THE DIGESTIVE SYSTEM II

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THE DIGESTIVE SYSTEM II

• D. C. Mikulecky
• Faculty Mentoring Program
• Virginia Commonwealth University

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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

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THE EXOCRINE PANCREAS SECRETES DIGESTIVE ENZYMES

• PROTEOLYTIC ENZYMES
• PANCREATIC AMYLASE
• PANCREATIC LIPASE

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HORMONAL CONTROL OF PANCREATIC SECRETION

• ACID IN DUODENAL LUMEN gtSECRETIN STIMULATES
  PANCREATIC DUCT CELLS TO PRODUCE SIGNIFICANT
  QUANTITES OF AQUEOUS ALKALINE SECRETION
• FAT AND PROTEIN IN DUODENAL LUMENgtCHOLECYSTOKININ
  (CCK)STIMULATES PANCREATIC ACINAR CELLS TO
  SECRETE DIGESTIVE ENZYMES

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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

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BILE SECRETION, STORAGE, AND CIRCULATION

• SECRETED BY THE LIVER
• RECYCLED THROUGH ENTEROHEPATIC CIRCULATION
• STORED IN GALL BLADDER

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LIVER BLOOD FLOW
INFERIOR VENA CAVA
AORTA
HEART
HEPATIC VEIN
HEPATIC ARTERY
LIVER
HEPATIC PORTAL VEIN
ARTERIES TO DIGESTIVE TRACT
STOMACH AND SMALL INTESTINE
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BILE SALT CIRCULATION
LIVER
GALL BLADDER
SPHINCTER OF ODDI
DUODENUM
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S.I. MOTILITY

• SEGMENTATION CONTRACTIONS
• PACEMAKER CELLS
• MIXING AND PROPULSION

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SEGMENTATION CONTRACTIONS

• INITIATED BY PACEMAKER CELLS
• MIXING ACTION
• MOVES CHYME DOWNWARD
• ILEOCECAL VALVE

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S.I. SECRETIONS

• MANLY MUCOUS
• NO DIGESTIVE ENZYMES

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DIGESTION

• MAINLY IN THE SMALL INTESTINE
• PANCREATIC ENZYMES
• BRUSH BORDER ENZYMES

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ABSORPTION

• LARGE SURFACE AREA
• ACTIVE SODIUM TRANSPORT
• FLUID AND ELECTROLYTES
• SUGARS AND AA BY SECONDARY ACTIVE TRANSPORT
• FAT
• VITAMINS AND MINERALS

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LARGE SURFACE AREA

• LONG TUBE
• CIRCULAR FOLDS
• VILLI
• MICROVILLI
• SIZE OF TENIS COURT

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FLUID AND ELECTROLYTES

• SODIUM IS ACTIVELY TRANSPORTED ALONG CELLS
  BASOLATERAL MEMBRANE
• CHLORIDE FOLLOWS FOR ELECTRONEUTRALITY
• WATER FOLLOWS FOR OSMOTIC BALANCE
• POTASSIUM AND OTHER ELECTROLYTES ARE MAINLY
  ABSORBED BY PASSIVE DIFFUSION

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Absorption is a Function of the Epithelial Cells
Making up the Intestinal Wall
Plasma
Lumen
Cells
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Sodium Absorption
PUMP Na/K ATPase
Plasma
Sodium
Lumen
Cells
Potassium
Chloride
Water
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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

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THE LARGE INTESTINE

• PRIMARILY A DRYING AND STORAGE ORGAN
• HAUSTRAL CONTRACTIONS
• MASS MOVEMENTS
• PROTECTIVE SECRETIONS
• FORMATION OF FECES

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THE DEFICATION REFLEX

• DISTENTION OF RECTUM STIMULATES
• INTERNAL ANAL SPHINCTER (SMOOTH MUSCLE) RELAXES
• EXTERNAL ANAL SPHINCTER (SKELETAL MUSCLE) UNDER
  VOLUNTARY CONTROL

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GASTROINTESTINAL HORMONES

• GASTRIN
• SECRETIN
• CHOLECYSTOKININ

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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

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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

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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

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TOTAL BODY IRON IN HUMANS

• WEIGHT
• SEX
• SIZE OF STORAGE COMPARTMENT
• HEMOGLOBIN CONCENTRATION
• HISTORY

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ABSORPTION OF IRON FROM FOODS
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SOME DISEASES LINKED WITH DIET

• CANCER
• HEART DISEASE
• HIGH BLOOD PRESSURE
• OBESITY
• DIVERTICULITIS

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FOOD INGREDIENTS AND DISEASE

• REFINED SUGAR
• FAT
• SALT
• LOW IN FIBER

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CANCER AND DIET PHYTOCHEMICALS

• FOUND ONLY IN PLANTS
• IMMUNE FUNCTION
• HORMONE BALANCE
• DETOXIFICATION

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CANCER AND DIET N.R.C.RECOMMENDATIONS

• EAT LESS FAT (30 OR LESS 0F TOTAL CALORIES)
• EAT FRUITS, VEGITABLES, AND WHOLE-GRAIN 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

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PROTEIN SOURCES-EXCEPTIONS

• SOYBEANS
• QUINONA
• SPINACH
• HAVE THE SAME QUALITY AS MILK

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INCOMPLETE PROTEINS NEEDED TO MEET REQUIREMENTS

• 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

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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)

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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

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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

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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

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RECOMMENDED FIBER INTAKE

• 20 - 25 g/day WITH AN UPPER LIMIT OF 35 g/day
• FAMILY HISTORY OF DIET-IMPLICATED CANCER 35-40
  g/day
• DIABETICS UP TO 50 g/day

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SOURCES OF FIBER

• LEGUMES (ALSO PROTEIN SOURCE)
• FRUITS AND VEGETABLES
• WHOLE GRAIN CEREALS AND FLOURS

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SOLUABLE AND INSOLUABLE DIETARY FIBER

• SOLUABLE
• SOME HEMICELLULOSE
• PECTIN
• GUM
• MUCILAGES

• INSOLUABLE
• LIGNIN
• CELLULOSE
• SOME HEMICELLULOSE

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CHELATORS LOWER MINERAL ABSORPTION

• PHYTATES
• OXALATES

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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