DIGESTIVE PHYSIOLOGY

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DIGESTIVE PHYSIOLOGY
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PHYSIOLOGICAL PROCESSES

• MECHANICAL PROCESSES
• SECRETION
• CHEMICAL DIGESTION
• ABSORPTION

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MECHANICAL PROCESSES

• MOVEMENT PATTERNS

4
SEGMENTATION

• STATIONARY MUSCULAR CONTRACTIONS
• DIVIDES GI TRACT INTO CONSTRICTED OR
  UNCONSTRICTED SECTIONS

5
PERISTALSIS

• WAVE LIKE CONTRACTION
• FORCES MATERIALS TO MOVE BEFORE IT
• NORMALLY MOVES TOWARD ANUS
• PROBABLY DUE TO INTRINSIC NERVE PLEXUS

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CHEWING

• MASTICATION
• FORMS BOLUS
• REDUCES FOOD INTO SMALLER PIECES THAT ARE EASIER
  TO DIGEST

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SWALLOWING

• MOVES BOLUS FROM MOUTH TO STOMACH
• INITIATED BY TONGUE ON ROOF OF MOUTH
• PRESSURE RECEPTORS AT OPENING OF PHARYNX INITIATE
  SWALLOWING REFLEX

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SWALLOWING REFLEX

• PHARYGEAL CONSTRICTOR MUSCLES
• PERISTALTIC CONTRACTION

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UPPER ESOPHAGEAL SPHINCTER

• KEEPS ESOPHAGUS CLOSED

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EPIGLOTTIS

• WITH VOCAL CORDS KEEP FOOD FROM GOING INTO
  TRACHEA
• COUGHING REMOVES FOOD THAT DOES GET INTO TRACHEA

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MOVEMENT ALONG THE ESOPHAGUS

• PERISTALTIC CONTRACTIONS
• TUNICA MUSCULARIS

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LOWER ESOPHAGEAL SPHINCTER

• 2-5 CM ABOVE CARDIAC ORIFICE
• KEEPS OPENING TO STOMACH CLOSED
• FOOD GENERALLY TAKES ABOUT 5 -10 SECONDS TO REACH
  STOMACH

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GASTRIC MOTILITY
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MECHANICAL ACTIVITIES OF STOMACH

• STORING FOOD
• MIXING FOOD WITH GASTRIC SECRETIONS
• MOVEMENT OF FOOD INTO DUODENUM

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STOMACH VOLUME

• ABOUT 50 ML NORMALLY
• CAN EXPAND TO TO 1000-1500ML
• WILL NOT HAVE AN INCREASE IN PRESSURE
• DUE TO SMOOTH MUSCLE ABILITY TO LENGTHEN WITHOUT
  INCREASING TENSION
• ALSO DUE TO RECEPTIVE RELAXATION

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CHYME

• SEMIFLUID MIXTURE OF FOOD AND GASTRIC SECRETIONS

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PYLORIC SPHINCTER

• USUALLY PARTIALLY OPEN
• OFFERS ONLY LIMITED RESISTANCE

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STOMACH MUSCLE CONTRACTIONS

• BEGIN IN BODY
• MOVE TOWARD PYLORIC SPHINCTER
• INCREASE IN STRENGTH AND SPEED IN LOWER REGIONS
• FORCES CHYME OUT OF STOMACH INTO DUODENUM
• MATERIAL LEFT OVER REBOUNDS BACK INTO STOMACH

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PACESETTER CELLS

• SLOW WAVE POTENTIALS
• GIVES SMOOTH MUSCLE A BASIC ELECTICAL RHYTHM
• THREE CYCLES PER MINUTE CYCLES

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FACTORS THAT INFLUENCE MEMBRANE POTENTIALS

• MECHANICAL
• HORMONAL
• NEURAL

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MECHANICAL FACTORS

• VOLUME OF STOMACH
• MECHANORECEPTORS INTIATE REFLEXES TO INCREASE
  GASTRIC MOTILITY RELAXATION OF PYLORIC
  SPHINCTER PROMOTION OF GASTRIC EMPTYING
• BOTH LONG AND SHORT REFLEXES INVOLVED

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SHORT REFLEXES

• NEURAL SIGNALS ORIGINATE FROM WALL OF DIGESTIVE
  TRACT
• TRANSMITTED BY INTRINSIC NERVE PLEXUSES TO
  EFFECTOR CELLS
• ALL ELEMENTS ARE LOCATED IN DIGESTIVE TRACT WALL

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LONG REFLEXES

• AFFERENT IMPULSES TO BRAIN CENTERS
• EFFERENT IMPULSE TO INTRINSIC PLEXUSES AND
  EFFECTOR CELLS OF DIGESTIVE SYSTEM

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HORMONAL FACTORS

• GASTRIN

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EFFECT OF VOLUME AND COMPOSITION OF CHYME
ENTERING DUODENUM

• EXERTS MAJOR EFFECT ON GASTRIC MOTILITY
• EXERTS MAJOR EFFECT ON GASTRIC EMPTYING
• EXERTS BOTH HORMONAL AND NEURAL CONTROL

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ENTEROGASTRIC REFLEX

• WHEN DUODENUM FILLS WITH CHYME
• DISTENSION OF WALL
• INHIBITS GASTRIC MOTILITY
• INCREASES CONTRACTION OF PYLORIC SPHINCTER

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ENTEROGASTERONES

• COLLECTION OF HORMONES
• RELEASED IN RESPONSE TO ACID CHYME
• PRESENCE OF FAT
• PRESENCE OF CERTAIN AMINO ACIDS
• INHIBIT GASTRIC MOTILITY AND SLOW GASTRIC EMPTYING

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ENTEROGASTERONES

• SECRETIN
• MAYBE CCK AND GIP

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NET EFFECT

• TO SLOW MOVEMENT OF CHYME UNTIL SMALL INTESTINE
  HAS PROCESSED WHAT IT ALREADY HAS

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SMALL INTESTINE MOTILTY
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SEGMENTATION

• MAJOR MOVEMENT
• MOST COMMON MOVEMENT DURING MEAL
• QUITE ACTIVE JUST AFTER MEAL
• LITTLE OCCURS BETWEEN MEALS
• MIXES CHYME WITH DIGESTIVE JUICES
• INCREASES EXPOSURE TO MUCOSA

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SMOOTH MUSCLE

• HAS BASIC ELECTRICAL RHYTHM
• DETERMINES FREQUENCY OF SEGMENTATION CONTRACTIONS
• RATE VARIES THROUGHOUT SMALL INTESTINE
• GREATEST SEGMENTATION IN UPPR PART
• LEAST IN LOWER PART

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FACTORS THAT AFFECT SEGMENTATION

• MECHANICAL
• NEURAL
• HORMONAL

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MIGRATING MOTILITY COMPLEX

• SERIES OF WEAK PERISTALTIC CONTRACTIONS
• BEGINS AT DUODENUM
• NEW WAVES CONTINUE THROUGHOUT SMALL INTESTINE
• 100-150 MINUTES

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ILEOCECAL SPHINCTER

• CONTROLS MOVEMENT OF MATERIALS INTO CECUM
• MATERIAL IN CECUM INTIATES INTRINSIC NERVE PLEXUS
  TO STIMULATE SPHINCTER
• USUALLY MILDLY CONSTRICTED
• ALLOWS TIME FOR ABSORPTION

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GASTROILEAL COMPLEX

• REFLEX THAT INCREASES ILEAL CONTACTION
• OCCURS WHEN FOOD ENTERS STOMACH

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GASTRIN

• INCREASE MOTILITY IN ILEUM
• RELAXES ILEOCECAL SPHINCTER
• INCREASES MOVEMENT INTO CECUM
• ALLOWS ROOM IN STOMACH FOR MORE FOOD

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ILEOCECAL VALVE

• FOLDS OF TISSUE
• PROTECTS OPENING OF ILEUM INTO CECUM
• PREVENTS BACK FLOW

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LARGE INTESTINE MOTILITY

• SLUGGISH
• 18-24 HOURS FOR MOVEMENT THROUGH

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SEGMENTATION

• LOWER RATE THAN IN SMALL INTESTINE
• CALLED HAUSTRAL CONTACTIONS
• MAY OCCUR EVERY THIRTY MINUTES OR SO

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MASS MOVEMENTS

• OCCUR THREE OR FOUR TIMES PER DAY
• LARGE SEGMENTS OF COLON EXPERIENCE STRONG
  CONTRACTIONS
• MOVE CONTENTS FOR LONG STRETCHES
• OFTEN OCCUR AFTER MEALS

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FACTORS THAT MAY INTITIATE MASS MOVEMENTS

• DUODENUM MAY INTITIATE DUODENOCOLIC REFLEX
• STOMACH MAY INTITIATE GASTROCOLIC REFLEX
• NET EFFECT IS TO MAKE ROOM FOR MORE FOOD

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DEFECATION REFLEX

• MOVES MATERIAL OUT OF LOWER COLON AND RECTUM
• TRANSMITTED BY INTRINSIC PLEXUS
• REINFORCED BY INPUT FROM SACRAL REGION

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EFFECTS OF DEFECATION REFLEX

• SIGMOID COLON AND RECTUM CONTRACT
• INTERNAL ANAL SPHINCTER RELAXES
• FECES PROPELLED INTO ANUS
• EXTERNAL ANAL SPHINCTER DETERMINES WHETHER IT
  WILL LEAVE

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ACTIVITIES THAT ASSIST THE DEFECATION REFLEX

• DEEP INSPIRATION
• HOLDING BREATH
• CONTRACTING ABDOMINAL MUSCLES
• THESE ACTIVITIES RAISE ABDOMINAL PRESSURE

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SECRETORY ACTIVITIES OF GI TRACT
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ORAL REGION

• PAROTID GLAND
• SUBLINGUAL GLAND
• SUBMANDIBULAR GLAND
• BUCCAL GLAND

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TYPES OF SALIVA

• MUCOUS SECRETION
• SEROUS SECRETION

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PAROTID GLAND

• SEROUS SECRETIONS

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SUBMANDIBULAR GLAND

• SEROUS

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BUCCAL AND SUBLINGUAL GLANDS

• PRIMARILY MUCOUS

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MUCOUS SECRETION

• CONTAINS MUCIN MAJOR PROTEINS OF SALIVA MIX
  WITH WATER TO FORM MUCOUS
• HIGHLY VISCOUS
• LUBRICATES FOOD
• RESPONSIBLE FOR HOLDING BOLUS TOGETHER

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MUCINS

• MAJOR PROTEINS OF SALIVA
• ATTACHED TO LARGE POLYSACCHARIDES
• MIX WITH WATER TO FORM MUCUS

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IMPORTANCE OF SALIVARY AMYLASE

• SPLITS STARCH MOLECULES INTO SMALLER UNITS
• OPTIMAL PH 6.9
• RANGE 4 TO 11
• BEGINS DIGESTION OF CARBOHYDRATES
• CONTINUES IN STOMACH UNTIL ACIDS INACTIVATE

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SALIVA COMPOSITION

• VARIABLE BASED ON GLAND SECRETING AND STIMULUS
  THAT CAUSES ITS SECRETION
• 97-99.5 WATER
• PH FROM 6.--7.0
• KALLIKREIN
• BLOOD GROUP SUBSTANCES

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ELECTROLYTES IN SALIVA

• SODIUM
• POTASSIUM
• CHLORIDE
• BICARBONATE

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FUNCTIONS OF SALIVA

• LUBRICATION
• DIGESTION
• BOLUS FORMATION
• DISSOLVES FOOD SO WE CAN TASTE
• AIDS IN SPEECH
• BACTERIOSTATIC

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CONTROL OF SALIVARY SECRETIONS

• NEURAL CONTROL
• SALVATORY NUCLEI IN PONS-MEDULLA RECEIVE INPUT
  FROM MAOUTH AND PHARYNX
• AUTONOMIC NERVOUS SYSTEM CARRIES INPUT TO
  SALIVARY GLANDS

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FACTORS THAT ENHANCE SECRETION

• SIGHT OF FOOD
• THOUGHT OF FOOD
• ODOR OF FOOD
• PRESENCE OF IRRITATING FOODS IN STOMACH OR SMALL
  INTESTINE
• CHEWING

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FACTORS THAT INHIBIT SECRETION

• INTENSE MENTAL EFFORT
• DEHYDRATION
• FEAR
• ANXIETY

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GASTRIC SECRETIONS

• MUCUS
• HYDROCHLORIC ACID
• PEPSINOGEN

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MUCUS

• VISCOUS
• ALKALINE
• FORMS A LAYER 1-1.5 MM THICK
• LUBICATES WALL
• PROTECTS GASTRIC MUCOSA
• IRRITATED MUCOSA SECRETES LOTS OF MUCUS

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GLANDS THAT SECRETE MUCUS

• CARDIAC GLANDS
• PYLORIC GLANDS
• GASTRIC GLANDS IN FUNDUS AND BODY WILL ALSO
  SECRETE WITH OTHER PRODUCTS

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HYDROCHLORIC ACID

• PARIETAL CELLS OF GASTRIC GLANDS
• DISSOCIATES INTO H AND CL- IONS
• FACILITATES PROTEIN DIGESTION
• KILLS MANY BACTERIA
• SECRETORY PRODUCT AT PH OF 1.8
• ACTUAL PH OF STOMACH WILL VARY

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THEORIES OF HCL PRODUCTION

• HYDROGEN IONS ARE DISSOCIATED FROM WATER
  MOLECULES
• ACTIVELY TRANSPORTED FROM INTERIOR OF PARIETAL
  CELLS TO STOMACH LUMEN
• LEAVES BEHIND HYDROXIDE ION

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• CARBON DIOXIDE DIFFUSES INTO CELL FROM PLASMA
• WITH CARBON DIOXIDE FROM METABOLISM COMBINES WITH
  WATER TO FORM CARBONIC ACID
• CARBONIC ANHYDRASE CATALYZES

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• HYDROGEN AND HYDROXIDE IONS JOIN TO FORM WATER
• ACTIVE TRANSPORT REMOVES BICARONATE IONS INTO
  PLASMA IN EXCHANGE FOR CHLORIDE IONS
• CHLORIDE IONS LEAVE CELL AND ENTER LUMEN OF
  STOMACH

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EFFECT ON PLASMA pH

• BICARBONATE CAUSES PH OF VENOUS BLOOD FROM
  STOMACH TO BE HIGHER THAN BLOOD FLOWING TO THE
  STOMACH

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PEPSINOGEN

• ZYMOGENIC OR CHIEF CELLS
• PRECURSOR TO PEPSIN
• ACIDIC ENVIRONMENT CAUSES CONVERSION
• PEPSIN CAN ALSO CONVERT OTHER PEPSINOGENS

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PEPSIN

• WORKS BEST IN ACID ENVIRONMENT
• DIGEST PROTEINS BY BREAKING PEPTIDE BONDS
  INVOLVING TRYTOPHAN, PHENYLALANINE, AND
  TYROSINE
• PRODUCES SMALLER PEPTIDE CHAINS

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MUCUS PRODUCTION AND THE PROTECTION OF THE STOMACH

• MUCUS COMBINED WITH EPITHELIA
• TIGHT JUNCTIONS
• HYDROPHOBIC LAYER
• SECRETION OF PESPSINOGEN

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CONTROL OF GASTRIC SECRETIONS

• CEPHALIC PHASE
• GASTRIC PHASE
• INTESTINAL PHASE

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CEPHALIC PHASE

• SIGHT
• SMELL
• TASTE
• DUE TO SENSORY INPUT TO CNS
• VAGUS CARRIES INPUT FROM CNS TO STOMACH
• CONDITIONED REFLEX

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GASTRIC PHASE

• SIGNALS ORIGINATE IN STOMACH
• DISTENSION OF STOMACH
• INCREASES AMOUNT OF PEPSIN AND ACIDITY

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CONTROL OF GASTRIC PHASE

• SHORT REFLEXES
• LONG REFLEXES

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FACTORS THAT CAUSE THE PRODUCTION OF GASTRIN

• DISTENSION OF PYLORIC REGION CAUSES LOCAL
  REFLEXES
• SECRETAGOGUES CAFFEINE PARTIALLY DIGESTED
  PROTEIN

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FACTORS THAT INHIBIT GASTRIN RELEASE

• HIGH CONCENTRATIONS OF HYDROGEN IONS IN STOMACH
• PH OF TWO BLOCKS GASTRIN PRODUCTION

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INTESTINAL PHASE

• CAUSED BY SIGNALS FROM SMALL INTESTINE
• WEAK EXCITATORY COMPONENT
• STRONGER INHIBITORY COMPONENT

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EXCITATORY COMPONENT

• CAN BE SEEN WHEN CHYME ENTERS DUODENUM
• PROBABLY DUE TO INTESTINAL GASTRIN FROM DUODENAL
  MUCOSA
• OTHER HORMONES ARE INVOLVED

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INHIBITORY COMPONENT

• NEURAL
• HORMONAL

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FACTORS INVOLVED

• DISTENSION OF DUODENUM
• EXCESSIVE ACIDITY OF CHYME
• HYPER OR HYPOTONICITY OF CHYME
• INTITIATES ENTEROGASTRIC REFLEX
• SHORT AND LONG REFLEXES

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ENTEROGASTERONES

• ACIDITY OF CHYME
• PRESENCE OF SOME FATS OR AMINO ACIDS
• ARE INHIBITORY

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SECRETIONS FOUND IN THE SMALL INTESTINE

• MUCUS
• INTESTINAL JUICE
• PANCREATIC JUICE
• BILE

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MUCUS

• PROTECTIVE COATING

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FACTORS THAT STIMULATE SECRETION

• TACTILE STIMULATION OF MUCOSA
• IRRITATION OF MUCOSA
• VAGAL STIMULATION
• SECRETIN AND OTHER INTESTINAL HORMONES

86
SITES OF SECRETION

• GOLBET CELLS
• DUODENAL CELLS
• INTESTINAL GLANDS

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CONTROL OF SECRETION

• MOST LIKELY DUE TO LOCAL NERVE REFLEXES

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INTESTINAL JUICE

• LOCATED THROUGHOUT SMALL INTESTINE
• PH OF 6.5 TO 7.5
• ISOTONIC TO PLASMA

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FACTORS THAT AFFECT SECRETION

• LOCAL REFLEXES INTIATED BY INTESTINAL MUCOSA
• SECRETIN
• CCK

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SECRETION

• PRODUCED BY EPITHELIAL CELLS
• ENZYMES ARE ASSOCIATED WITH CELL MEMBRANES NOT IN
  LUMEN
• INCLUDES DISSACHRIDASES AND PEPTIDASES

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PANCREATIC JUICE

• EXOCRINE PRODUCT
• AQUEOUS
• ISOTONIC
• HIGH BICARBONATE ION LEVEL
• PH 8.0

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ENZYMES

• VARIOUS CARBOHYDRATE ENZYME
• PROTEASES
• LIPIDASES
• RIBONUCLEASES
• DOXYRIBONUCLEASES

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CONTROL OF SECRETION

• HORMONAL
• NEURAL

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HORMONAL

• SECRETIN
• CCK

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SECRETIN

• RELEASED IN RESPONSE TO ACID IN DUODENUM
• RELEASE OF WATERY BICARBONATE SOLUTIONS

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CCK

• PRESENCE OF CERTAIN AMINO ACIDS AND FATTY ACIDS
  IN DUODENUM
• RELEASE OF DIGESTIVE ENZYMES

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NEURAL

• VAGUS
• EFFECTS MAINLY ENZYMATIC SECRETION
• OCCURS MAINLY IN CEPHALIC AND GASTRIC PHASES

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BILE

• PRODUCED BY LIVER
• 600-1000 ml PER DAY
• TRAVELS TO SMALL INTESTINE BY DUCTS
• CAN BE STORED IN GALL BLADDER

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COMPONENTS OF BILE

• AQUEOUS SOLUTION
• SODIUM
• BICARBONATES
• CHOLIC AND CHENODEOXYCHLIC ACIDS

• BILIRUBIN
• CHOLESTEROL
• NEUTRAL FATS
• LECITHIN

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FATE OF BILE

• 94 REABOSRBED IN ILEUM
• RETURNED TO LIVER BY ENTEROHEPATIC CIRCULATION

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CONTOL OF BILE SECRETION

• CHEMICAL
• HORMONAL
• NEURAL

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CHEMICAL

• BILE SALTS IN PLASMA CAUSE SECRETION OF MORE BILE
  SALTS

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HORMONAL

• SECRETIN

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NEURAL

• PARASYMPATHETIC INNERVATION BY VAGUS

105
BILE STORAGE

• GALLBLADDER
• CAN STORE 40 TO 70 ML
• REABSORBS WATER AND ELECTROLYTES
• CONCENTRATION OF BILE SALTS AND PIGMENTS CAN
  INCREASE 5TO TEN TIMES

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ROLE OF GALLBLADDER IN DIGESTION

• GALLBLADDER CONTRACTION RELEASES BILE INTO
  DUODENUM
• PRIMARILY CAUSED BY CCK
• PARASYMPATHETIC INNERVATION CAN CAUSE WEAK
  CONTRACTIONS

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SECRETIONS OF THE LARGE INTESTINE

• MUCUS
• MUCUS
• AND MORE MUCUS

108
CONTROL OF MUCUS SECRETIONS

• DIRECT TACTILE STIMLATION
• INTRINSIC REFLEXIS
• EXTRINSIC REFLEXES

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DIGESTIVE PROCESSES
110
DIGESTION

• BREAKDOWN LARGE MOLECULES INTO SMALLER ONES
• WORK BY HYDROLYSIS
• SMALL INTESTINE DOES MOST

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ABSORPTION

• PRODUCTS OF DIGESTION
• VITAMINS
• MINERALS
• WATER
• SMALL INTESTINE DOES MOST

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DIGESTION OF COMMON NUTRIENTS
113
CARBOHYDRATES

• STARCH
• SUCROSE
• LACTOSE

114
STARCHES

• AMYLASES IN SALIVA
• AMYLASES IN PANCREATIC JUICE
• STARCH IS BROKEN INTO ALPHA-DEXTRIN MALTOTRIOSE
  AND MALTOSE

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SUCROSE

• GLUCOSE
• FRUCTOSE

116
LACTOSE

• GLUCOSE
• GALACTOSE

117
ENZYMES INVOVED

• LOCATED ON MICROVILLI
• ALPHA DEXTINASE
• MALTASE
• SUCRASE
• LACTASE

118
ABSORPTION OF SUGARS

• PRIMARILY IN DUODENUM AND UPPER JEJUNUM
• GLUCOSE AND GALACTOSE--ACTIVE TRANSPORT
• FRUCTOSE--FACILITATED DIFFUSION

119
PROTEINS
120
ENZYMES THAT DIGEST PROTEINS

• TRYPSIN
• CHYMOTRYPSIN
• CARBOXYPEPTIDASE

121
TRYPSIN

• BREAKS BONDS BETWEEN LYSINE AND ARGININE

122
CHYMOTRYPSIN

• BREAKS BONDS BETWEEN TYROSINE AND PHENYLALANINE

123
CARBOXYPEPTIDASE

• REMOVES CARBOXYL GROUP FROM END OF AMINO ACID

124
ENZYMES OF MICROVILLI

• CONTINUE PROCESS
• AMINOPEPTIDASES
• TETRAPEPTIDASES
• TRIPEPTIDASES

125
SITES OF PROTEIN DIGESTION

• BEGINS IN STOMACH
• MOST OCCURS IN SMALL INTESTINE
• SIXTY TO EIGHTY PERCENT DIGESTED BY TIME IT
  REACHES ILEUM

126
ABSORPTION

• ACTIVE TRANSPORT OF AMINO ACIDS, DIPEPTIDES, AND
  TRIPEPTIDES
• DIPEPTIDASES AND TRIPEPTIDASES BREAK DOWN
• AMINO ACIDS ENTER BLOOD STREAM

127
LIPIDS

• MAINLY TRIGLYCERIDES
• DIGESTION PRIMARILY IN SMALL INTESTINE
• EMULSIFICATION
• BILE SALTS ESSENTIAL
• FORMS MONOGYLCERIDES AND FREE FATTY ACIDS

128
BILE SALTS

• AMPHIPATHIC
• FORM MICELLES
• MONOGLYCERIDES AND FREE FATTY ACIDS BINDWITH BILE
  SALT-MICELLES
• TAKEN TO INTESTINAL EPITHELIUM

129
ABSORPTION

• MONOGLYCERIDES AND FREE FATTY ACIDS DISSOCIATE
• ENTER EPITHELIAL CELLS BY SIMPLE DIFFUSION
• BILE SALTS ARE REUSED
• EVENTUALLY REABSORBED IN ILEUM

130
INTESTINAL EPITHELIAL CELLS

• MUCH OF THE MONOGLYCERIDES ARE BROKEN DOWN INTO
  GLYCEROL AND FATTY ACID
• EPITHELIAL LIPASE IS THE ENZYME
• IN ENDOPLASMIC RETICULM FREE FATTY ACIDS ARE
  AGAIN COMBINED WITH GLYCEROL
• NEW GLYCEROL AND OLD GLYCEROL

131
OTHER PRODUCTS

• PHOSPHOLIPIDS
• CHOLESTEROL
• PROTEINS

132
FATE OF PRODUCTS

• PRODUCTS ARE PACKAGED IN MEMBRANE BOUND VESICLES
• CONTAIN TRIGLYCERIDES, PHOSPHOLIPIDS, CHOLESTEROL
  AND SOME FREE FATTY ACIDS
• EXOCYTOSIS
• ENTER LACTEALS

133
CHYLOMICRONS

• ABOUT 90 TRIGLYCERIDES
• 5 PHOSPHOLIPIDS
• 4 FREE FATTY ACIDS
• 1 CHOLESTEROL
• SOME PROTEIN

134
SITE OF ABSORPTION

• DUODENUM
• JEJUNUM
• COMPLETED BY TIME REACHES ILEUM

135
FATE OF INGESTED CHOLESTEROL

• FREE CHOLESTEROL
• CHOLESTEROL ESTERS
• PANCREATIC CHOLESTEROL ESTERASE
• FREE CHOLESTEROL ASSOCIATES WITH MICELLES AND IS
  ABSORBED

136
VITAMIN ABSORPTION

• FAT SOLUBLE
• WATER SOLUBLE

137
FAT SOLUBLE VITAMINS

• A
• D
• E
• K
• ASSOCIATE WITH MICELLES
• FAT REQUIRED FOR ABSORPTION

138
WATER SOLUBLE

• C
• B (EXCEPT B12)
• ABSORBED BY PASSIVE TRANSPORT

139
VITAMIN B12 ABSORPTION

• INTRINSIC FACTOR NECESSARY
• PRODUCED BY STOMACH
• ACTIVELY TRANSPORTED IN ILEUM

140
MINERAL ABSORPTION

• ACTIVE PROCESSES
• PASSIVE PROCESSES

141
ACTIVE TRANSPORT OF MINERALS

• SODIUM
• POTASSIUM
• MAGNESIUM
• PHOSPHATE
• CHLORINE IN THE ILEUM--COUPLED TO BICARBONATE IONS

142
PASSIVE TRANSPORT

• CHLORIDE IN UPPER PART OF SMALL INTESTINE

143
CALCIUM

• ACTIVELY ALONG THE ENTIRE SMALL INTESTINE
• ESPECIALLY IN DUODENUM
• REQUIRES VITAMIN D

144
WATER

• SMALL INTESTINE CAN ABSORB 200-400 ML OF WATER
  PER HOUR
• 0.5 L OF WATER ENTERS COLON
• SMALL INTESTINE ABSORBS ALMOST ALL THE WATER
• MOVES ACCORDING TO OSMOTIC GRADIENT

145
ABSORPTION IN LARGE INTESTINE

• SODIUM ACTIVELY ABSORBED
• CHLORIDE FOLLOWS PASSIVELY

146
SECRETION IN LARGE INTESTINE

• BICARBONATE IONS SECRETED

147
WATER ABSORPTION

• 300 - 400 ML WATER PER DAY
• DUE TO SODIUM AND CHLORIDE TRANSPORT

148
BACTERIA IN LARGE INTESTINE

• GIANT FERMENTATION VESSEL
• SYNTHESIZED IMPORTANT VITAMINS
• USUALLY ONLY A SMALL AMOUNT OF OUR DIET

149
FECAL MATERIAL

• WATER
• UNDIGESTED FOOD RESIDUE
• MICROORGANISMS
• EPITHELIAL CELLS

150
EFFECT OF AGING ON THE DIGESTIVE SYSTEM

• DIMINISHED SECRETIONS
• MUSCLES WEAKEN
• ATROPHY OF SALIVARY GLANDS
• TOOTH LOSS
• LOSS OF SENSATION OF TASTE
• SWALLOWING DIFFICULTIES
• DIVERTICULA