DIGESTIVE SYSTEM

1. DIGESTIVE SYSTEM drg. ANIS A. MAKKY, MKes ORAL BIOLOGY DEPARTEMENT AIRLANGGA UNIVERSITY SURABAYA, APRIL 16, 2007

2. FUNCTION 1. ingest food 2. break food down physically and chemically into absorbable nutrient molecule 3. absorb those molecules into the bloodstream 4. eliminate any indigestible remains.

3. 2 MAJOR GROUPS OF ORGANS IN THE DIGESTIVE SYSTEM • ALIMENTARY CANAL : • organs thrue which food actually passes • ACCESSORY ORGANS : • they assist in digestion, but no food actually • passes through them

4. ALIMENTARY CANAL * oral cavity * esophagus * pharynx * stomach * small intestine * large intestine. ACCESSORY ORGANS * teeth * tongue * salivary glands * pancreas * liver * gallbladder.

6. THE DIGESTIVE SYSTEM PERFORMS 6 BASIC ACTIVITIES: • Ingestion • Propulsion • Mechanical Digestion • Chemical Digestion • Absorption • Defecation

10. ORAL CAVITY STRUCTURES 1. deciduous teeth (20)     2. permanent teeth (32)     3. tongue        a. skeletal muscles        b. moves food mass “bolus”        c. appropriate use of “lingual” terminology

11. ORAL CAVITY STRUCTURES 4. major salivary glands (3 pair)        a. parotid - masseter - mumps      b. submandibular - medial aspect of the mandibular body - duct : lingual frenulum       c. sublingual - anterior submandibular gland & under the tongue - its 10-12 ducts : floor of the mouth.

12. ORAL CAVITY STRUCTURES     5. minor salivary glands * lingual glands (on the tongue) * buccal & labial glands (in the cheek & lip) * palatine glands (in the palate) * glossopalatine glands (on the glossopalatine fold)    

14. SALIVA • contains : enzymatic & nonenzymatic protein • calcium • phosphorus • sodium • other salt • dissolve gasses : N2, O2, CO2 • cells (leukocytes : ginggival sulcus) • saliva is 99% water

15. pH : depends on the rate of secretion • faster : more alkaline (meal) • sleep : low • resting : 5, 81 (parotid gland) • 6,39 (submandibular gland) • average : 6,7 • secretion : follow diurnal rhytms • total volume : 600 – 700 ml up to 1500 ml

16. secretion parotid gland : 60-65% • submandibular : 20-30% • sublingual : 2-5% • minor gland : 6-7% • sulcus gingival : 10-100 µl/h

17. Function of the saliva • digestive • antibacterial • lubrication • taste • buffering action • hygienic action • blood coagulation & tissue repair • inhibition of dental caries • water balance

18. Control of saliva secretion • taste • smell • mechanical stimulation • mechanical irritation • mastication of the food • chemical irritation • distention or irritation of the oesophagus • chemical irritation of the stomach • pregnancy

20. PHARYNX 1. oropharynx     2. esophagus : connects pharynx to stomach     3. peristalsis - rhythmic smooth muscle contractions propel material inside

21. LAYER of DIGESTIVE ORGAN • mucosa • submucosa • muscularis • serosa

23. MUCOSA • functions : • protecting against pathogens; absorbing nutrients; • and secreting mucus, enzymes, hormones • the mucosa consists of 3 sublayers: • * epithelium : hormone, enzyme, goblet cell • * lamina propria : blood vessels, lymph vessels, • and lymph nodules • * muscularis mucosae : • local movements of the mucosa

25. submucosa : • * contains : • ** blood vessels, lymphatic vessels • ** lymphatic nodules • ** nerve fibers : • submucosal plexus • = Meissner plexus

26. muscularis externa : • * 2 layers of smooth muscle : • circular & longitudinal • * between 2 layers : • myenteric plexus = Auerbach plexus • * functions : segmentation & peristalsis • * in several places : • the circular layer thickens to form sphincters

27. Serosa : • most exterior layer

28. MUSCLE of GIT : most smooth m. 2 types : 1. multi unit smooth m. 2. visceral smooth m. • Smooth m. consist of : • actin • dense bodies : actin + actin • myosin

31. SMOOTH MUSCLE POTENTIAL • Slow waves : rhytmic, not action potential, resting • freq. 3-12 per minutes • gaster  3/min. • duodenum  12/min. • ileum  8-9/min. • cause  ? • “ sodium-potasium pump”

32. SMOOTH MUSCLE POTENTIAL 2. Spike potential : true action potential occurs automatically firing level : -40 mvolt RMP : 50-60 mvolt stimulation : stretch, asetilkolin, parasympathetic

34. SMOOTH MUSCLE CONTRACTION

36. ESOPHAGUS • regulated by : • cardiac or gastroesophageal sphincter • collapsed when : empty • upper 1/3 is skeletal • middle 1/3 a mixture • lower 1/3 smooth

37. STOMACH • its functions include : • * storage of food • * chemical and mechanical digestion • bolus  chyme (paste) • it is found nearly hidden by the liver • when it is empty : its J-shaped • and collapsed : folds  known as rugae

38.  general anatomic regions     a. cardia    b. fundus    c. body    d. pyloric region • it is important in the process of physical digest • gastric pits • pyloric sphincter regulates • entry into the duodenum

40. gastric pits  4 major secretory cells:        a. chief cells        b. parietal cells        c. G-cell        d. mucus cell

41. chief cells : pepsinogen* activation : by low pH to form pepsin* pepsin is a protease for protein digestion • b. parietal cells i. HCl   * secretion enhanced by histamine via H2 recep.    * tagamet blocks H2 histamine receptors to • inhibit HCl secretion ii. intrinsic factor    binds to and allows B12 absorption in intestines     

42. c. G-cell : gastrin hormone    * activates gastric juice secretion & gastric smooth muscle “churning”     * activates gastroileal reflex which moves chyme from ileum to colon d. mucus cell :    protective role of mucus against acids and digestive enzymes

44. What prevents the proteolytic enzymes and HCl secreted by the stomach from damaging itself? • There are 3 basic reasons : • a thick coat of alkaline mucus coats the • stomach walls • mucosal epithelial cells are joined by tight • junctions and are impermeable to HCl • damaged epithelial cells are quickly shed and • replaced