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Gastroinstestinal System Lecture 1

Physiology II. Gastroinstestinal System Lecture 1. Dr Than Kyaw 23 May 2012. Introduction. Gastroinstestinal System (Alimentary system, Digestive system). Living things – the most important = to live Need to – eat food – digest it

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Gastroinstestinal System Lecture 1

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  1. Physiology II Gastroinstestinal SystemLecture 1 Dr Than Kyaw 23 May 2012

  2. Introduction Gastroinstestinal System (Alimentary system, Digestive system) • Living things – the most important = to live • Need to – eat food – digest it – use digested materials for body building, maintenance, production • Without food – survive for a few days/month – use body stores and tissues

  3. Introduction • Know the order of principle parts of Alimentary (GI) tract • Carnivorous – flesh eating • Herbivorous – plant eating • Omnivorous – eat both flesh and plants • Digestive systems develop differently in different spp. e.g. Cecum of horse (large) but of dog (very small) (why?) - functional need/amount of fermentation required

  4. Functional Anatomy of GI Tract 1. Oral cavity (Mouth)TeethTonguePharynx2. StomachEsophagusSimple & compound stomach3. Intestines Small Large4. Accessory organs Salivary glands Pancreas Liver

  5. Oral cavity - Most cranial part- Food is first received- Teeth and tongue - assist digestionTeeth- cutting- reduce the size of ingested food particles by grinding- increase surface areas – chemical + microbiologic degradation

  6. Types of teeth • Incisors (nippers): most forward teeth; for cutting • Canine teeth (tasks, fangs, eye teeth) - tearing and separation of food • Premolars - caudal to the canines - grinding • Molars - grinding • Premolars & molars = cheek teeth

  7. TEETH (INCISORS) Carnivore Short and pointed Herbivore Broad, flattened and spade shaped Omnivore Short and pointed Human Broad, flattened and spade shaped

  8. TEETH (CANINES) Carnivore Long, sharp and curved Herbivore Dull and short or long, or none Omnivore Long, sharp and curved Human Short and blunt

  9. TEETH (MOLARS) Carnivore Sharp, jagged and blade shaped Herbivore Flattened with cusps, complex surface Omnivore Sharp blades and/or flattened Human Flattened with nodular cusps

  10. Dental formulas Dental formulas: domestic animals (permanent teeth) • One side of the jaw • Numerator = upper jaw • Denominator = lower jaw Cow* Horse *Note: Cow, sheep and goats have no upper incisors; but a dental pad

  11. (C) Sheep (D) Pig (E) Dog

  12. - Upper cheek teeth – slightly wider apart than lower arcade – also has wider table (grinding surface) than lower teeth - In horse - uneven wear (hooks) - points are formed - cause injury to the bucal or lingual membranes - painful, unable to eat - filing off the points with a dental rasp (floating of the teeth)

  13. Horse: formation of points Reece (2009)

  14. Eruption of teeth and age • Age of animal estimated by the stage of eruption • E.g: cow (permanent teeth eruption) • Search and observe dentition for other animals • Muscles related to chewing

  15. Tongue Muscular organ - longitudinal - Circular - transverse Extremely mobile

  16. What does a tongue can do? - Maneuver food mass - seize - bring into the mouth - move food to the table surfaces of teeth - swallowing - gustation (taste) - clean the fur and body - remove oil and parasites - catching the prey - heat regulation

  17. Taste buds on the tongue • Numerous projections – k/s papillae - for traction of food - grooming of the offspring • Types of Papillae - Vallate: Large circular projections surrounded by a deep groove - Fungiform: like tiny mushroom - Filliform: pointed projection - Folliate: like leaf - Conical: cone shaped

  18. Nerve supply - Facial nerve (VII) - Glossopharyngeal nerve (XI)

  19. Taste buds - Chemical senses - Important for feed intake of man and animals • Abundant in - Vallate, folliate and fungiform papillae - Soft palate - Parts of pharynx - Epiglottis - Larynx

  20. Taste Buds, Taste Receptor Cells, and Taste Nerves The sense of taste - mediated by taste receptor cells which are bundled in clusters called taste buds. Taste receptor cells sample oral concentrations of a large number of small molecules and report a sensation of taste to centers in the brainstem.

  21. Number of taste buds Cattle – 25000 Pig - 15000 Cat - 470 Chicken – 30 Goat - 15000 Man - 8,000 - 10,000 Catfish - 100,000 – 175,000

  22. Pharynx • Common passage to air and food - Naso-pharynx - Oro-pharynx - Laryngo-pharynx • Responsible for the proper directing of - air to the air passage - food and liquid to the esophagus

  23. Mastication and Deglutition(Chewing and swallowing) • Mechanical breakdown of food (chewing) • Fibrous food – require more chewing • Bolus (round/oval) mixed with saliva - mucus: adhesion & lubrication for ease of swallowing

  24. Swallowing (deglutition) - co-ordinated with swallowing center in the brain • Mouth – voluntary initiation • Pharynx – reflex action • Esophagus - reflex • Unconsciousness – danger of inhaling vomitus due to – lack of voluntary control - depressed reflex centers

  25. Swallowing (deglutition) The sequences of reflexes: • Respiration inhibited (danger of inhaling food minimized) • Glottis (opening to larynx) closed • Larynx - pulled upward and forward • Root of tongue – fold the epiglottis over the glottis as the tongue plunges the bolus from mouth to pharynx • Soft palate – elevated; close the nasal cavity from pharynx • Peristaltic contraction of pharynx – directs food from pharynx to esophagus • Reflex peristaltic wave – initiated, transport bolus to stomach

  26. Salivary glands and saliva • Parotid - Serous (watery, clear fluid) • Sublingual - Mucous (viscid, tenacious and protective) • Mandibular - mixed (serous and mucous) 3 paired, well defined salivary glands Autonomic nerve supply (symp- and parasymp)

  27. Salivary glands of dog Zygomatic Parotid Mandibular Sublingual Duct of sublingual gland

  28. Salivary glands of horse 1 Submaxillary gland. - - Submaxillary duet (Wharton's duct). 3 Cluster of openings of ducts of sublingual glands. 4 Tongue. 5 Circumvallate papilla. 6 Fungiform papillae. 7 Jugular vein. 8 Submaxillary vein. • 1 Parotid gland. 2 Molar glands. 3 Sublingual gland. 4 Parotid Duct. 5 Massetermuscle. 6 Facialnerve. 7 Jugular vein. 8 Submaxillary vein. 10 Labial glands. 11 Labial ducts.

  29. Salivary glands and saliva Saliva contains: water Electrolytes Mucus and Enzymes – amylase (present in pig; absent in ruminants and dog) Amount of saliva - greatest in herbivores - 80% of water entering the stomach in cattle is provided by saliva

  30. Salivary glands and saliva

  31. Salivary glands and saliva Function of saliva • buffering action in ruminants (neutralize acids produced by fermentation) pH 6.2 – 6.8 • Digestion of carbohydrate by amylase • evaporation and cooling in panting animals

  32. Esophagus • Muscular tube – from pharynx to stomach through thoracic cavity, diaphragm • Constriction waves of muscular contractions (peristaltic movement)

  33. Peristalsis • both longitudinal and circular muscle fibers propel the ingesta, consisting of a wave of contraction passing along the tube. • Increased peristalsis means faster movement of ingesta through the gut and less absorption of fluid, both tending to diarrhea. • Reduced peristalsis means a longer alimentary sojourn, greater inspiration of ingesta and a tendency to constipation.

  34. Circular muscle contraction Bolus Circular muscle relaxation

  35. Antiperistalsis / Reverse peristalsis • peristalsis directed orally (reverse of going to stomach) • Result of intestinal obstruction and acute, significant distention of the intestinal lumen • May also rise from mild digestive upsets • Major contributing mechanism in vomiting.

  36. Vomition (Emesis) • forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose • Protective response to remove potentially harmful ingesta from the stomach and upper small intestine • Relaxation of upper and lower esophageal sphincters, glottis, nasal cavity • Reflex action through vomiting center in the brain

  37. Regurgitation vs. vomiting • Rregurgitation: • - passive expulsion of ingested material out of the mouth • - normal component of ruminant digestion for cud chewing • - Cattle and horses vomit rarely • - Dogs and cats vomit easily and frequently,

  38. Stomach • Simple stomach • Complex stomach

  39. E C F B P ? E = Esophagus C = Cardia F = Fundus B = Body P = Pylorus

  40. Simple stomach and digestion • Dilated portion • Store ingesta temporarily • Contract and mix food with gastric juice Chyme Gastric juice Water Mucus HCL Pepsinogen renin Gastric glands in regions of Cardia Fundus pylorus

  41. Simple stomach Regulation of gastric secretion Intestinal phase (inhibitory) Cephalic phase(stimulatory) Gastric phase (stimulatory) Smell, Sight, taste, Thinking of food Cholecystokinin and secretin (hormones released by duodenum) Presence of food in the stomach (stretch) • Pyloric gland (G cells) • Parietal cells • Chief (peptic) cells • Gastrin (hormone) • HCL • Pepsinogen (proteolytic enzyme)

  42. Simple stomach Cephalic phase Smell, Seeing, taste Thinking of food Parasympathetic (vagal) sti medulla oblongata endocrine cells in the stomach Gastrin secretes gastric juice stomach circulatomrysystem

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