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Digestive System

Digestive System. P & A. I. Intro to Digestive System. A. Function: to process food into forms that can be absorbed by the cell membranes. B. Includes: Alimentary Canal Tube from mouth to anus Accessory Organs Structures which secrete into A.C.

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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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