DIGESTIVE SYSTEM

1. DIGESTIVE SYSTEM

2. DIGESTIVE TRACT • Tube in which digestion occurs • Also called alimentary canal, gastrointestinal tract (GI) • Entire canal is about 9 meters along (30 feet) in a cadaver. Shorter in a live person

3. FUNCTIONS • Ingest food • Break down nutrients to a form that can cross plasma membranes • Absorb nutrients • Eliminate undigested parts

4. PARTS

5. ORAL CAVITY • Mouth - receives food • Lips (labia) protects opening • Tongue – taste buds, pushes food to back of throat fermium – a fold of mucous membrane that secures the tongue to the floor of the mouth • Roof of mouth – contains made up of: 1. hard palate -anterior portion is bone 2. Soft palate posterior portion is muscle

6. Parts continued • Uvula – finger-like projection that closes off nasopharynx keeps food from entering the nasal cavity • Tonsils – protects against injection

7. SALIVARY GLANDS • 3 pairs • secrete saliva • contains enzyme salivary amylase starts digestion of starch feel flaps under tongue and cheeks – where ducts are located • Contains substances that inhibit bacteria growth • Dissolves food chemicals so they can be tastes

8. Teeth – mechanical digestion

9. PHARYNX – region that receives food and air • Trachea – also called windpipe lies in front of esophagus • Swallowing is a reflex • Glottis – opening to the larynx • Epiglottis – spoon shaped tissue covering a piece of cartilage covers glottis so food/liquids do not enter trachea

10. ESOPHAGUS • Muscular tube • Connects to stomach • Remains collapsed until bolus enters • Peristalsis – rhythmic contractions that push food along digestive tract • No chemical digestion occurs

11. LAYERS OF GI TRACT • Mucosa – inner most – moist membrane that lines the lumen • Submucosa- beneath mucosa- made up of connective tissue, and lymph vessels • Muscularis external - smooth muscles • Serosa – outermost layer

12. Esophagus continued • Sphincters – muscles that encircle a tube act as valves • located at point where stomach and esophagus meet • when open – food passes into stomach • closed – keeps acid from entering esophagus

13. STOMACH • Thick muscular wall • Wall has deep folds called rugae • Holds 4 liters when full • Stores food • Empties in 2/6 hours • Mechanical digestion – churns and mixes food with gastric juices • pyloric sphincter connects to small intestine • Cardioesophageal sphincter – connects to esophagus

14. REGIONS OF STOMACH • Fundus – expanded part of the stomach • Body – the midportion • Pylorus – terminal part of stomach

15. GASTRIC JUICES • Pepsin – digests protein • HCL – hydrochloric acid pH 2 kills bacteria breaks down connective tissue of meat activates pepsin • Mucus • Intrinsic factor – substance needed for the absorption of vitamin B12 in the small intestine

16. MUCUS • Thick layer of mucus • Protects stomach from HCL • Produced by goblet cells • Ulcer – open sore in wall of stomach exposed to gastric juices bacterial infection interferes with mucus production

17. STOMACH CONTINUED • Chyme – contents of stomach thick soupy liquid enters small intestines in small squirts • No absorption of food occurs in stomach • Alcohol absorption only

18. SMALL INTESTINE • Major site of digestion • Has small diameter • About 3 meters (9 feet) long

19. THREE PARTS OF SMALL INTESTINE • Duodenum – 1st part of small intestine • sphincter muscles control chyme entering • receives enzymes from liver and pancreas • Jejunum • Ileum – terminal part of intestine • Ends with the ileocecal valve

20. WALL OF SMALL INTESTINE • Fingerlike projections called villi • Microscopic microvilli absorb sugars and amino acids directly into blood stream • Components of fats enter smooth ER where they are rejoined and enter the lacteal (small lymphatic vessels)

21. LARGE INTESTINE • 1.5 Meters • Absorbs water, salts, and vitamins • Parts: cecum colon rectum

22. CECUM • Lind end of large intestine • Appendix – small projection may help fight infection subject to inflammation

23. COLON • Ascending • Transverse • Descending • Sigmoid colon – enters rectum

24. RECTUM • 20 cemeters • Anus – opening to outside expels feces • Stretching of rectal wall sends nerve impulses to spinal cord causing relaxation of anal sphincters • Bacteria found in some feces produce vitamins that are reabsorbed by our body

25. PANCREASE • Endocrine functions involves insulin and glucagon • Exocrine function involves the secretion of pancreatic juices

26. PANCREATIC JUICES • Sodium bicarbonate • NaHCO3 • Neutralizes chyme • Pancreatic amylase • Digest starch • Trypsin • Digest proteins • Lipase • Digest fats

27. LIVER • Responsible for maintaining homeostasis of blood • Removes poisonous substances • Removes Fe and stores it • Removes Vitamins A,D,E and K and stores them • Makes plasma proteins to maintain osmotic pressure

28. LIVER CONTINUED • Makes cholesterol and regulates amount in blood • Maintains blood glucose levels • Produces bile which emulsifies fat • Produces fact

29. GALL BLADDER • Sac attached to undersurface of liver • Stores bile until needed in the duodenum • Gall stones - cholesterol comes out of bile solution forming crystals

30. Feces – more or less solid product delivered to the rectum • Resident bacteria of large intestine metabolize the remaining material • Gases are released • Methane and hydrogen sulfide produce the odor – more gas is produced when food is high in carbohydrates • Bacteria make vitamin K and some B vitamins

32. Acid reflux Appendicitis Cirrhosis Colorectal cancer Colostomy Constipation Diarrhea Gallstones Hemorrhoids Hepatitis Hernia IBS Jaundice Lactose intolerance Mumps Peritonitis Ulcer Vomiting DISEASES OF THE GI TRACT