1.MUSCLES OF MASTICATION PRESENTED BY: Dr.DEEPAk(1ST YEAR)

2. CONTENTS INTRODUCTION DEFINITIONS MUSCLES OF MASTICATION CLINICAL CONSIDERATIONS OF MUSCLES REFERENCES 3. MASTICATION : Rhythmic opposition and separation of jaws with theinvolvement of teeth ,lips ,cheeks and tongue for chewingof food in order to prepare it for swallowing and digestion. Main purpose of mastication is to reduce the size of foodparticles to a size that is convenient for swallowing (bolusformation) with the help of saliva. 4. DEVEOPMENT OF MUSCLES OF MASTICATION The muscular system develops from intra embryonicmesoderm from embryonic cells called myoblast. Muscles of mastication are derived from first ormandibular arch (first arch). 5. LATERAL VIEW OF A FOUR WEEK EMBRYO SHOWINGMUSCLES DERIVED FROM BRANCHIAL ARCHES 6. MUSCLES OF MASTICATION 7. PRIMARY MUSCLES OF MASTICATION Masseter Temporalis Lateral pterygoid Medial pterigoid SECONDARY MUSCLES OF MASTICATIONThe suprahyoid group of muscles being used as secondary orsupplementary muscles they are Digastric Mylohyoid Geniohyoid 8. MASSETER Quadrilateral and consist of three layers. ATTACHMENTS Superficial Layer: : Origin- thick aponeurosis. From zygomatic process of maxilla and anterior 2/3 of lower border of zygomatic arch,pass downward and back wards at an angle of 45degree. Insertion - into lower part of lateral surface of ramus of mandible 9. MIDDLE LAYER Origin -anterior 2/3 of the deep surfaceand posterior 1/3 of the lower border ofthe zygomatic arch, Insertion - middle part of ramus. DEEP LAYER: Origin -deep surface of the zygomaticarch, Insertion - upper part of the ramus andinto the coronoid process. 10. RELATIONS OF MASSETERSUPERFICIAL Platysma Risorius Zygomaticus major Parotid gland Parotid duct Branches of facialnerve 11. DEEP SURFACE Overliesthe, Insertion of temporalisand ramus of themandible. In front buccinator andthe buccal nerve. Massetric nerve andartery. 12. ANTERIOR Margin projects over thebuccinator and is crossedbelow by the facial vein.POSTERIOR Margin is overlapped bythe parotid gland. 13. Nerve supply: Massetric nerve,branch of anterior divisionof mandibular nerve.Blood supply: Maxillary artery,which is a branch of externalcarotid artery. 14. ACTIONS OF MASSETERActions: Elevates the mandible to close themouth and to occlude the teeth inmastication. Its activity in the resting positionis minimal. It has a small effect in side-to-side movement, protraction andretraction. 15. TEMPORALIS MUSCLETEMPORAL FASCIAE Fan shaped Thick aponeurotic sheet that roofs over the temporalfossa and covers the temporalis muscle.. 16. ATTACHEMENTS Origin- whole of temporal fossa anddeep surface of temporal fascia Fibers converge and descend into atendon . It passes through the gap between thezygomatic arch and the side of theskull Insertion - Medial surface,apex,anterior andposterior border of coronoid processand anterior border of the ramus ofthe mandible as far as last molar 17. RELATIONS OF TEMPORALISSUPERFICIAL Skin Auricularis anterior Temporal fascia Superficial temporal vessels Auriculotemporal nerve Temporal branch of facial nerve Zygomatic arch masseter 18. DEEP SURFACE Temporal fossa Lateral pterygoid Superficial head of medialpterygoid Small part of buccinator Maxillary artery Deep temporal nerves Buccal vessels and nerveANTERIOR BORDER is seperated from the zygomatic bone by a mass of fat. 19. BLOOD SUPPLY Deep temporal part ofmaxillary arteryNERVE SUPPLY deep temporalbranches of theanterior trunk ofmandibular nerve. 20. ACTIONS OF TEMPORALIS Elevates the mandible, thismovement requires both the upwardpull of anterior fibers and backwardpull of the posterior fibers. Posterior fibers draw the mandiblebackwards after it has beenprotruded. It is also a contributory to side toside grinding movement. 21. SIDE TO SIDE GRINDING MOVEMENT 22. LATERAL PTERYGOID ATTACHMENTS It is a short thick muscle with two parts or head UPPER head arise from infratemporal surface and infratemporal crest of greater wing of sphenoid bone LOWER head arise from lateral surface of lateral pterygoid plate. Its fibers pass backwards and laterally to be inserted into a depression (pterygoid fovea)on the front of the neck of the mandible and into the articular capsule and disc of the temporomandibular articulation. 23. BLOOD SUPPLYPterygoid branch of2nd part of maxillaryarteryNERVE SUPPLYNerve to lateralpterigoid branchanterior division oftrigiminal nerve 24. ACTIONS OF LATERAL PTERYGOID Assists in opening the mouth with suprahyoid muscles. Right lateral pterygoid and right medial pterygoid turns the chin to left sideas a part of grinding movement. 25. When the medial and lateral pterygoids of two sides acttogether they protrude the mandible so that the lower incisorsproject in front of the other. The upper (superior) head being involved in chewing 26. The combinded efforts of the Digastrics and LateralPterygoids provide for natural jaw opening. 27. SIDE TO SIDE GRINDING MOVEMENT 28. Medial and lateral pterygoid act together toprotrude the mandible 29. MEDIAL PTERYGOIDIt is a thick quadrilateral muscleATTACHEMENTS Origin Superficial head (small): from the lateral surface of pyramidal process of thepalatine bone and tuberosity of maxilla Deep head (large): medial surface of lateral pterygoid plate and adjoiningprocess of the palatine bone. Its fibers pass downwards laterally and backwards Insertion -by a strong tendinous lamina ,to the postero-inferior part of themedial surfaces of the ramus and the angle of the mandible It is attached as high as mandibular foramen and as far forward as themylohyoid groove 30. RELATIONS OF MEDIALPTERYGOIDRELATIONS lateral pterygoid lateral pterygoid plate lingual nerve inferior alveolar nerve Ramus of mandible maxillary artery sphenomandibular ligament. 31. NERVE SUPPLY Branch of the maintrunk of themandibular nerve.BLOOD SUPPLY Pterygoid branch of2nd part of maxillaryartery 32. SECONDARY MUSCLES TAKING PART IN THE MASTICATION 33. The 4 primary muscles of mastication are in turn supported or supplemented by few secondary muscles known as SUPRAHYOID GROUP of muscles they are DIGASTRIC MYLOHYOID GENIOHYOID 34. DIAGASTRIC MUSCLE Two bellies united by tendon Origin Anterior belly from diagastric fossa of mandible. Posterior belly frommastoid notch of temporal bone. Insertion Both meet at the intermediate tendon and held by the fibrous pulley. The muscle has secondary role in mastication as a depressor muscle adding to theaction of lateral pterygoid muscle when mouth is to be opened against resistance.Elevation of hyoid bone 35. MYLOHYOID MUSLE Flat triangular Origin Mylohyoid line of mandible. Insertion Middle and Anterior fibers into median raphae. Posterior fibers body of hyoid bone. The secondary role of this muscle is evident as a depressor seenin action when mouth is to be opened against resistance. It elevates the floor of mouth to help in deglutition. 36. GENIOHYOID Short and narrow musle lies above mylohyoid Origin Inferior mental spine Insertion Anterior surface of body of hyoid bone. Geniohyoid elevates the hyoid bone and draws it forward,thus acting as a partial antagonist to stylohyoid. When the hyoid bone is fixed, it depresses the mandible 37. GENIOHYOID MUSCLE 38. IMPORTANT FACTS ABOUT MASTICATION There are about 15 chews in a series from the time of foodentry until swallowing Average jaw opening during chewing is between 16-20mm Average lateral displacement on chewing is between 3 and5mm Duration of masticatory cycle varies between 0.6and 1 sec Men chew faster and have a shorter occlusal phase thanwomen, it also depends on the type of food 39. Masticatory forces: The aver maximum sustainable biting force is756N{170 pounds}. Molar region: Biting force range 400-890N Premolar region: Biting force range 222-445N Cuspid region: Biting force range 133-334N Incisor region: Biting force range 89-111N {20-55 pounds} 40. CLINICAL CONSIDERATIONS 41. CLASSIFICATION OF DISEASES OF MUSCLEI PRIMARY MYOPATHIES Dystrophies Myotonias Hypotonias Myasthenias Myositis Metabolic defects Miscellaneous(amyloplasias,contractures,degeneration) 42. II.SECONDARY MYOPATHIESa)Atrophy1)Denervation2)Disuse and fixation3)Ageing and cachexiab) Hypertrophy1) Developmental2) Functionalc) Endocrined) Internal environment 1)Chemical 2)Vasculare)Infection1.Specific(toxoplasma,coxsackie virus, tetanus)2.General(rikettsial,typhoid,pneumococcal pneumonia)3.Post infection asthenia. 43. Muscle hypertrophy atrophy and hyperplasia HYPERTROPHY: when total mass of muscle enlarges.,increase in actin and myosin filament in response tomaximal force causing enlargement of muscle fiber. HYPERPLASIA: Under rare condition of extreme muscleforce generation actual number of muscle fiber have beenobserved to increase. ATROPHY: When total mass of muscle decreases. 44. MYASTHENIA GRAVIS Acquired autoimmune disorder of neuromuscular transmission characterized bymuscle weaknessETIOLOGY Antibodies to acetylcholine receptor on skeletal muscle fiberCLINICAL FEATURES Diplopia, ptosis, drooping of the face, And a very sorrowful appearance to thepatient. Patient rapidly exhausted, lose weight, death frequently occurs from respiratoryfailure. 45. TREATMENT AND PROGNOSIS Physostigmine administered intramuscularly improves thestrength of the affected muscle in a matter of minutes No cure is known even though the prognosis is good in therelapsing type. 46. TETANUS(LOCK JAW) Caused by exotoxins of gram positive bacillus Clostridium tetani. Disease of the nervous system characterized by intense activity of motor neuron and resulting in severe muscle spasm CLINICAL FEATURES Pain and stiffness in the jaws and neck muscles ,with muscle rigidity producing trismus and dysphagia Risus sardonicus Opisthotonous 47. TREATMENT All patients should receive antimicrobial drugs Active and passive immunization. Surgical wound care Anticonvulsant if indicated 48. BRUXISMBruxism : Jaw clenching, with or without forcible excursive movements,where the intensity of the clenching dictates the severity (or lack of)grinding .Clenching- It can occur as a brief rhythmic strong contractions of the jawmuscles during eccentric lateral jaw movements, or in maximumintercuspation,Causes 1) Associated with stressful events 2)Non stress related or hereditary 49. Bruxism may lead to-tooth wear-fracture of the teeth or restoratrion-uncosmetic muscle hypertrophy Treatment -coronoplasty -maxillary stabalization appliance 50. MYOFACIAL PAIN DYSFUNCTIONSYNDROME Pain Muscle tenderness Clicking in the joint Limitation in the mouth openingTREATMENT Reassurane Physiotherapy and Myotherapeutic exercises TENS (Transcutaneous Electronic Nerve Stimulation) Muscle relaxants surgery 51. Trismus during the administration of inferior alveolar nerveblock Irritation to the medial pterigoid muscle Musle pain occure due to space infection likepterygomandibular space infection. 52. 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