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Physiology Of GIT Mastication and Deglutition reflex.pptx
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- 2. Learning objectives ⢠DefineMastication ⢠Explain the process of mastication reflex ⢠Discuss Deglutition and its reflex ⢠Define Peristalsis ⢠Role of lower esophageal sphincter
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- 6. Ingestion of food â˘Mastication ⢠Deglutition
- 7. Mastication ⢠First stepin digestion of food Process involved in food preparation ⢠Chewing food- Role of teeth and muscles of jaw ⢠Mixing of food with saliva
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- 9. Role of teethin mastication Chewing- mechanical breakdown of food ⢠Incisors ⢠Molars
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- 11. All are suppliedby trigeminal nerve
- 12. ⢠Mandibular divisionof 5th cranial nerve has nuclei in pons
- 13. Mastication reflex ⢠Rhythmicalautomatic movements ⢠Opening and closing of jaw
- 17. Significance of chewing â˘Breaks food to smaller pieces ⢠More piecesď more surface for digestive enzymes ⢠Provides easiness for the food passage from stomach to small intestine
- 18. Deglutition ⢠Swallowing ⢠Passageof food from mouth to esophagus ⢠Mouthď Pharynxď Esophagus
- 19. 3 phases ⢠Oral â˘Pharyngeal ⢠Esophageal
- 20. Oral phase ⢠Voluntaryphase ⢠Food is prepared for swallowing ⢠Tongue plays major role ⢠Food is rolled posteriorly into pharynx
- 22. Pharyngeal phase ⢠Involuntary â˘Soft palate moves upward ⢠Epiglottis moves backward ⢠Vocal cord approximates
- 24. Upper esophageal sphinctermuscles relaxes
- 25. ⢠Bolus offood is moved to esophagus via constriction of pharyngeal constrictor muscles
- 28. Esophageal stage ofswallowing ⢠Passage of food from Pharynx to Stomach
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- 32. ⢠2 typesof peristalsis 1. Primary peristalsis 2. Secondary peristalsis
- 33. Pharyngeal muscles arestriated
- 34. Esophagus muscles ⢠Superior1/3rd striated skeletal ⢠Inferior 2/3rd non striated smooth
- 37. Receptive relaxation ofstomach ⢠Stomach relaxes to receive food from esophagus ⢠Wave of peristalsis is preceded by wave of inhibition
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- 40. Role of loweresophageal sphincter ⢠Helps prevent reflux of stomach acid into esophagus
- 42. Neurogenic control ofswallowing
- 44. Disorders of swallowing â˘Dysphagia ⢠Achalasia
- 45. Dysphagia ⢠Difficulty inswallowing ⢠Damage to nerve (V, IX and X) ⢠Damage to swallowing center
- 46. Diseases that affectswallowing ⢠Poliomyelitis ⢠Encephalitis ⢠Mysthenia gravis ⢠Botulinism
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- 51. ⢠Loss ofinhibitory neurons in myenteric plexus
- 52. ⢠Esophageal stasisleads to infection of esophagus
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Editor's Notes
- #15Â 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 masticationâfor 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.