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Physiology Of GIT Mastication and Deglutition reflex.pptx
- 2. Learning objectives โข Define Mastication โข Explain the process of mastication reflex โข Discuss Deglutition and its reflex โข Define Peristalsis โข Role of lower esophageal sphincter
- 6. Ingestion of food โข Mastication โข Deglutition
- 7. Mastication โข First step in digestion of food Process involved in food preparation โข Chewing food- Role of teeth and muscles of jaw โข Mixing of food with saliva
- 8. Note movement of jaw
- 9. Role of teeth in mastication Chewing- mechanical breakdown of food โข Incisors โข Molars
- 11. All are supplied by trigeminal nerve
- 12. โข Mandibular division of 5th cranial nerve has nuclei in pons
- 13. Mastication reflex โข Rhythmical automatic movements โข Opening and closing of jaw
- 17. Significance of chewing โข Breaks food to smaller pieces โข More pieces๏ more surface for digestive enzymes โข Provides easiness for the food passage from stomach to small intestine
- 18. Deglutition โข Swallowing โข Passage of food from mouth to esophagus โข Mouth๏ Pharynx๏ Esophagus
- 19. 3 phases โข Oral โข Pharyngeal โข Esophageal
- 20. Oral phase โข Voluntary phase โข Food is prepared for swallowing โข Tongue plays major role โข Food is rolled posteriorly into pharynx
- 22. Pharyngeal phase โข Involuntary โข Soft palate moves upward โข Epiglottis moves backward โข Vocal cord approximates
- 24. Upper esophageal sphincter muscles relaxes
- 25. โข Bolus of food is moved to esophagus via constriction of pharyngeal constrictor muscles
- 28. Esophageal stage of swallowing โข Passage of food from Pharynx to Stomach
- 30. Peristalsis
- 32. โข 2 types of peristalsis 1. Primary peristalsis 2. Secondary peristalsis
- 33. Pharyngeal muscles are striated
- 34. Esophagus muscles โข Superior 1/3rd striated skeletal โข Inferior 2/3rd non striated smooth
- 37. Receptive relaxation of stomach โข Stomach relaxes to receive food from esophagus โข Wave of peristalsis is preceded by wave of inhibition
- 40. Role of lower esophageal sphincter โข Helps prevent reflux of stomach acid into esophagus
- 42. Neurogenic control of swallowing
- 44. Disorders of swallowing โข Dysphagia โข Achalasia
- 45. Dysphagia โข Difficulty in swallowing โข Damage to nerve (V, IX and X) โข Damage to swallowing center
- 46. Diseases that affect swallowing โข Poliomyelitis โข Encephalitis โข Mysthenia gravis โข Botulinism
- 48. Achalasia
- 51. โข Loss of inhibitory neurons in myenteric plexus
- 52. โข Esophageal stasis leads to infection of esophagus
Editor's Notes
- The nociceptive, or flexor, reflex is a polysynaptic reflex to noxious stimuli and is therefore considered to be protective. Examples in the large limbs include the withdrawal of a hand as it touches a hot object. In the masticatory system, this reflex becomes active when a hard object is suddenly encountered during masticationโfor example when, in eating a cherry pie, you unexpectedly encounter a cherry pit (Figure 2-7). The suddenly increased chewing force placed on the tooth instantly overloads the periodontal structures, producing a noxious stimulus. The primary afferent nerve fibers carry this information to the trigeminal spinal tract nucleus, where they synapse with interneurons. These interneurons travel to the trigeminal motor nucleus. The motor response that occurs during this reflex is more complicated than the myotatic reflex in that the activity of several muscle groups must be coordinated to carry out the desired motor response.9,10 Not only must the elevator muscles be inhibited to prevent further jaw closure on the hard object but the jaw opening muscles must be activated to bring the teeth away from potential damage.11,12 As the afferent information from the sensory receptors reaches the interneurons, two distinct actions occur. Excitatory interneurons leading to the efferent neurons in the trigeminal motor nucleus of the jaw-opening muscles are stimulated. This action causes these muscles to contract. At the same time, the afferent fibers stimulate inhibitory interneurons, which causes the jaw-elevating muscles to relax. The overall result is that the jaw quickly drops and the teeth are pulled away from the object causing the noxious stimulus. This process, called antagonistic inhibition, occurs in many nociceptive reflex actions throughout the body.