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PHYSIOLOGY OF THE GI TRACT

Peter C A Kam

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FUNCTION OF THE GI TRACT

1. Ingestion Motility mechanical breakdown offood, propulsion of food through gut

2. Digestion Secretion secretion of enzymes,water & ions

3. Absorption

Control of motility and secretion bynervous system and hormones

4. Egestion

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Properties of GI smooth muscle

5-10m

200mForm hollow tubes not contracting against skeletonForm a syncitium electrically couple, joined by gap junction contractions

synchronousActin:myosin ratio 15:1 (skeletal muscle 2:1)Contractile elements not arranged in sarcomeres not striatedStimulated by neurotransmitter released from varicositiesHave slow wave activity.

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0

Me

Acetylcholine

M e m

b r a n e

P o

t e n t i a

l ( m V )

Tension

Tension

0

-60

0

-60

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Slow waves in GI smooth muscle

Slow waves are changes in resting membrane potential IE 3-12 cycles per minute depending on area of GI tract 3/min in

stomach, 12/min small intestine. Always present but do not always cause contractions. Frequency of contractions dictated by frequency of slow waves. Slow wave frequency and height modulated by body temp &

metabolic activityIntrinsic & extrinsic nerves (increased by Ach, SP; decreased bynoradrenaline, No. VIP). Circulating hormones (esp. CCK,motilin)

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Myosin (PO 4)2

Calcium activates contraction

OUT Depends on influx of calciumfrom extracellular space

IN Ca 2 through calcium channels

Calcium-calmodulin complexactivates myosin light chainkinase

(Ca 2)4-CalmodulinContraction explained bysliding filament theory

Inactive myosin Active myosin lightlight chain kinase chain kinase

MUSCLECONTRACTION

Contraction of GI smooth muscle

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Innervation of the GI tract

2. Extrinsic nervesParasympathetic innervation

- Via preganglionic fibres in vagus and pelvic nerves- Synapse on ganglionic neurons in enteric nervous system- Excitatory through release of acetylcholine

Parasympathetic nervous system- Postganglionic fibres from coeliac, superior and inferior

mesenteric system.- Inhibitory through release of noradrenaline

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Parasympathetic n.s. Sympathetic n.s.

Vagal nuclei CNSPreganglionic Fibres

Preganglionic fibres

Sacral spinal Sympathetic

cord gangliaPostganglionic fibres

Enteric nervous SystemMyenteric Submucosal

plexus plexus

Smooth Secretory Endocrine BloodMuscle cells cells vessels

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Effect of different stimuli on

muscle contractionStimulus Effect on muscle

more depolarised smooth

1. Stretch of GI tract wall muscle, more excitable 2. Acetylcholine release Leads toaction potential 3. Parasympathetic stimulation generation and smooth

muscle contraction.

4. Noradrenaline release more hyperpolarised smooth5. Sympathetic stimulation muscle, Less excitable and

fewer contractions .

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Musculature of the GI tract

All smooth muscle except :

Upper third of oesophagus striatedMiddle third of oesophagus mixedExternal anal sphincter striated

Areas of striated muscle are areas thatare under conscious control .

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GASTRIN

3 Main forms polypeptides

II G34 - T = 15 minsIII G17 T = 2-3minsIV G14I G45V G 4

Produced by G cells in Antral part and duodenal bulb.

Physiological Actions

Gastric AcidGastrin Pepsin

Also insulin + glucagon after a mealGastric motility ++Gastro-oesophageal sphincter.

Release

Amino Acids LuminalPeptides Acids

Distention of SecretinStomach G Cell GlucagonVagus Gastric Inh

PeptidesCatecholamine Intestinal inh.

Peptides

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CHOLECYSTOKININ - PANCREOZYMIN

SECRETED BY UPPER SMALL INTESTINE

STRUCTUREAmino Acids CCK 39, 33, 12, 8, 4C5 terminal amino acids similar to Gastrin

ACTIONS1. Gall Bladder contraction2. Pancreatic juice - rich in enzymes3. INHIBIT gastric emptying4. Augments pyloric sphincter tone to delay gastric emptying5. Enterokinase Secretion6. Augments action of secretion

7. Glucagon

SECRETION Peptides / amino acid in intestineFA > 10 carbon in duodenum

+ve feed back with protein or fat digestion

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SECRETIN

Produced by small intestineAmino acid structure glucagonT = 5 mins.

Action HCO 3- Pancreatic Juice

Water Content

Augments CCK actionGastric HClInsulin secretion

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GIP

43 amino - residuesSecretion duodenum + jejunumStimulated by glucose + fat in duodenum

ACTION - insulin SecretionInhibit gastric motility + secretion

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VIP

28 amino acidT 2 mins.In blood + gutStimulates Electrolytes & H2O of intestinal secretions.Dilate blood vessels

Gastric acid secretion

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GI motility

There are many types of contractions in differentAreas of the GI tract. Some muscles contract and

relax in seconds

- phasic contractions peristalsissegmentation

Some maintain contractions over minutes or hours

- tonic contractions sphincters.

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GI motility controlled by both humoral and neuralMechanisms1. Extrinsic nervous systemParaymp = acetylcholine release = increased contraction

2. Intrinsic nervous systemReceptors in GI tract/stretch = Ach, SP release = increased contraction

3. Hormones

Only hormones known to have physiological effects on motility are

motilin = increased gastric and intestinal motilitycholecystokinin = decreased gastric emptying

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Gastric motility

Fundus acts as food storeBody and antrum mix food 1. Relaxtion of fundusPylorus contracts to limit exit of chyme (vagovagal reflex

3. Pylorus contracts

4. Mixing byretropulsion

2.Contractionof bodyand antrum

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Slow waves in the stomach cause

contraction without action potential

Em

Tension

4s

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Control of gastric motility

Vagovagal reflex - Fundal relaxationMyenteric plexus - Slow waves

contractions

Parasympathetic - inc contraction forceand freq

Sympathetic - dec contraction forceand freq

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Control of gastric emptying

Chyme only empties from stomach when particle size is smallEnough to pass through polyrus

Most important mechanism is strong stomach contractions

Contractions stimulated by :

1. Presence of food

2. Gastrin

But control of stomach emptying by these factor is fairly weak

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solids

liquids

Time

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Control of gastric emptying

Most control of stomach emptying is done throughInhibitory mechanisms in the duodenum and jejunumThrough nervous reflexes and hormones

Inhibitory reflexes - direct - myenteric plexusindirect via extrinsic nervesNeural reflexes stimulated by :Distension, irritation, acidity, high osmolality,Protein/fat.Fats and acids also stimulate release of humoral factors whichReduce gastric emptyingCholecystokinin stim. By fatsSecretin stim. By acids.

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Gastric motility on fasting

Migrating Motor Complex Occurs on fasting I.e. after digestion and absorption of last meal, toclear undigested food particles.

Peristatic contractions sweep down stomach and duodenum pylorus relaxes.

Pattern of contraction approx every 90 min. on fasting

Slow peristatic waves sweeping whole of GI tract

Thought to be controlled by motilin

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Control of intestinal motility- neuronal

Mixing segmentationfrequency set by slow waves (12/minute dudenum)additional control myeneteric plexus

Propulsion peristalsisLocal reflex stretch causes relaxation distal andcontraction proximal ( Bayliss-Starling law of the intestines)moves bolus through intestines.

Intestino-intestinal reflex extrinsic nervesLocal stretch in one area inhibits contractions in rest of bowel

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Reflex control of gut activity

CNS

Parasympathetic andSympathetic efferents Parasympathetic

and sympatheticSplanchnic efferent

And vagalAfferents Myenteric Submucosal

plexus plexus

Local efferentsLocal afferents

Gut wall muscleChemoreceptors Endocrine cellsmechanoreceptors in Secretory cellsgut wall Blood vessel

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Na + low Na + high

K+

diffusion Na + ATP

Na + Cl-

Na + also absorbedIn active transportProcesses eg

Glucose, aminoAcids, H + ions Osmosis H2O

Aldosterone stimulates Na + absorption

Absorption of electrolytes and water

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Disorder of fluid absorption

consequence - diarrhoea

Hyperosmotic chyme e.g. high intake of

artificial sugars or high acid content. Infection e.g. cholera

Colon can absorb 7L water per day but if smallIntestine secretes more than this, result isDiarrhoea.

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Reflex Stimulus Effect

gastroenteric Stomach distension Sl activitygastrocolic Distension,emptying Colonicduodenocolic distension motility

enterogastric Chyme stomachacid/protein/fat emptyingirritant

vagovagal Food in stomach Fundal relax.intestointestinal distention relaxation

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Clinical problems with motilityGastric emptying

too slow = gastric carcinoma orulceration (vagotomy)

Results in nausea and vomiting, diarrhoea, cramps.Patients seek help for difficulty swallowing (oesophageal scarring)or dental erosion.

too fast = usually found in patients with

duodenal ulcer

Dont know if cause or effect overwhelms protective defences ofduodenum

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VOLUME OF G.I.T. SECRETIONS

Saliva 1000mlGastric Juice 3000mlPancreatic Juice 1000mlBile 1000mlIntestinal Juice 3000ml

TOTAL 9000ml

DAILY EXCRETION OF ELECTROLYTESIN GIT SECRETIONS

Na K Cl

Saliva 200 10 100Gastric J 150 20 250Pancreatic J 70 3 50Bile 100 4 50Intestinal J 300 15 300

Mmol/day 820 52 750

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GASTRIC SECRETION

William Beaumont first identified actions of gastricJuice, hydrochloric acid content, mucus secretion,and observed gastric motility directly in 1825.

Protection of mucosamucusbicarbonate

Digestion and absorption of food, control of motilityacid gastrinpepsinogen cholecystokeninintrinsic factor histamine

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Oxyntic gland mucosasecretesmucusacid from parietal cellsPepsinogen from pepticcellsIntrinsic factor from

parietal cells in humans(peptic cells in otherspecies.

Endocrine cells

Pyloric gland mucosa secretes throughout mucosasecretesmucushistaminegastrin from G cells

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Gastric secretions Mucus

Physical/ChemicalpH

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Parietal cell - secretingTubulovesicles fuse withcanaliculus, increased surface area

and numbers of H +K+ATP aseincreases acid secretion into lumenof gut.

H+Acid secretion is against a 3million fold concentrationgradientH+ inside = 4x 10 -8MH+ outside = 0.1 M

NEEDS ENERGY

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Blood Parietal cell LumenAt rest 70mV

Secretion 40mVK+ K+ HCO 3-

HCO 3- ATPH+ H+

H2CO 3Na + Na +

ATP H2O + CO 2 Na + Na +

K+ K+ ATP

Cl- Cl - Cl -

ATP

H2O H2O

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Na +K+

Cl -

H+

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Gastric secretions

Pepsinogen Inactive precursor of pepsin whichinitiates protein digestion

Is not necessary for completedigestion of dietary protein pancreatic enzymes are sufficient

active only when the pH < 3.5Released by Ach

Pesinogen pepsin

Acid

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Gastric secretions

Intrinsic factor

- Secreted from parietal cells in humans, chief cell in other

Species.- Forms a complex with vitamin B 12 in the gut

- The complex is resistant to digestion & therefore enablesAbsorption of vitamin B 12

Lack of intrinsic factor causes Vit B 12 deficiency(Pernicious anaemia) as all the Vit B 12 is digested andTherefore none can be absorbed

Only gastric secretion that isEssential for health

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HCl SECRETION

CELLINTERSTITIAL JUICE

Cl Cl

CO 2 + H2Oc.A.

H2O CO 3

HCO 3- + H+

K

OH - H+

H2O

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Gastric hormones

GastrinRelease from G-cells in the pyloric glands is stimulated by Distension of stomach causes gastrin releasing

peptide (GRP) release from submucosal plexus-GRP causes gastrin release

Presence of amino acids in stomach stimulateschemoreceptors local reflexes cause gastrin release.

Release inhibited by pH

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Gastric secretionControl is in 3 phases

1. Cephalic phase entirely dependent on the vagal nerve accountsfor 10% - 15% total volume of secretion

acid secretion stimulated by sight, smell, chewing

and swallowingOral/nasal chemoreceptors vagal nucleus Ach + GRPRelease acetylcholine + gastrin + histamine = acid secretion

Vagalafferents

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2. Gastric phase accounts for at least 50% of gastricsecretion

Controlled by local reflexes, vagovagal reflexes and hormones

Distension of stomach local mechanoreceptors acetylcholineand gastrin release acid and pepsinogen secretionAmino acids/peptides local chemoreceptors gastrin release

acid and pepsinogen secretion

3. Intestinal phase - about 5% of secretion

Primarily hormonal denervated stomach will be stimulated

to secrete acid by protein in duodenumHormone still unknown

Very small number of G-cells in duodenum also release gastrin in responseto amino acids.

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Inhibition of gastric secretionAll mechanisms for the inhibition of acid secretion act to ensure effectivedigestion of food.

1. Control by the stomachFall in pH

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Secretion of the small intestine,pancreas and liver

Small Intestine

many villi on surface of intestine

crypts/glands of Lieberkuhn between villi epithelial cells havebrush border.

Secretions are from cells within the crypts of Lieberkuhn and fallInto two groups

secretions into the lumen (from enterocytes)secretions into the blood (from endocrine cells)

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Secretion into the lumen - mucus

Pancreas

First protectionFor duodenumFrom acid

Brunner s glands Compound mucus glands,Secreting

- alkali- mucus

SecretionStimulated byPara-sympathetics

Inhibited by

Sympathetics

?stress relatedulceration

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Secretions into the lumen-aqueous

Absorption of nutrients andSecretion occurs at brushBorder in matureenterocytes

Secretion moves up and outOf the crypts, mixes withChyme and washes over theVilli into the lumen

Water and electrolyteSecretion fromUndifferentiated enterocytesIn the bottom of crypts

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Intestinal secretions

Small intestineMucus/alkali secretions mucosal protection

Aqueous secretionsunder local nervous controlsome minor hormonal control (secretin, CCK)

Large intestineSecretion primarily consists of mucus. Can also secrete waterIn response to irritation

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Pancreatic secretions

Endocrine insulin & glucagonExocrine enzymes and bicarbonate

essential for digestion

almost under separate hormonal control

Key hormones in stimulation of secretion are :

Cholecystokinin (CCK)

Secretin

Both released from the small intestine

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Pancreas

Stomach

duodenum

PeptidesAmino acids, H +

FAT

I Cells

CCK

Cholecystokinin

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Pancreatic enzymes

Essential for digestion - essential for life

Acinar cells

Proteases Lipases Amylases

Inactive form

Active enzymesActivated in gut

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SECRETIN

FAT H +

HCO 3-

S cells

SECRETIN

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ATP

Bicarbonate secretionLumen Blood

H2O CO 2 CO 2

H2CO 3

HCO 3- HCO 3- H+ H+

Cl - Cl - Na + Na + Na +

H2O H 2O

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Pancreatic secretion

- secretion in 3 phasesCephalic phase - only 10-15% of total secretion

activation of vagal efferents stimulates enzymerelease

Gastric phase - only present in some speciesNOT SIGNIFICANT IN HUMANS

Intestinal phase - majority of secretioncombination of hormones CCK and secretinresults in maximal enzyme and bicarbonaterelease

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Intestinal phase of secretion

VAGUS

CCK

PeptidesAmino acids

Fat, H +

Secretin HCO 3-

Enzymes

ACH

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Functions of bile

- emulsification of facts- increased absorption of lipids into

enterocytes.

- cholesterol excretion (only route)

- excretion of breakdown products ofhaemoglobin (bilirubin)

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Secretion and storage of bile

Constituents of bileLiver Gallbladder

Water 98% 92%Bile Salts 1% 6%Bilirubin 0.04% 0.3%Cholesterol 0.1% 0.3-0.9%Fatty acids 0.12% 0.3-1.2%

Lecithin 0.04% 0.3%

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Liver Secretion

Function and fateOf bile acids - theEnterohepaticcirculation

Bile acids almost totally

Reabsorbed in terminal illeum.20% excreted daily. Inhibition ofReabsorption results inSynthesis of new bile acids andLowering of cholesterol levels.

Portal vein

Gallbladder-Storage &concentration

CommonBile duct

DuodenumDigestion &emulsification

Ileum Absorbption ofBile acids

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Secretions of the intestine, pancreasand liver-summary

Small intestine- mucus and fluid involved in protection and absorption- hormones control of pancreatic and bile secretions.

Pancreatic secretions- Bicarbonate for neutralisation of acids, optimises

conditions for enzyme action- Enzymes for digestion

Liver- bile for emulsification of fat

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Digestion of carbohydrate, protein and fats by catalytic

hydrolysis

enzymes are either luminal (e.g. from salivary glandsor pancreas) or membrane bound

Digested nutrients / fluids absorbed through the brushBorder by

active transportdiffusion passive

facilitatedsolvent drag

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Carbohydrate digestion- Initiated by salivary amylase from salivary glands- majority by pancreatic amylase in small intestine- pH optimum 7, activated by Cl - ions

1,4 bonds give straight chains

1,6 bonds give branched chains

Amylase can only hydrolyse 1,4bonds branched chains cannot be

broken down by amylase

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Carbohydrate digestion

StarchGlycogen

-dextrins, di-&trisaccharides

Glucose, galactosefructose

Luminal digestionamylase

Membrane digestione.g. sucrase, lactase

Humans do not haveCellulase-cellulose makesUp most of undigested fibreIn diet

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Absorption of simple sugars

Limiting step on simple sugar availability is rate ofAbsorption large excess in small intestine.

Majority absorbed in duodenum and jejunum

Digested at membrane so available for transport

Fructose absorbed by facilitated diffusion

Glucose/galactose absorbed passively (small quantities)Under anaerobic conditions and actively absorbed by sameCarrier when O 2 available.

Deficiencies of brush border enzymes cause osmotic diarrhoea

Human Sl can absorb up to 10kg sucrose per day

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Absorption of glucose

Na+

Na +

Glu

Glu

Glu

Na +

ATP

K+ Low Na +

Na +

diffusion

Facilitated transport

Glu

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Activation of pancreatic proteases

Enterokinases

Trypsinogen Trypsin

TrypsinogenChymotrypsinogen

ProelastaseProcarboxypeptidase

TrypsinChymotrypsin

ElastaseCarboxypeptidase

Active proteases inactivated by trypsin

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TransportersPeptidases

aminopolypeptidase Transporters

Cytoplasmic peptidase

Amino acids

Protein

PeptidesDi/tripeptides

Amino acids

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Absorption of peptides and amino acids

Transport at the brush border1. Active transport by carrier.2. Mostly dependent on Na + gradient co-transport similar to that

for glucose.3. Some amino acids (basic, and neutral with hydrophobic side

chains) are absorbed by facilitated diffusion.

Protein assimilation affected by :

Pancreatitis, congenital protease deficiencies, deficiencies of specificTransporters.

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Absorption of vitamins

Vitamin Soluble in fat Soluble in waterA B1 B2

Niacin C D E K

Folic Acid B6 B12

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Calcium absorption

Skin Vit D 3

Liver 25, OH-D 3

Kidney 1,25 (OH) 2D3

Parathyroid hormone

Ca 2

CBPCa 2+

Ca 2+

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Absorptive capacity of theintestine

Actual Capacity

500g Carbohydrate 10g100g Fat 500g

50-100g Protein 700gaminoacids

7 8L Water 20+ L

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Iron absorption transferrinmediated uptake

Fe 2+ + plasma transferrin

Ferritin

Fe Fe

Fe

Fe

Fe

Fe

TF

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Digestion and absorption

Digestion by hydrolysis Importance of pancreatic enzymes

Types of membrane bound enzymes Mechanism of absorption :

Carbohydrates, fats, proteins, electrolytes, water, special cases

Effect of disturbances in digestion / absorption.

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Nutrition and control of foodintake

Control of appetite, hunger and satietyNutritional requirements

Essential fatty acidsEssential amino acidsCarbohydratesVitamins, minerals

Special cases, pregnancy & lactationMalnutrition & dental relevance

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Experimental evidence that hungerand satiety are controlled centrally

lateral nucleus feeding centreElectrical stimulation hyperphagia

Destruction aphagia

Endogenous control of feeding

Low plasma glucose and amino acidsInput from olfactory ( smell ), gustatory ( taste ) andVisual primary afferents

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Ventromedial nucleus satiety centre

Stimulation refusal to eatDestruction uncontrolled eating, obesity

Endogenous control of feedingAlso responds to low plasma [glucose] and[amino acids] BUT IN OPPOSITE WAYOther inputs : stomach distension, plasma CCK

& insulin all stimulateAmphetamines potentiate neurotransmitter effects in the VMN andSuppress feeding

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Regulation of food intake

Glucose (GI & plasma)Amino acidsLipids (CCK)

Ventromedial nucleussatiety centre

Lateral nucleusfeeding centre

++ -

- -Feeding

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Regulation of appetite food choice

Controlled by dietary need (exp.animals) Controlled by limbic system (amygdala)

acting on hypothalamusArea of brain involved in emotional control

Lesions abolish food choice

Major control in humans (developed world)probably taste rather than dietary need,

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Long termBodyTemperature-Energyavailable

GlucostaticAminostaticlipostatic

Control of food intake

Short termWhat stops you eating

Hormones CCK,Insulin,glucagon

Gl distensionOral meter

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Nutrition what we need and why ?Amino acids protein synthesis

Essential, conditionally essential, non -essential plus Extra

Protein requirements 0.6g/kg adult per dayMore in growth & repair e.g. infants, infection, pregnancy

Protein required due to turnover in tissuesIn growth or wasting, tissues which turnover protein fastest will alter most in mass

I.e. Liver, gut, white cells

Loss of protein = loss of function

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Nutrition what we need and why

Fatty acid deficiency in animals -failure to grow linolenic acid

skin & kidney lesions

Linoleic and arachidonic acids reverseother deficiencies.

BODY CANNOT MAKE THESE FATTY ACIDSESSENTIAL

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Nutrition what we need and why

Carbohydrates- non-essential

except for non-starch polysaccarhides (fibre).

Insufficient fibre results in poor blood glucose and lipid control, increasedGut infection and incidence of cancer.

- preferred source of energy- Sucrose most cariogenic substance

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Vitamins

Deficiency becoming more common inSome urban populations in UK

Vit D - ricketsVit C - scurvy

Long history of recognised importance -Deficiency disease

e.g. beri-beri (B 1; 2000BC), scurvy(C; in sailors 1400 AD)

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Vitamins requirements and deficiencies

1. Water solubleVitamin Recommended daily intake (mg) Deficiency

B1 (Thiamine) 1.5 Beri-beriRiboflavin 1.8Niacin 20 PellagraC 45 ScurvyFolic acid 0.4 Anaemia, spina bifida

B12 0.003 Pernicious anaemiaB6 2Panthothenic acid unknown

Not stored in body deficiency leads to rapid clinical symptoms.Most important ones in terms of dentistry are :B12 (fiboflavin) important for cellular metabolism in mouth, cornea & skin

deficiency glossitis, angular stomatitis, corneal vascularisationphotophobia

Vitamin C necessary for collagen formationdeficiency (scurvy) = gingival oedema & bleeding, delayed healing,brusing.

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Vitamins requirements and deficiencies

2. Fat solubleVitamin Recommended daily intake Deficiency

A 5000 IU Blindness, dry mucous membrane, abortiongrowth failure.

D 400 IU Rickets, poorly calcified dentition, delayederuption

E 15 IU Foetal resorptionK 70 g Poor clotting

Particularly important in dentistry :Vitamin A - 500,000 new cases per year in developed countriesVitamin D - may be prevalent in racial groups moving from sunny to

temperature climates

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Minerals and trace elementsMineral/ trace element Recommended daily intake Required for

Iron 10-20mg Oxygen carriage haemoglobinCalcium 800-1200mg Calcification, cell excitabilityCobalt part of Vitamin B 12 Iodine 150 g thyroid function Copper ossification Zinc 15mg immune response

Fluorine 1ppm drinking water prevention of caries

Ion deficiency anaemia. May present with pale mucous membranes.Fairly common particularly in women (pregnancy).Calcium deficiency - rare except in vegetarians

Iodine = extremely rare as salt is iodinated

Deficiency of trace elements extremely rare as requirements are so low

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FASTINGA. 6 24 hours

Liver Glycogen glucose insulin (100g)Major source - free fatty acids from ADIPOSE TISSUE

Gluconeogenesis glucoseSmall amount of acetoacetate, B OH butyrateMajor response due to insulin

B. 2 4 days

Liver Glycogen depletedGlyconeogenesis ++ from amino acids mainly from muscle, glycerolfrom adipose tissue + lactate from Rbc

FA Ketones in liver

Hormones InsulinCortisol & adrenalineGlucagon & this peaks at 4 days.

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FASTED STATE > 2 WEEKS

1. Ketone Bodies formed as main source of energy =mainly in LIVER

2. Gluconeogenesis

3. Insulin conc. Tends to be lowCortisol be responsible foHigh levels

Adrenaline

Glucagon levels and may r reduced levels ofGluconeogenesis.

T k h

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Take home message

Energy in = energy out Avoid faulty diet balanced diet few deficienciesSpecial care in special circumstances

Less fat, more CHO

(watch the sucrose!)

Extra care in :

Less meat, more fish(EFF)

Pregnancy moreEnergy & protein plusFe, Ca, Vit D, etc etc

More exercise

Enough Fe & Ca

Fluorides (?)

Weaned infants -Protein, fatty acids, vitC etc.etc.