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THE DIGESTIVE SYSTEM
• BODY CELLS REQUIRE A CONTINUOUS
SUPPLY OF NUTRIENTS THAT COME
FROM INGESTED FOOD.
• FOOD MOLECULES ARE TOO LARGE TO
PASS DIRECTLY INTO BLOOD AND MUST
BE BROKEN INTO SMALLER MOLECULES.
• DIGESTION OF FOOD & ABSORPTION OF
NUTRIENTS ARE THE MAJOR FUNCTIONS
OF THE DIGESTIVE SYSTEM.
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DIGESTIVE SYSTEM STRUCTURE
• CONSIST OF A LONG TUBE & ACCESSORY
ORGANS ASSOCIATED WITH IT.
• THE SHAPE OF EACH PART IS MODIFIED
ACCORDING TO ITS FUNCTION.
• PARTS:- MOUTH, PHARYNX, ESOPHAGUS,
STOMACH, SMALL INTESTINE, LARGE
INTESTINE AND ANUS.
• ACCESSORY ORGANS:- TEETH, SALIVARY
GLANDS, LIVER AND PANCREAS.
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DIGESTIVE SYSTEM STRUCTURE
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WALL STRUCTURE
• SEROSA:- THE OUTERMOST LAYER MADE OF A
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SEROUS MEMBRANE & CONNECTIVE TISSUES.
ALSO CALLED THE VISCERAL PERITONIUM.
MUSCULAR LAYER:- MADE OF TWO CIRCULAR &
LONGITUDINAL SMOOTH MUSCLE LAYERS.
SUBMUCOSA:- MADE OF LOOSE CONNECTIVE
TISSUE CONTAINING NERVES, GLANDS, BLOOD
AND LYMPHATIC VESSELS.
MUCOSA:- MADE OF EPITHELIUM, CONNECTIVE
TISSUE AND SOME SMOOTH MUSCLE FIBERS.
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WALL STRUCTURE
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THE MOUTH
• FORM THE ORAL CAVITY WHICH IS
INVOLVED IN THE INTAKE OF FOOD,
BREAKING IT, MIXING IT WITH SALIVA
AND SWALLOWING IT.
• CONTAIN THE TEETH & IS SURROUNDED
BY THE CHEEKS, PALATE & TONGUE.
• MECHANICAL DIGESTION BY CHEWING.
• CHEMICAL DIGESTION BY SALIVARY
AMYLASE ENZYME.
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THE MOUTH
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THE TEETH
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THE SALIVARY GLANDS
• THEY SECRETE SALIVA THAT CLEAN &
LUBRICATE THE MOUTH, DISSOLVE, BIND
AND DIGEST FOOD PARTICLES.
• PAROTID GLANDS:- IN FRONT OF EAR.
SECRETE AMYLASE ENZYME.
• SUBMANDIBULAR GLANDS:- IN FLOOR OF
THE MOUTH.
• SUBLINGUAL GLANDS:- UNDER TONGUE.
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SALIVARY GLANDS
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PHARYNX & ESOPHAGUS
• THE PHARYNX TRANSPORT FOOD FROM
THE MOUTH TO THE ESOPHAGUS.
• THE ESOPHAGUS IS A MUSCULAR TUBE
THAT CARRY FOOD FROM THE PHARYNX
INTO THE STOMACH.
• HAS AN UPPER ESOPHAGIAL SPHINCTER
AND A LOWER ESOPHAGIAL SPHINCTER.
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PHARYNX & ESOPHAGUS
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THE STOMACH
• A POUCHLIKE PART OF THE DIGESTIVE
SYSTEM THAT FUNCTION FOR STORAGE,
MIXING AND DIGESTION OF FOOD.
MADE OF FOUR REGIONS:• CARDIAC – FUNDIC – BODY – PYLORIC
• ENTERANCE IS GUARDED BY THE LOWER
ESOPHAGIAL SPHINCTER WHILE EXIT IS
GUARDED BY THE PYLORIC SPHINCTER.
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THE STOMACH
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THE STOMACH
• A THICK FOLDED MEMBRANE COATED
WITH MUCUS LINE THE STOMACH.
• GASTRIC GLANDS SECRETE DIGESTIVE
ENZYMES & HYDOCHLORIC ACID.
• PEPSIN ENZYME START THE DIGESTION
OF PROTEINS TO FORM SMALL PEPTIDES
• HYDROCHLORIC ACID ACTIVATE PEPSIN
& KILL ANY MICROORGANISMS IN FOOD.
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GASTRIC GLANDS
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CONTROL OF GASTRIC SECRETIONS
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THE PANCREAS
• THE EXOCRINE PANCREAS SECRETES
PANCREATIC JUICE INTO DUODENUM
PART OF THE SMALL INTESTINE.
• PANCREATIC JUICE CONTAIN DIGESTIVE
ENZYMES & A BICARBONATE SOLUTION.
• PANCREATIC AMYLASE:CARBOHYDRATES DIGESTION.
• PANCREATIC LIPASE:- FATS DIGESTION.
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• TRYPSIN:- PROTEINS DIGESTION.
THE PANCREAS
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CONTROL OF PANCREATIC SECRETIONS
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THE LIVER
• IS THE LARGEST GLAND IN THE BODY.
FUNCTIONS:• CLEANS HARMFUL CHEMICALS, DRUGS
AND DEAD CELLS FROM THE BLOOD.
• STORES FATS, GLYCOGEN, MINERALS &
VITAMINS.
• SECRETES BILE THAT BREAKS THE LARGE
FAT DROPS INTO SMALLER PARTICLES &
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HELP THEIR ENZYMATIC DIGESTION.
THE LIVER
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THE GALLBLADDER
• BILE IS STORED IN THE GALLBLADDER.
• WHEN FATTY FOOD ENTER DUODENUM,
CHOLECYTOKININ {CCK} HORMONE IS
SECRETED BY THE INTESTINAL CELLS.
• {CCK} STIMULATES THE GALLBLADDER
WALLS CONTRACTION TO EMPTY BILE
INTO THE DUODENUM.
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THE GALLBLADDER
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THE SMALL INTESTINE
• A LONG TUBE EXTENDING BETWEEN THE
STOMACH AND THE LARGE INTESTINE.
• ENTRANCE IS GUARDED BY THE PYLORIC
SPHINCTER WHILE EXIT IS GUARDED BY
THE ILEOCECAL SPHINCTER.
• CONSIST OF THREE PARTS:• DUODENUM – JEJUNUM – ILEUM
• MOST OF DIGESTION & ABSORPTION OF
FOOD OCCUR IN THE SMALL INTESTINE. 26
THE SMALL INTESTINE
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SMALL INTESTINE HORMONES
• GASTRIN:- STIMULATE GASTRIC GLANDS
SECRETION.
• CHOLECYSTOKININ {CCK}:INHIBIT GASTRIC GLANDS SECRETION,
STIMULATE PANCREATIC SECRETION &
GALLBLADDER CONTRACTION.
• SECRETIN:- INHIBIT GASTRIC GLANDS
SECRETION & STIMULATE PANCREATIC
JUICE SECRETION.
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SMALL INTESTINE ENZYMES
• MALTASE DIGEST MALTOSE TO GLUCOSE
• SUCRASE DIGEST SUCROSE TO GLUCOSE
AND FRUCTOSE.
• LACTASE DIGEST LACTOSE TO GLUCOSE
AND GALACTOSE.
• LIPASE DIGEST FATS TO FATTY ACIDS.
• PEPTIDASE DIGEST SMALL PEPTIDES TO
SINGLE AMINO ACIDS.
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ABSORPTION
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THE LARGE INTESTINE
• EXTEND FROM THE ILEUM TO THE ANUS
AND IS MADE OF THREE SEGMENTS:• CECUM – COLON – RECTUM.
• FUNCTION FOR ABSORPTION OF WATER,
MINERALS AND VITAMINS.
• ENTRANCE GUARDED BY THE ILEOCECAL
SPHINCTER WHILE THE ANAL EXIST IS
GUARDED BY INTERNAL AND EXTERNAL
ANAL SPHINCTERS.
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THE LARGE INTESTINE
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THE RECTUM & ANAL CANAL
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FOOD ENERGY
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