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Digestive System

Discover the components and functions of the digestive system, from the alimentary canal to accessory organs. Explore the types of digestion and the role of the mouth, teeth, salivary glands, pharynx, esophagus, and stomach.

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Digestive System

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  1. Digestive System P & A

  2. I. Intro to Digestive System • A. Function: to process food into forms that can be absorbed by the cell membranes

  3. B. Includes: • Alimentary Canal • Tube from mouth to anus • Accessory Organs • Structures which secrete into A.C. • Salivary glands, liver, pancreas, gall bladder

  4. II. Alimentary Canal • A. Structure • 9 m. long • Includes: mouth, pharynx, esophagus, stomach, small intestine, large intestine

  5. 1. wall of canal (inside out) • A. mucosa – functions to absorb and secrete • S: • Inner layer of wall • Made up of: epithelial tissue, connective tissue, and smooth muscle • Has projections which extend into canal to increase surface area • Has glands to secrete mucous and enzymes • F: • Absorb & secrete

  6. B. submucosa • Outside mucosa • S: • Loose connective tissue, blood vessels, lymph vessels, nerves • F: • Blood nourishes surrounding tissue & carries away absorbed nutrients by mucosa

  7. Muscular layer • S: • Outside submucosa • Includes circular & long muscles • Made up of muscle tissue • F: • To constrict/elongate to move food down tube

  8. Serosa • S: • Outer covering • Visceral peritoneum: moist, slimy tissue • F: • To secrete fluid so that canal stays lubricated to slide by other organs in the DS

  9. 2. Movement • A. mixing by smooth muscles contracting in small segments of canal • B. peristalsis • Wavelike contractions of tract that moves food downward

  10. III. Types of Digestion • A. chemical • Involves enzymes breaking down food into usable substances for cells • Chemicals enter blood for body to use

  11. B. mechanical • Chewing food into smaller pieces for the system to break down further

  12. C. physical • Peristalsic mixing • Stomach churning

  13. IV. Mouth/Oral Cavity • Center of mechanical digestion • Reduces food size • Mixes food with saliva

  14. A. cheeks and lips • Cheeks used for chewing • Lips judge temp & texture of food

  15. B. tongue • 1. frenulum • Membranous fold which connects floor of mouth to tongue • 2. very muscular – moves food to pharynx • 3. has papillae - tastebuds

  16. C. lingual tonsils • Rounded masses of lymphatic tissue at base of tongue • ** NOT the ones you get removed

  17. D. Palate • A. hard palate top/front portion of mouth • B. soft palate top/back portion of mouth • C. uvula – sac of tissue extending off the soft palate which closes the nasal cavity while swallowing • D. palantine tonsils: • Back of mouth on either side of tongue • Lymphatic tissue that fights disease • ** GET THESE OUT

  18. E. teeth • A. primary: 20 teeth • Come b/n 6 months & 2 yrs • B. secondary: 32 teeth • Come b/n 6 yrs & 23 yrs

  19. C. teeth types • Incisors: 8 (4 front top and bottom) • Cut food into smaller pieces • Cuspid: 4 • Canines that cut and tear food • Bicuspids: 8 • Premolars • Molars: 12 • Crush and grind food • Wisdom teeth: 4 (don’t always get)

  20. F. Salivary glands • Function: secrete saliva to moisten food, bind food together, and digest carbs • A. secretions: • Amylase • Enzyme that breaks down carbs

  21. B. parotid glands • - largest salivary gland • - lies in front of and below each ear • C. submandibular glands • On floor of mouth • D. sublingual glands • Smallest salivary glands under the tongue

  22. E. psychological stimulus • Think about food and salivate • F. mechanical stimulus • Action of chewing stimulates salivation

  23. V. Pharynx • A. pharynx • Connects nasal and oral cavities • Very short • 1. nasopharynx • Provides passageway for air for breathing • 2. oropharynx • Passageway for food • 3. laryngopharynx • Opens into larynx & esophagus

  24. B. swallowing process • 1. soft palate/uvula is raised closing nasal cavity so food cannot enter • 2. hyoid bone (front of larynx) & larynx are raised so food doesn’t enter trachea • 3. EPIGLOTTIS is pressed down by the tonue closing the trachea

  25. 4. muscles in pharynx relax, opening esophagus • 5. peristalsic motion of esophagus begins forcing food down to stomach • ** during this process breathing is stopped

  26. VI. Esophagus • A. Structure • Straight, collapsible tube • 25 cm long • Located behind trachea • Connects pharynx to stomach

  27. Inner layer (mucosa) has much mucous to keep food lubricated to keep traveling smoothly • Strong muscles at base to keep stomach contents from coming up

  28. B. Function • Move food to stomach • Keep food moist & lubricated

  29. VII. Stomach • A. structure • J-shaped • Under diaphragm • Inner lining: RUGAE • Thick folds which increase surface area for absorption

  30. B. function • Mixing food w/ gastric juice rich in enzymes • Begins protein digestion • Absorbs smalls amounts of nutrients

  31. C. special parts • 1. cardiac region • Small area right off espophagus • 2. fundic region • “puffy” part – greater curve

  32. 3. pyloric region • Narrow – lesser curve • Leads to small intestine • 4. pyloric sphinctor • Thick muscle at end of pyloric region which prevents contents of sm. Intestine from going back into stomach

  33. 5. cardioesophagealsphinctor • Prevents food from going back into esophagus • 6. serosa • Protective inner lining • Secretes mucous to protect stomach inner lining from gastric acids

  34. D. secretions • 1. digestive enzymes • Pepsin & pepsinogen – split proteins • Sucrase, maltase, lactase – split sugars • Lipase – split fat

  35. 2. hydrochloric acid • Enzymes need acid environment to work on proteins • 3. intrinsic factor • Lets vitamin B12 be absorbed by small intestine • *****These 3 make up gastric juice

  36. E. stomach contents • 1. as stomach mixes food with gastric juice = CHYME is produced • Food + gastric juice in pasty form • 2. liquids pass through stomach quickly • 3. foods high in carbs pass fastest

  37. 4. foods high in proteins pass next fastest • 5. fatty foods remain 4-6 hrs

  38. VII. Pancreas • A. Structure • C-shaped organ • Pancreatic duct runs through it • B. Function • Production of pancreatic juice which flows pancreatic duct to sm. intestine

  39. C. pancreatic juice • Enzymes which break down: work when they get to small intestine • Carbs– pancreatic amylase • Proteins – trypsin, chymostrypsin, carboxypeptidase • Fats – pancreatic lipase • Nucleic acids - nucleases

  40. VIII. Liver • A. intro • Located below diaphragm • Mostly covered by ribs • Reddish- brown • Many blood vessels • 2 lobes

  41. B. functions • 1. regulation of blood glucose level • Can change glycogen to glucose, glucose to glycogen, or non-carbs to glucose • 2. synthesis of fats

  42. 4. stores glycogen, vit A, D, B12 • 5. destroys damaged RBCs • 6. detoxifies blood of toxins • 7. secretes bile

  43. D. Bile • Bile salts – does the actual digestion of fats • F: EMULSIFICATION • BREAKING DOWN OF FATS

  44. IX. Gall bladder • A. s: • Pear shaped sac attached to the liver • B. F: • Bile is stored here

  45. X. Small intestine • A. s: • Extends from stomach to L. intestine • Fills most of abdominal cavity

  46. Divided into 3 main parts: • A. duodenum: 12 in – biggest diameter • B. jejunum: 2 m – thickest wall • C. ileam: 3-4 m • Mesentery • Thin issue which holds sm. Intestine to body wall

  47. Intestinal villi • In duodenum and jejunum • Fingerlike projections which increase SA for absorption

  48. XI. Large Intestine • A. s: • 1.5 m long • Parts of LI: • Cecum – beginning pouchlike structure of LI • Vermiform appendix • Hangs off cecum • No digestive function • Contains lymphatic tissue for immune system

  49. Colon: 4 parts • Ascending – travels up to liver • Transverse – long, straight mobile part of LI • Descending – downward portion • Sigmoid – S-shaped curve which ends with rectum • Rectum • Attached to bottom of spine or tailbone • Muscular end of colon

  50. Anal canal • 2.5 – 4 cm long • Muscular tube at end of DT • Contains internal and external sphinctors which are under voluntary control to rid of waste

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