Lect 17Digestive Gastrointestinal Tract Accessory Organs Intro to Anatomy , Physiology and Nutrition

1. Lect 17DigestiveGastrointestinal TractAccessory OrgansIntro to Anatomy , Physiology and Nutrition

2. Digestive Tract = ___________ • Mouth • Pharynx • Esophagus • Stomach • Small Intestine • Large Intestine • Anus Accessory Organs • Teeth and salivary glands • Liver/gall bladder • Pancreas • Mesenteries

3. Alimentary Canal - Characteristic Cross Section • __________ = Passage down the middle • Mucosa • Submucosa • What kind of tissue? • What is found in this layer? • Muscle layer • Serosa = ? Type of membrane ____________

5. Functions of the Digestive System • The process of taking foods and liquid into the mouth: • Ingestion • The release of water, acid, buffers, and enzymes by cells and accessory organs into the lumen. • Secretion • Alternating contraction and relaxation of smooth muscle. • Peristalsis  Mixing and propulsion • Mechanical and chemical break down of organic material into small molecules. • Digestion

6. Mouth • Cheeks: lateral walls • buccinator muscles, bucal fat pads • Non-keratinized stratified squamous epithelium • Lips attach to gum: labial frenulum (a midline fold) • Vestibule: space between lips and gums (gingiva)/teeth • Oral cavity proper – from gums and teeth to Fauces

8. Oral Cavity • Floor: • Mylohyoid muscle • Tongue • frenulum • Palate: • Hard Palate: palantine bones + part of maxilla • Soft Palate: + Uvula – close oral cavity nasopharynx • Tonsils: • Palatine: either side of tongue • Lingual : near base of tongue at hyoid bone • Pharyngeal: = adenoids – posterior wall of pharynx

10. Teeth • Fours types: • Incisors • Canines • Premolars • Molars • Primary teeth: deciduous – ‘baby teeth’ • Adult teeth • dental formula: number of teeth of each type in one half of each jaw reading from the front (incisors) to back (molars) • Humans Adults: 2123/2123

13. Salivary Glands • Parotid below your ear and over the masseter • Submandibular is under lower edge of mandible • Sublingual is deep to the tongue in floor of mouth • All have ducts that empty into the oral cavity Tortora & Grabowski 9/e 2000 JWS

14. Pharynx – 3 regions: Nasopharynx • Swallowing: • What prevents food from entering nasal cavity: • What temporarily seals oral cavity/pharynx? • What closes opening to respiratory passage? • Peristaltic wave pushes _______ down __________. Oropharynx Laryngopharynx

15. The Esophagus • Anatomy • A collapsible 10 inch long muscular tube. • Functions • Secrete mucus and transport food from the pharynx to the stomach. • Rhythmic waves of muscle contraction? (Peristalisis). • Pierces the diaphragm at hiatus • hiatal hernia or diaphragmatic hernia

16. Peritoneum • visceral layer covers organs • parietal layer lines the walls of body cavity • Peritoneal cavity • potential space containing a bit of serous fluid

17. Greater Omentum- fatty apron: covers transverse colon and small intestine.

18. Falciform Ligament: Suspends liver from anterior wall of abdomen/diaphragm • Lesser Omentum: suspends stomach and duodenum from liver • Mesentary Proper: Extends from dorsal wall of abdominal cavity, suspends small intestine • Mesocolon: binds transverse and sigmoid colon to dorsal abd. wall

19. Falciform Ligament Lesser Omentum Greater Omentum Mesentary Proper Mesocolon

20. Which side is it on? • Size when empty? • Parts of stomach? • Structure of its walls? • Smooth muscle layers • rugae • Gastric pits • What digestive processes occur here • Associated mesenteries? • Semifluid contents are known as?

21. Gastric Pits and Gastric Glands • Gastric Pits: shallow depressions of gastric mucosa • Gastric Glands: • Open to gastric pits • Endocrine and exocrine cells in walls • Exocrine secretions  gastric juice

22. Protects walls of stomach • Acid environment activates pepsinogen • Absoption o f B12 in small intestine • Initiates protein breakdown • Hormonal activity initiates smooth muscle action and secretion of gastric juice

23. What stimulates secretion of Gastrin?

24. Secretion of gastric juice – parasympathetic involvement – sensory stimuli

25. Small Intestine • Three parts • Digestive processes • Absorption of lipids •  • Special adaptations – functions • Support

27. Absorption in Small Intestine

28. Absorption of Lipids • Bile salts act to emulsify • Fatty acids + glycerol at villi • Intermediate metabolic conversions  chylomicrons – protein encased structures enter blood stream • Delivered to • tissues as LDL • Liver as HDL • Bile salts  feces

29. Where will the absorbed nutrients go?

30. Pancreas- Endocrine/Exocrine • Endocrine – Islet tissues • Exocrine – acinar cells via pancreatic duct  ?? (where) • Pancreatic juice: • Pancreatic amylase • Trypsin • Lipase etc. • Releases bicarbonate ions – neutralizes chyme • Regulation via • secretin from duodenal epithelial tissues • Cholecystokinin

32. Liver • Lobes divided into lobules • Blood from portal vein  sinusoids  central canal • Multiple functions • Blood glucose  glycogen  blood glucose • Lipid oxidation • Formation of urea from NH2 • Deamination of aa • Storage • Production of bile

34. Bile and the Gall Bladder • Bile • Bile salts • Others • Emulsification of lipids • Released as fatty substance enter lumen of duodenum • Cholecystokinin (CCK) stimulates contrations of gall bladder

36. Large Intestine • Regions • Cecum • Veriform appendix • Colon – 4 regions • Rectum • Anal canal • Internal & external anal sphincters • Functions

37. Symbiotic Bacteria Reside in the Colon • Numbers- about 50 species. • Fecal component- accounts for about 1/3 the total weight of feces. • They are nourished by undigested foods. • Their metabolic processes produce gas. • Some produce vitamins B and K. • They decompose pigmented molecules, which give feces its brown color.

39. Nutrition • Macronutrients – energy source • Calorie – measure of energy in foods • Micronutrients – required for vital biochemical processes • Incl. vitamins & minerals • Hydrolysis – initial step

40. Essential nutrients • Essential fatty acids • Required for synthesis of other forms in liver • Linoleic acid • Essential amino acids (8) • See table 15.8 • Complete vs partially complete proteins

41. Issues with Fats and Cholesterol • 4x amt of energy in carbs • Does Cholesterol intake greatly impact risk of heart disease? • What is the impact of intake of different kinds of fats on arthrosclerosis – (linked to heart disease)? • Trans fats?

44. Carbohydrates – all are not the same • Glycemic Index: impact/rate of change in blood glucose levels after ingestion

45. Some examples of high vs. low glycemic index foods • Impact of milling on glycemic index

46. Vitamins • Fat soluble • Water-soluble • B complex • C (ascorbic acid)

47. The End.