The Digestive System

1. The Digestive System Chapter 48

2. Introduction Digestion is the mechanical and chemical breakdown of food into forms that cells can absorb. The FUNCTIONs of the Digestive System include Breakdown food Convert it into a usable form Form and expel solid wastes

3. Human digestivesystem

4. The Alimentary Canal If stretched out, the alimentary canal is about 8 meters long. That’s 26 feet!

5. OVERVIEW https://www.youtube.com/watch?v=nM5kMSjBrmw

6. The Mouth (ORAL CAVITY) • The mouth: • Receives food • Mechanically breaks up solid particles using TEETH & TONGUE • Chemically digest food using saliva. • This action is called mastication • Makes a BOLUS (wet ball of food) • The mouthalso functions as an organ of speech, and sensory reception.

7. Teeth & TONGUE • TEETH • Incisors- bite or cut off • Canines- grasp and tear • Premolars – grinding food • Molars – grinding food • TONGUE • Position food between teeth • Push food back to pharynx

8. Salivary Glands • Secrete saliva • Saliva moistens the food, and begins the digestion of carbohydrates Three pairs of major salivary glands.

9. The palate and uvula During swallowing, muscles draw the soft palate and the uvula upward preventing food from entering the nasal cavity.

10. Pharynx • The back of the throat. • Deglutition (swallowing)

11. Swallowing • Epiglottis • flap of cartilage • closes trachea (windpipe) when swallowing • food travels down esophagus

12. esophagus • Moves food down to stomach by peristalsis • involuntary muscle contractions to move food along

13. Stomach • 2 sphincters (valves) • 3 layers of muscle • Secretes gastric juices (enzymes + HCl) • Mechanically and chemically breaks down food

14. Gastric Juice • Acidic (pH 1.5-2.5) (HCl) • Pepsin- an enzyme that breaks down large proteins into aminoacids. • HCl activates pepsin • BOLUS + GASTRIC JUICE = chyme.

15. Heartburn • Acid Reflux

17. Accessory organs

18. Accessory Organs • Pancreas • Gall Bladder • Liver

19. Pancreas Secretes pancreatic juice which contains enzymes to digest all major nutrient types. • Alkaline (base) neutralizes acidic chyme coming from stomach.

20. LIVER

21. Liver • Function: produces bile • BILE breaks up fats

22. GALL BLADDER • It stores bile between meals • Bile duct – • Connects the liver, pancreas, and gall bladder to the duodenum (small intestine)

23. GALLSTONES • GALLSTONES – an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder • Can either be “passed” (OUCH!!) or surgically removed

24. Small intestine • Function • Digestion & absorption • over 6 meters! • small intestine has huge surface area ~size of tenniscourt • Structure • 3 sections • duodenum= most digestion • jejunum= absorption of nutrients & water • ileum = absorption of nutrients & water

25. Absorption in the SI • Much absorption is thought to occur directly through the wall without the need for special adaptations • Almost 90% of our daily fluid intake is absorbed in the small intestine. • Villi- increase the surface area of the small intestines, thus providing better absorption of materials

26. Villi increase surface area. More surface area = More absorption

27. Large intestines (colon) • Function • re-absorb water • use ~9 liters of water every day in digestive juices • > 90% of water reabsorbed

28. Large Intestine • Solid materials pass through the large intestine. • These are undigestible solids (fibers). • Water is absorbed. • Vitamins K and B are reabsorbed with the water. • Rectum- solid wastes exit the body.

29. Bacterial flora • Living in the large intestine is a community of helpful bacteria • Escherichiacoli (E. coli) • produce vitamins • vitamin K; B vitamins • generate gases • by-product of bacterial metabolism • methane, hydrogen sulfide

30. feces • Poop, excrement, solid waste, etc… • Feces is composed of materials not digested or absorbed, and include: Water, Electrolytes, Mucus, Bacteria, and Bile pigments • Approximately 1/3 of the dry weight of feces is bacteria. • The color of feces is provided by bile pigments altered by bacteria .

31. diarrhea • a gastrointestinal disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine. • This results in increased, multiple, watery feces. • This condition may result in severe dehydration, especially in infants

32. constipation • a condition in which the large intestine is emptied with difficulty • Too much water is reabsorbed • Solid waste hardens

33. Rectum • Last section of colon (large intestines) • eliminate feces • undigested materials • extracellular waste • mainly cellulose from plants • roughage or fiber • masses of bacteria

34. Anal Canal / Anus… Last Stop • Exit or opening for solid wastes • Regulated by anal sphincter (valve) • Anal sphincter surrounded by muscles • Elimination aided by abdominal muscles

35. Hemorrhoids • Very common, especially during pregnancy and after childbirth. • Result from increased pressure in the veins of the anus. The pressure causes the veins to bulge and expand, making them painful, particularly when you are sitting.. Symptoms • Anal itching • Anal ache or pain, especially while sitting • Bright red blood on toilet tissue, stool, or in the toilet bowl Pain during bowel movements One or more hard tender lumps near the anus