DIGESTIVE PHYSIOLOGY

PHYSIOLOGICAL PROCESSES

• 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

• 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

• SODIUM

• POTASSIUM

• CHLORIDE

• BICARBONATE

FUNCTIONS OF SALIVA

• LUBRICATION

• DIGESTION

• BOLUS FORMATION

• DISSOLVES FOOD SO WE CAN TASTE

• AIDS IN SPEECH

• BACTERIOSTATIC

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

FACTORS THAT ENHANCE SECRETION

• SIGHT OF FOOD

• THOUGHT OF FOOD

• ODOR OF FOOD

• PRESENCE OF IRRITATING FOODS IN STOMACH OR SMALL INTESTINE

• CHEWING

FACTORS THAT INHIBIT SECRETION

• INTENSE MENTAL EFFORT

• DEHYDRATION

• FEAR

• ANXIETY

GASTRIC SECRETIONS

• MUCUS

• HYDROCHLORIC ACID

• PEPSINOGEN

MUCUS

• 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

• MUCUS COMBINED WITH EPITHELIA

• TIGHT JUNCTIONS

• HYDROPHOBIC LAYER

• SECRETION OF PESPSINOGEN

CONTROL OF GASTRIC SECRETIONS

• CEPHALIC PHASE

• GASTRIC PHASE

• INTESTINAL PHASE

CEPHALIC PHASE

• 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

• MUCUS

• INTESTINAL JUICE

• PANCREATIC JUICE

• BILE

MUCUS

• PROTECTIVE COATING

FACTORS THAT STIMULATE SECRETION

• 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

• EXOCRINE PRODUCT

• AQUEOUS

• ISOTONIC

• HIGH BICARBONATE ION LEVEL

• PH 8.0

ENZYMES

• 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

CHENODEOXYCHLIC ACIDS

• 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

• 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 ALPHA-DEXTRIN MALTOTRIOSE AND MALTOSE

SUCROSE

• GLUCOSE

• FRUCTOSE

LACTOSE

• GLUCOSE

• GALACTOSE

ENZYMES INVOVED

• 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

• 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 SALT-MICELLES

• 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

• 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

• 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

• 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 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

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

• WATER

• UNDIGESTED FOOD RESIDUE

• MICROORGANISMS

• EPITHELIAL CELLS

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