THE DIGESTIVE SYSTEM II
D. C. Mikulecky
Faculty Mentoring Program
Virginia Commonwealth University
PANCREATIC AND BILLIARY
SECRETIONS
• THE PANCREAS IS BOTH ENDOCRINE AND
EXOCRINE
• THE EXOCRINE PANCREAS SECRETES DIGESTIVE
ENZYMES AND AN AQUEOUS ALKALINE FLUID
• PANCREATIC SECRETION IS HORMONALLY
REGULATED
• PANCREATIC SECRETIONS REACH THE SMALL
INTESTINE VIA THE COMMON BILE DUCT
THE EXOCRINE PANCREAS
SECRETES DIGESTIVE ENZYMES
• PROTEOLYTIC ENZYMES
• PANCREATIC AMYLASE
• PANCREATIC LIPASE
HORMONAL CONTROL OF
PANCREATIC SECRETION
• ACID IN DUODENAL LUMEN >SECRETIN:
STIMULATES PANCREATIC DUCT CELLS TO
PRODUCE SIGNIFICANT QUANTITES OF
AQUEOUS ALKALINE SECRETION
• FAT AND PROTEIN IN DUODENAL
LUMEN>CHOLECYSTOKININ
(CCK):STIMULATES PANCREATIC ACINAR
CELLS TO SECRETE DIGESTIVE ENZYMES
FUNCTIONS OF THE LIVER
• METABILIC PROCESSING OF ABSORBED
FOOD
• DETOXIFICATION2
• SYNTHESIS OF PLASMA PROTEINS
• STORAGE OF GLYCOGEN AND FAT, ETC.
• REMOVAL OF BACTERIA AND WORN-OUT
RBC
• EXCRETION OF CHOLESTEROL AND
BILIRUBIN
BILE SECRETION, STORAGE,
AND CIRCULATION
• SECRETED BY THE LIVER
• RECYCLED THROUGH
ENTEROHEPATIC CIRCULATION
• STORED IN GALL BLADDER
LIVER BLOOD FLOW
INFERIOR
VENA CAVA
AORTA
HEART
HEPATIC
VEIN
LIVER
HEPATIC
PORTAL
VEIN
HEPATIC
ARTERY
ARTERIES TO
DIGESTIVE TRACT
STOMACH
AND
SMALL
INTESTINE
BILE SALT CIRCULATION
LIVER
GALL BLADDER
SPHINCTER
OF ODDI
DUODENUM
S.I. MOTILITY
• SEGMENTATION CONTRACTIONS
• PACEMAKER CELLS
• MIXING AND PROPULSION
SEGMENTATION
CONTRACTIONS
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•
•
•
INITIATED BY PACEMAKER CELLS
MIXING ACTION
MOVES CHYME DOWNWARD
ILEOCECAL VALVE
S.I. SECRETIONS
• MANLY MUCOUS
• NO DIGESTIVE ENZYMES
DIGESTION
• MAINLY IN THE SMALL INTESTINE
• PANCREATIC ENZYMES
• BRUSH BORDER ENZYMES
ABSORPTION
•
•
•
•
LARGE SURFACE AREA
ACTIVE SODIUM TRANSPORT
FLUID AND ELECTROLYTES
SUGARS AND AA BY SECONDARY
ACTIVE TRANSPORT
• FAT
• VITAMINS AND MINERALS
LARGE SURFACE AREA
•
•
•
•
•
LONG TUBE
CIRCULAR FOLDS
VILLI
MICROVILLI
SIZE OF TENIS COURT
FLUID AND ELECTROLYTES
• SODIUM IS ACTIVELY TRANSPORTED ALONG
CELL’S BASOLATERAL MEMBRANE
• CHLORIDE FOLLOWS FOR ELECTRONEUTRALITY
• WATER FOLLOWS FOR OSMOTIC BALANCE
• POTASSIUM AND OTHER ELECTROLYTES ARE
MAINLY ABSORBED BY PASSIVE DIFFUSION
Absorption is a Function of the Epithelial Cells
Making up the Intestinal Wall
Lumen
Cells
Plasma
Sodium Absorption
PUMP: Na/K ATPase
Sodium
Lumen
Cells
Potassium
Plasma
Chloride
Water
AVERAGE DAILY INTAKE OF IRON
(NORTH AMERICA AND EUROPE)
• BETWEEN 10 AND 30 mg
• ABOUT 5 TO 7 mg PER 1000 CALORIES
• IF ON A 1000 TO 1500 CALORIE DIET,
ONLY 6-9 mg
• INFLUENCED BY COOKING UTENSILS
• DEPENDS ON BEVERAGE
CONSUMPTION
THE LARGE INTESTINE
• PRIMARILY A DRYING AND STORAGE
ORGAN
• HAUSTRAL CONTRACTIONS
• MASS MOVEMENTS
• PROTECTIVE SECRETIONS
• FORMATION OF FECES
THE DEFICATION REFLEX
• DISTENTION OF RECTUM
STIMULATES
• INTERNAL ANAL SPHINCTER
(SMOOTH MUSCLE) RELAXES
• EXTERNAL ANAL SPHINCTER
(SKELETAL MUSCLE) UNDER
VOLUNTARY CONTROL
GASTROINTESTINAL
HORMONES
• GASTRIN
• SECRETIN
• CHOLECYSTOKININ
GASTRIN
• ENDOCRINE CELLS IN PYLORIC STOMACH
• STIMULATED BY PROTEIN IN STOMACH
• STIMULATES SECRETION BY PARIETAL
AND CHIEF CELLS
• STIMULATES ILEAL MOTILITY
• RELAXES ILEOCECAL SPHINCTER
• INDUCES COLONIC MASS MOVEMENTS
SECRETIN
•
•
•
•
•
ENDOCRINE CELLS IN DUODENAL MUCOSA
ACID IN DUODENAL LUMEN
INHIBITS GASTRIC EMPTYING
INHIBITS GASTRIC SECRETION
STIMULATES AQUEOUS BICARBONATE
SECRETION BY PANCREAS
• STIMULATES BICARBONATE RICH BILE
SECRETION BYLIVER
CHOLECYSTOKININ
•
•
•
•
•
•
ENDOCRINE CELLS IN DUODENAL MUCOSA
FAT AND PROTEIN IN DUODENAL LUMEN
INHIBITS GASTRIC EMPTYING
INHIBITS GASTRIC SECRETION
CAUSES GALL BLADDER CONTRACTION
CAUSES RELAXATION OF THE SPHINCTER OF
ODDI
• CONTRIBUTES TO SATIETY
TOTAL BODY IRON IN
HUMANS
•
•
•
•
•
WEIGHT
SEX
SIZE OF STORAGE COMPARTMENT
HEMOGLOBIN CONCENTRATION
HISTORY
ABSORPTION OF IRON
FROM FOODS
% ABSO RBED
FO O D
D O S E (m g )
R IC E
2
1
S P IN A C H
2
2 -3
LETTU CE
17
3 -5
W HEAT
2 -4
5
VEAL
L IV E R
3
1 0 -1 8
F IS H
1 -2
1 0 -1 5
VEAL
M U SCLE
3 -4
20
H E M O G L O B IN
3 -4
1 0 -1 5
SOME DISEASES LINKED WITH DIET
•
•
•
•
•
CANCER
HEART DISEASE
HIGH BLOOD PRESSURE
OBESITY
DIVERTICULITIS
FOOD INGREDIENTS AND DISEASE
•
•
•
•
REFINED SUGAR
FAT
SALT
LOW IN FIBER
CANCER AND DIET: PHYTOCHEMICALS
•
•
•
•
FOUND ONLY IN PLANTS
IMMUNE FUNCTION
HORMONE BALANCE
DETOXIFICATION
CANCER AND DIET N.R.C.RECOMMENDATIONS
• EAT LESS FAT (30% OR LESS 0F TOTAL
CALORIES)
• EAT FRUITS, VEGITABLES, AND WHOLEGRAIN CEREAL FOODS EVERY DAY
(ESPECIALLY THOSE HIGH IN VITAMINS A
AND C)
• AVOID HIGH DOSE SUPPLIMENTS OF
VITAMINS OR OTHER NUTRIENTS
• ALCOHOL ONLY IN MODERATION
PROTEIN SOURCES-EXCEPTIONS
• SOYBEANS
• QUINONA
• SPINACH
• HAVE THE SAME QUALITY AS MILK
INCOMPLETE PROTEINS NEEDED TO MEET
REQUIREMENTS
•
•
•
•
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2 2/3 CUPS COOKED WHEAT
3 CUPS COOKED RICE
5 3/4 SLICES BASIC BREAD
3 CUPS DICED POTATOES
1/3 CUP SOY SPREAD
1/2 CUP WHEAT GERM
2 3/4 CUPS RICE WITH 1/3 CUP COOKED
PEAS
SOME WAYS TO CUT DOWN ON FAT
• EAT MORE VEGETARIAN MEALS
• EAT MORE FRESH FRUIT OR YOGURT
INSTEAD OF DESSERTS
• USE YOGURT AS DRESSING INSTEAD
OF OIL
• USE FRESH HERBS INSTEAD OF
BUTTER (AND INSTEAD OF SALT)
FIBER
• ROUGHLY SPEAKING, EVERYTHING IN
PLANT FOODS OUR DIGESTIVE ENZYMES
CAN NOT BREAK DOWN
• NURTURES AEROBIC BACTERIA IN GUT
• SOLUABLE FIBER REDUCES INSULIN NEED
IN DIABETICS
• CHELATORS-INCREASE NEED FOR
MINERALS
TYPES OF FIBER
• PECTINS: IN CELL WALL OF FRUITS, BIND BILE
SALTS
• GUMS: STICKY SUBSTANCES EXUDED BY
PLANTS, LOWER CHOLESTEROL UPTAKE AND
SLOW SUGAR ABSORPTION
• CELLULOSE: PLANT CELL WALLS, BULK AND
TOXIN ELIMINATION
• HEMICELLULOSES: PLANT CELL WALLS, BULK
• LIGNIN: ROOT VEGETABLES, BULK
EFFECT ON MICROFLORA
• LOWER TOTAL ANAEROBIC, IN
PARTICULAR, CLOSTRIDIUM
• DIET CAN ALTER THE METABOLIC
ACTIVITY OF THE FLORA
• MEAT AND UNREFINED SUGAR
INCREASES UNWANTED BACTERIA
• VEGETARIAN DIET LOWERS RISKS
OF BOWEL CANCER
RECOMMENDED FIBER INTAKE
• 20 - 25 g/day WITH AN UPPER LIMIT OF
35 g/day
• FAMILY HISTORY OF DIETIMPLICATED CANCER 35-40 g/day
• DIABETICS UP TO 50 g/day
SOURCES OF FIBER
• LEGUMES (ALSO PROTEIN SOURCE)
• FRUITS AND VEGETABLES
• WHOLE GRAIN CEREALS AND
FLOURS
SOLUABLE AND INSOLUABLE DIETARY FIBER
• SOLUABLE
• SOME
HEMICELLULOSE
• PECTIN
• GUM
• MUCILAGES
•
•
•
•
INSOLUABLE
LIGNIN
CELLULOSE
SOME
HEMICELLULOSE
CHELATORS LOWER MINERAL ABSORPTION
• PHYTATES
• OXALATES
SUPPLIMENTS FROM PLANTS
• ECHINACEA: IMMUNE BOOSTING AND
ANTIBIOTIC
• PSYLLIUM SEEDS: SOURCE OF FIBER
• CHAMOMILE: MILD SEDATIVE
• ALOE VERA: PROMOTES HEALING
• SAW PALMETTO EXTRACT: PROSTATE PROBLEMS
• GREEN TEA: ANTI CANCER , ANTIOXIDENT
• GARLIC: ANTIBACTERIAL, ANTIVIRAL, LOWERS
CHOLESTEROL
