DIGESTIVE PHYSIOLOGY
PHYSIOLOGICAL
PROCESSES
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MECHANICAL PROCESSES
SECRETION
CHEMICAL DIGESTION
ABSORPTION
MECHANICAL PROCESSES
MOVEMENT PATTERNS
SEGMENTATION
• STATIONARY MUSCULAR
CONTRACTIONS
• DIVIDES GI TRACT INTO
CONSTRICTED OR UNCONSTRICTED
SECTIONS
PERISTALSIS
• WAVE LIKE CONTRACTION
• FORCES MATERIALS TO MOVE
BEFORE IT
• NORMALLY MOVES TOWARD ANUS
• PROBABLY DUE TO INTRINSIC NERVE
PLEXUS
CHEWING
• MASTICATION
• FORMS BOLUS
• REDUCES FOOD INTO SMALLER
PIECES THAT ARE EASIER TO DIGEST
SWALLOWING
• MOVES BOLUS FROM MOUTH TO
STOMACH
• INITIATED BY TONGUE ON ROOF OF
MOUTH
• PRESSURE RECEPTORS AT OPENING
OF PHARYNX INITIATE SWALLOWING
REFLEX
SWALLOWING REFLEX
• PHARYGEAL CONSTRICTOR
MUSCLES
• PERISTALTIC CONTRACTION
UPPER ESOPHAGEAL
SPHINCTER
• KEEPS ESOPHAGUS CLOSED
EPIGLOTTIS
• WITH VOCAL CORDS KEEP FOOD
FROM GOING INTO TRACHEA
• COUGHING REMOVES FOOD THAT
DOES GET INTO TRACHEA
MOVEMENT ALONG THE
ESOPHAGUS
• PERISTALTIC CONTRACTIONS
• TUNICA MUSCULARIS
LOWER ESOPHAGEAL
SPHINCTER
• 2-5 CM ABOVE CARDIAC ORIFICE
• KEEPS OPENING TO STOMACH
CLOSED
• FOOD GENERALLY TAKES ABOUT 5 10 SECONDS TO REACH STOMACH
GASTRIC MOTILITY
MECHANICAL ACTIVITIES
OF STOMACH
• STORING FOOD
• MIXING FOOD WITH GASTRIC
SECRETIONS
• MOVEMENT OF FOOD INTO
DUODENUM
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
CHYME
• SEMIFLUID MIXTURE OF FOOD AND
GASTRIC SECRETIONS
PYLORIC SPHINCTER
• USUALLY PARTIALLY OPEN
• OFFERS ONLY LIMITED RESISTANCE
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
PACESETTER CELLS
• SLOW WAVE POTENTIALS
• GIVES SMOOTH MUSCLE A BASIC
ELECTICAL RHYTHM
• THREE CYCLES PER MINUTE CYCLES
FACTORS THAT INFLUENCE
MEMBRANE POTENTIALS
• MECHANICAL
• HORMONAL
• NEURAL
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
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
LONG REFLEXES
• AFFERENT IMPULSES TO BRAIN
CENTERS
• EFFERENT IMPULSE TO INTRINSIC
PLEXUSES AND EFFECTOR CELLS OF
DIGESTIVE SYSTEM
HORMONAL FACTORS
• GASTRIN
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
ENTEROGASTRIC REFLEX
• WHEN DUODENUM FILLS WITH
CHYME
• DISTENSION OF WALL
• INHIBITS GASTRIC MOTILITY
• INCREASES CONTRACTION OF
PYLORIC SPHINCTER
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
ENTEROGASTERONES
• SECRETIN
• MAYBE CCK AND GIP
NET EFFECT
• TO SLOW MOVEMENT OF CHYME
UNTIL SMALL INTESTINE HAS
PROCESSED WHAT IT ALREADY HAS
SMALL INTESTINE MOTILTY
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
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
FACTORS THAT AFFECT
SEGMENTATION
• MECHANICAL
• NEURAL
• HORMONAL
MIGRATING MOTILITY
COMPLEX
• SERIES OF WEAK PERISTALTIC
CONTRACTIONS
• BEGINS AT DUODENUM
• NEW WAVES CONTINUE
THROUGHOUT SMALL INTESTINE
• 100-150 MINUTES
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
GASTROILEAL COMPLEX
• REFLEX THAT INCREASES ILEAL
CONTACTION
• OCCURS WHEN FOOD ENTERS
STOMACH
GASTRIN
• INCREASE MOTILITY IN ILEUM
• RELAXES ILEOCECAL SPHINCTER
• INCREASES MOVEMENT INTO
CECUM
• ALLOWS ROOM IN STOMACH FOR
MORE FOOD
ILEOCECAL VALVE
• FOLDS OF TISSUE
• PROTECTS OPENING OF ILEUM INTO
CECUM
• PREVENTS BACK FLOW
LARGE INTESTINE
MOTILITY
• SLUGGISH
• 18-24 HOURS FOR MOVEMENT
THROUGH
SEGMENTATION
• LOWER RATE THAN IN SMALL
INTESTINE
• CALLED HAUSTRAL CONTACTIONS
• MAY OCCUR EVERY THIRTY
MINUTES OR SO
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
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
DEFECATION REFLEX
• MOVES MATERIAL OUT OF LOWER
COLON AND RECTUM
• TRANSMITTED BY INTRINSIC
PLEXUS
• REINFORCED BY INPUT FROM
SACRAL REGION
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
ACTIVITIES THAT ASSIST
THE DEFECATION REFLEX
• DEEP INSPIRATION
• HOLDING BREATH
• CONTRACTING ABDOMINAL
MUSCLES
• THESE ACTIVITIES RAISE
ABDOMINAL PRESSURE
SECRETORY ACTIVITIES OF
GI TRACT
ORAL REGION
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PAROTID GLAND
SUBLINGUAL GLAND
SUBMANDIBULAR GLAND
BUCCAL GLAND
TYPES OF SALIVA
• MUCOUS SECRETION
• SEROUS SECRETION
PAROTID GLAND
• SEROUS SECRETIONS
SUBMANDIBULAR GLAND
• SEROUS
BUCCAL AND SUBLINGUAL
GLANDS
• PRIMARILY MUCOUS
MUCOUS SECRETION
• CONTAINS MUCIN
MAJOR PROTEINS OF SALIVA
MIX WITH WATER TO FORM
MUCOUS
• HIGHLY VISCOUS
• LUBRICATES FOOD
• RESPONSIBLE FOR HOLDING BOLUS
TOGETHER
MUCINS
• MAJOR PROTEINS OF SALIVA
• ATTACHED TO LARGE
POLYSACCHARIDES
• MIX WITH WATER TO FORM MUCUS
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
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
ELECTROLYTES IN SALIVA
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SODIUM
POTASSIUM
CHLORIDE
BICARBONATE
FUNCTIONS OF SALIVA
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LUBRICATION
DIGESTION
BOLUS FORMATION
DISSOLVES FOOD SO WE CAN TASTE
AIDS IN SPEECH
BACTERIOSTATIC
CONTROL OF SALIVARY
SECRETIONS
• NEURAL CONTROL
• SALVATORY NUCLEI IN PONSMEDULLA RECEIVE INPUT FROM
MAOUTH AND PHARYNX
• AUTONOMIC NERVOUS SYSTEM
CARRIES INPUT TO SALIVARY
GLANDS
FACTORS THAT ENHANCE
SECRETION
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SIGHT OF FOOD
THOUGHT OF FOOD
ODOR OF FOOD
PRESENCE OF IRRITATING FOODS IN
STOMACH OR SMALL INTESTINE
• CHEWING
FACTORS THAT INHIBIT
SECRETION
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INTENSE MENTAL EFFORT
DEHYDRATION
FEAR
ANXIETY
GASTRIC SECRETIONS
• MUCUS
• HYDROCHLORIC ACID
• PEPSINOGEN
MUCUS
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VISCOUS
ALKALINE
FORMS A LAYER 1-1.5 MM THICK
LUBICATES WALL
PROTECTS GASTRIC MUCOSA
IRRITATED MUCOSA SECRETES LOTS
OF MUCUS
GLANDS THAT SECRETE
MUCUS
• CARDIAC GLANDS
• PYLORIC GLANDS
• GASTRIC GLANDS IN FUNDUS AND
BODY WILL ALSO SECRETE WITH
OTHER PRODUCTS
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
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
• CARBON DIOXIDE DIFFUSES INTO
CELL FROM PLASMA
• WITH CARBON DIOXIDE FROM
METABOLISM COMBINES WITH
WATER TO FORM CARBONIC ACID
• CARBONIC ANHYDRASE CATALYZES
• 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
EFFECT ON PLASMA pH
• BICARBONATE CAUSES PH OF
VENOUS BLOOD FROM STOMACH TO
BE HIGHER THAN BLOOD FLOWING
TO THE STOMACH
PEPSINOGEN
• ZYMOGENIC OR CHIEF CELLS
• PRECURSOR TO PEPSIN
• ACIDIC ENVIRONMENT CAUSES
CONVERSION
• PEPSIN CAN ALSO CONVERT OTHER
PEPSINOGENS
PEPSIN
• WORKS BEST IN ACID ENVIRONMENT
• DIGEST PROTEINS BY BREAKING
PEPTIDE BONDS INVOLVING:
TRYTOPHAN, PHENYLALANINE, AND
TYROSINE
• PRODUCES SMALLER PEPTIDE
CHAINS
MUCUS PRODUCTION AND
THE PROTECTION OF THE
STOMACH
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MUCUS COMBINED WITH EPITHELIA
TIGHT JUNCTIONS
HYDROPHOBIC LAYER
SECRETION OF PESPSINOGEN
CONTROL OF GASTRIC
SECRETIONS
• CEPHALIC PHASE
• GASTRIC PHASE
• INTESTINAL PHASE
CEPHALIC PHASE
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SIGHT
SMELL
TASTE
DUE TO SENSORY INPUT TO CNS
VAGUS CARRIES INPUT FROM CNS TO
STOMACH
• CONDITIONED REFLEX
GASTRIC PHASE
• SIGNALS ORIGINATE IN STOMACH
• DISTENSION OF STOMACH
• INCREASES AMOUNT OF PEPSIN AND
ACIDITY
CONTROL OF GASTRIC
PHASE
• SHORT REFLEXES
• LONG REFLEXES
FACTORS THAT CAUSE THE
PRODUCTION OF GASTRIN
• DISTENSION OF PYLORIC REGION
CAUSES LOCAL REFLEXES
• SECRETAGOGUES
CAFFEINE
PARTIALLY DIGESTED PROTEIN
FACTORS THAT INHIBIT
GASTRIN RELEASE
• HIGH CONCENTRATIONS OF
HYDROGEN IONS IN STOMACH
• PH OF TWO BLOCKS GASTRIN
PRODUCTION
INTESTINAL PHASE
• CAUSED BY SIGNALS FROM SMALL
INTESTINE
• WEAK EXCITATORY COMPONENT
• STRONGER INHIBITORY COMPONENT
EXCITATORY COMPONENT
• CAN BE SEEN WHEN CHYME ENTERS
DUODENUM
• PROBABLY DUE TO INTESTINAL
GASTRIN FROM DUODENAL MUCOSA
• OTHER HORMONES ARE INVOLVED
INHIBITORY COMPONENT
• NEURAL
• HORMONAL
FACTORS INVOLVED
• DISTENSION OF DUODENUM
• EXCESSIVE ACIDITY OF CHYME
• HYPER OR HYPOTONICITY OF
CHYME
• INTITIATES ENTEROGASTRIC REFLEX
• SHORT AND LONG REFLEXES
ENTEROGASTERONES
• ACIDITY OF CHYME
• PRESENCE OF SOME FATS OR AMINO
ACIDS
• ARE INHIBITORY
SECRETIONS FOUND IN THE
SMALL INTESTINE
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MUCUS
INTESTINAL JUICE
PANCREATIC JUICE
BILE
MUCUS
• PROTECTIVE COATING
FACTORS THAT STIMULATE
SECRETION
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TACTILE STIMULATION OF MUCOSA
IRRITATION OF MUCOSA
VAGAL STIMULATION
SECRETIN AND OTHER INTESTINAL
HORMONES
SITES OF SECRETION
• GOLBET CELLS
• DUODENAL CELLS
• INTESTINAL GLANDS
CONTROL OF SECRETION
• MOST LIKELY DUE TO LOCAL NERVE
REFLEXES
INTESTINAL JUICE
• LOCATED THROUGHOUT SMALL
INTESTINE
• PH OF 6.5 TO 7.5
• ISOTONIC TO PLASMA
FACTORS THAT AFFECT
SECRETION
• LOCAL REFLEXES INTIATED BY
INTESTINAL MUCOSA
• SECRETIN
• CCK
SECRETION
• PRODUCED BY EPITHELIAL CELLS
• ENZYMES ARE ASSOCIATED WITH
CELL MEMBRANES NOT IN LUMEN
• INCLUDES: DISSACHRIDASES AND
PEPTIDASES
PANCREATIC JUICE
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EXOCRINE PRODUCT
AQUEOUS
ISOTONIC
HIGH BICARBONATE ION LEVEL
PH 8.0
ENZYMES
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VARIOUS CARBOHYDRATE ENZYME
PROTEASES
LIPIDASES
RIBONUCLEASES
DOXYRIBONUCLEASES
CONTROL OF SECRETION
• HORMONAL
• NEURAL
HORMONAL
• SECRETIN
• CCK
SECRETIN
• RELEASED IN RESPONSE TO ACID IN
DUODENUM
• RELEASE OF WATERY BICARBONATE
SOLUTIONS
CCK
• PRESENCE OF CERTAIN AMINO ACIDS
AND FATTY ACIDS IN DUODENUM
• RELEASE OF DIGESTIVE ENZYMES
NEURAL
• VAGUS
• EFFECTS MAINLY ENZYMATIC
SECRETION
• OCCURS MAINLY IN CEPHALIC AND
GASTRIC PHASES
BILE
• PRODUCED BY LIVER
• 600-1000 ml PER DAY
• TRAVELS TO SMALL INTESTINE BY
DUCTS
• CAN BE STORED IN GALL BLADDER
COMPONENTS OF BILE
• AQUEOUS
SOLUTION
• SODIUM
• BICARBONATES
• CHOLIC AND
CHENODEOXYCHL
IC ACIDS
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BILIRUBIN
CHOLESTEROL
NEUTRAL FATS
LECITHIN
FATE OF BILE
• 94% REABOSRBED IN ILEUM
• RETURNED TO LIVER BY
ENTEROHEPATIC CIRCULATION
CONTOL OF BILE
SECRETION
• CHEMICAL
• HORMONAL
• NEURAL
CHEMICAL
• BILE SALTS IN PLASMA CAUSE
SECRETION OF MORE BILE SALTS
HORMONAL
• SECRETIN
NEURAL
• PARASYMPATHETIC INNERVATION BY
VAGUS
BILE STORAGE
• GALLBLADDER
• CAN STORE 40 TO 70 ML
• REABSORBS WATER AND
ELECTROLYTES
• CONCENTRATION OF BILE SALTS
AND PIGMENTS CAN INCREASE 5TO
TEN TIMES
ROLE OF GALLBLADDER IN
DIGESTION
• GALLBLADDER CONTRACTION
RELEASES BILE INTO DUODENUM
• PRIMARILY CAUSED BY CCK
• PARASYMPATHETIC INNERVATION
CAN CAUSE WEAK CONTRACTIONS
SECRETIONS OF THE LARGE
INTESTINE
• MUCUS
• MUCUS
• AND MORE MUCUS
CONTROL OF MUCUS
SECRETIONS
• DIRECT TACTILE STIMLATION
• INTRINSIC REFLEXIS
• EXTRINSIC REFLEXES
DIGESTIVE PROCESSES
DIGESTION
• BREAKDOWN LARGE MOLECULES
INTO SMALLER ONES
• WORK BY HYDROLYSIS
• SMALL INTESTINE DOES MOST
ABSORPTION
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PRODUCTS OF DIGESTION
VITAMINS
MINERALS
WATER
SMALL INTESTINE DOES MOST
DIGESTION OF COMMON
NUTRIENTS
CARBOHYDRATES
• STARCH
• SUCROSE
• LACTOSE
STARCHES
• AMYLASES IN SALIVA
• AMYLASES IN PANCREATIC JUICE
• STARCH IS BROKEN INTO ALPHADEXTRIN MALTOTRIOSE AND
MALTOSE
SUCROSE
• GLUCOSE
• FRUCTOSE
LACTOSE
• GLUCOSE
• GALACTOSE
ENZYMES INVOVED
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LOCATED ON MICROVILLI
ALPHA DEXTINASE
MALTASE
SUCRASE
LACTASE
ABSORPTION OF SUGARS
• PRIMARILY IN DUODENUM AND
UPPER JEJUNUM
• GLUCOSE AND GALACTOSE--ACTIVE
TRANSPORT
• FRUCTOSE--FACILITATED DIFFUSION
PROTEINS
ENZYMES THAT DIGEST
PROTEINS
• TRYPSIN
• CHYMOTRYPSIN
• CARBOXYPEPTIDASE
TRYPSIN
• BREAKS BONDS BETWEEN LYSINE
AND ARGININE
CHYMOTRYPSIN
• BREAKS BONDS BETWEEN TYROSINE
AND PHENYLALANINE
CARBOXYPEPTIDASE
• REMOVES CARBOXYL GROUP FROM
END OF AMINO ACID
ENZYMES OF MICROVILLI
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CONTINUE PROCESS
AMINOPEPTIDASES
TETRAPEPTIDASES
TRIPEPTIDASES
SITES OF PROTEIN
DIGESTION
• BEGINS IN STOMACH
• MOST OCCURS IN SMALL INTESTINE
• SIXTY TO EIGHTY PERCENT
DIGESTED BY TIME IT REACHES
ILEUM
ABSORPTION
• ACTIVE TRANSPORT OF AMINO
ACIDS, DIPEPTIDES, AND
TRIPEPTIDES
• DIPEPTIDASES AND TRIPEPTIDASES
BREAK DOWN
• AMINO ACIDS ENTER BLOOD
STREAM
LIPIDS
• MAINLY TRIGLYCERIDES
• DIGESTION PRIMARILY IN SMALL
INTESTINE
• EMULSIFICATION
• BILE SALTS ESSENTIAL
• FORMS MONOGYLCERIDES AND
FREE FATTY ACIDS
BILE SALTS
• AMPHIPATHIC
• FORM MICELLES
• MONOGLYCERIDES AND FREE FATTY
ACIDS BINDWITH BILE SALTMICELLES
• TAKEN TO INTESTINAL EPITHELIUM
ABSORPTION
• MONOGLYCERIDES AND FREE FATTY
ACIDS DISSOCIATE
• ENTER EPITHELIAL CELLS BY
SIMPLE DIFFUSION
• BILE SALTS ARE REUSED
• EVENTUALLY REABSORBED IN
ILEUM
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
OTHER PRODUCTS
• PHOSPHOLIPIDS
• CHOLESTEROL
• PROTEINS
FATE OF PRODUCTS
• PRODUCTS ARE PACKAGED IN
MEMBRANE BOUND VESICLES
• CONTAIN TRIGLYCERIDES,
PHOSPHOLIPIDS, CHOLESTEROL AND
SOME FREE FATTY ACIDS
• EXOCYTOSIS
• ENTER LACTEALS
CHYLOMICRONS
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ABOUT 90% TRIGLYCERIDES
5% PHOSPHOLIPIDS
4% FREE FATTY ACIDS
1% CHOLESTEROL
SOME PROTEIN
SITE OF ABSORPTION
• DUODENUM
• JEJUNUM
• COMPLETED BY TIME REACHES
ILEUM
FATE OF INGESTED
CHOLESTEROL
• FREE CHOLESTEROL
• CHOLESTEROL ESTERS
• PANCREATIC CHOLESTEROL
ESTERASE
• FREE CHOLESTEROL ASSOCIATES
WITH MICELLES AND IS ABSORBED
VITAMIN ABSORPTION
• FAT SOLUBLE
• WATER SOLUBLE
FAT SOLUBLE VITAMINS
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A
D
E
K
ASSOCIATE WITH MICELLES
FAT REQUIRED FOR ABSORPTION
WATER SOLUBLE
• C
• B (EXCEPT B12)
• ABSORBED BY PASSIVE TRANSPORT
VITAMIN B12 ABSORPTION
• INTRINSIC FACTOR NECESSARY
• PRODUCED BY STOMACH
• ACTIVELY TRANSPORTED IN ILEUM
MINERAL ABSORPTION
• ACTIVE PROCESSES
• PASSIVE PROCESSES
ACTIVE TRANSPORT OF
MINERALS
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SODIUM
POTASSIUM
MAGNESIUM
PHOSPHATE
CHLORINE IN THE ILEUM--COUPLED
TO BICARBONATE IONS
PASSIVE TRANSPORT
• CHLORIDE IN UPPER PART OF SMALL
INTESTINE
CALCIUM
• ACTIVELY ALONG THE ENTIRE
SMALL INTESTINE
• ESPECIALLY IN DUODENUM
• REQUIRES VITAMIN D
WATER
• SMALL INTESTINE CAN ABSORB 200400 ML OF WATER PER HOUR
• 0.5 L OF WATER ENTERS COLON
• SMALL INTESTINE ABSORBS ALMOST
ALL THE WATER
• MOVES ACCORDING TO OSMOTIC
GRADIENT
ABSORPTION IN LARGE
INTESTINE
• SODIUM ACTIVELY ABSORBED
• CHLORIDE FOLLOWS PASSIVELY
SECRETION IN LARGE
INTESTINE
• BICARBONATE IONS SECRETED
WATER ABSORPTION
• 300 - 400 ML WATER PER DAY
• DUE TO SODIUM AND CHLORIDE
TRANSPORT
BACTERIA IN LARGE
INTESTINE
• GIANT FERMENTATION VESSEL
• SYNTHESIZED IMPORTANT VITAMINS
• USUALLY ONLY A SMALL AMOUNT
OF OUR DIET
FECAL MATERIAL
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WATER
UNDIGESTED FOOD RESIDUE
MICROORGANISMS
EPITHELIAL CELLS
EFFECT OF AGING ON THE
DIGESTIVE SYSTEM
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DIMINISHED SECRETIONS
MUSCLES WEAKEN
ATROPHY OF SALIVARY GLANDS
TOOTH LOSS
LOSS OF SENSATION OF TASTE
SWALLOWING DIFFICULTIES
DIVERTICULA