laterals, and two types of molars, first and second.
All primary teeth are replaced with permanent counterpartsexcept for molars, which are replaced by permanent premolars.
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Teeth
Among permanent teeth, 16 are found in the maxilla with theother 16 in the mandible.
Central incisor
Lateral incisor Canine
First premolar
Second premolar
First molar
Second molar
Third molar: wisdom teeth
If any additional teeth form, for example, fourth and fifth molars,which are rare, they are referred to as supernumerary teeth.
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Teeth
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Salivary Glands
Threepairsofsalivary
glandssecretesalivainto
theoral cavity, where itismixed withfoodduring
mastication.
Parotid
Sub-mandibular
Sublingual
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CompositionofSaliva
Water (97-99.5%)
Electrolytes: Na+, K+, Cl-
Mucin- proteinthatformsthick, slimy
mucus
Salivaryamylase- starts breakdownof
carbohydrates
Other: IgAantibodies, Lysozyme
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Tongue
Coating ofsensors (dorsalsurface)fortaste, heat, pain,andtactileinformation
Muscularorgan
Tonguemusclesinsidethetongue, whichmakeupmostofthetonguemass, includethe Lingualisinferior,superior, transverse, andvertical.
Tonguemuscleslike Styloglossus, the Hyoglossus,Palatoglossus, Pharyngoglossus, and Genioglossusbeginoutsidethetongue withonlyterminalfibersinsideit, and controlitsmovement.
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Mechanical Processes
Mastication (chewing)
Cheeks, tongue, andteethinvolvedin both
voluntaryandinvoluntary grinding and
tearing offoodstuffs
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Mechanical Processes
Deglutition (swallowing)
Buccalphase (voluntary) Bolusforcedintooropharynx bytongue
Pharyngeal-esophagealphase (involuntary)
Tongue blocksoffmouth, softpalate blocksoff
nasopharyxandepiglottis blocksofftrachea Foodpropelledintoesophagus
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Roleofesophagus
Esophagus
Movesfoodtothestomach by Peristalsis
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Ifchewing notpossible
Rylestubefeeding
Parenteralfeeding: IVfluids
Gastrostomyfeeds: feedingtubethroughtheskinandthe
stomach wall, directlyintothestomach.
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Collectinformation
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Roleofstomach
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Gastric Movements
Proper
digestion
requires
coordinated
movements
ofthe
stomachandintestines
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Gastric Movements
Loweresophagealsphincter (LES /Cardiac sphincter)
Junctionofesophagusandthestomach
Mainfunctionofthesphincteristhepreventionof
refluxfromthestomachintotheesophagus.
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Gastric Movements
Peristalsis: Theperistaltic waves beginhighupon
thefundus, aboutthreetimesaminuteandpassinggentlytowardsthepylorus. Peristalsishelpsin
propelling thefoodahead.
Churning: Processofmixing offood
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Gastric Movements
Pyloric Sphincter (Pylorus)
Junctionofstomachandduodenum
Thedistinctivefeaturesofthepylorusisverynarrow
lumen whichensuresthatonlysmallsizeparticlesleavethestomach.
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Gastric Movements
Gastric emptying
Gastric emptying requires coordination between
theantralperistaltic wavesandduodenalmotility
toensureefficientmovementofthenutrientsinto
theduodenum.
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ACID SECRETION
AT A GLANCE
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Acidsecretion
Typesofsecretoryepithelial cellsinstomach
Mucous cells
Parietal cells
Chiefcells
G cells
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Acidsecretion
Typesofsecretoryepithelial cellsinstomach
Mucous cells Secreteanalkalinemucusthat
protectstheepitheliumagainstshearstressandacid
Parietal cells Secretehydrochloric acid
Chiefcells Secretepepsin, aproteolytic enzyme
G cells Secretethehormone gastrin
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Stimulusforacid release
Histamine Acetyl choline Gastrin
Parietal cell
Acid release
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Stepsinacidsecretion
STEP 1: Hydrogenionsare generated withinthe
parietal cellfromdissociationofwater. Thehydroxylionsformedinthisprocess rapidly
combine with carbondioxidetoform bicarbonate
ion, a reaction cataylzed by carbonic anhydrase.
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Stepsinacidsecretion
STEP 2: Bicarbonateistransportedoutofthe
basolateralmembraneinexchangefor chloride.
ThisprocessservestomaintainintracellularpH
intheparietal cell.
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Stepsinacidsecretion
STEP 3: Chlorideandpotassiumionsaretransportedintothelumenofthe cannaliculus byconductance channels, whichisnecessaryforsecretionofacid.
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Stepsinacidsecretion
STEP 4: Hydrogenionispumpedoutofthecell, intothelumen, inexchangeforpotassiumthroughtheactionoftheprotonpump;potassiumisthuseffectively recycled.
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Gastric
lumen
Basolateral
Membrane
Histamine Acetyl cholineGastrin
Parietal
cell H2O + CO2= H+ + HCO3-
K+
HCO3-
Cl-
Cl-H+
Cl-
H+K+ ATPase (Protonpump)
HCO3-
Cl-
H+K+
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Acidsecretion
Fasting stomachsecretes gastric juiceatthe rateof10-60 mlperhour (Basal Output).
Mealtimesecretionof500 mlto 1000 ml- startsimmediatelyafterfood; reachesitsmaximumafter 1 to2hours, and graduallydeclinestofasting levelafter 3 to 4 hours. (Maximal Output).
Gastric juiceisacidic;itspH ranges between 0.9 to1.5.
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Canstomach bearthisacid?
Theepitheliumofthestomachisintrinsically resistant
tothedamaging effectsofgastric acidandotherinsults.
+
Mucinproduction (Protective)
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Neurological controlof GIT
Autonomic
nervoussystem
Parasympathetic nerves
Sympathetic nerves
Enteric nervous
system
Nervoussystemofgastrointestinal
tract
Central control Centers withinthemedullaoblongata
Higher brain centers
Gastrointestinalmotilityandsecretionsare
controlled bythenerves withinthe GIT.
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Autonomic Nervous System
Parasympathetic nerves: Role
Stimulationofnerve causessmoothmusclecontractionandthesecretionofdigestive juices.
Sympathetic nerves: Role
Reducessmoothmuscle contractionand
glandularsecretion.
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Enteric Nervous System
Liesentirelyinthe wallofthe gastro-intestinaltract,
beginning intheesophagusandextending allthe
waytotheanus.
Control
Movements
Control
Secretions
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Roleof Neurotransmitters
Acetylcholinemostoftenexcites gastrointestinal
activity.
Norepinephrinealwaysinhibits gastrointestinal
activity.
Other keyneurotransmittersin GIT include
dopamine.
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Thank You.