1. CHAPTER 15 DIGESTIVE SYSTEM
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2. 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.

3. 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.

4. DIGESTIVE SYSTEM STRUCTURE

5. WALL STRUCTURE
SEROSA:- THE OUTERMOST LAYER MADE OF A 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.

6. WALL STRUCTURE

7. 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.

8. THE MOUTH

9. THE TEETH

10. 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.

11. SALIVARY GLANDS

12. 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.

13. PHARYNX & ESOPHAGUS

14. 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.

15. THE STOMACH

16. 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.

17. GASTRIC GLANDS

18. CONTROL OF GASTRIC SECRETIONS

19. 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.
TRYPSIN:- PROTEINS DIGESTION.

20. THE PANCREAS

21. CONTROL OF PANCREATIC SECRETIONS

22. 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 & HELP THEIR ENZYMATIC DIGESTION.

23. THE LIVER

24. 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.

25. THE GALLBLADDER

26. 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.

27. THE SMALL INTESTINE

28. 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.

29. 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.

30. ABSORPTION

31. 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.

32. THE LARGE INTESTINE

33. THE RECTUM & ANAL CANAL

34. FOOD ENERGY