Masticating apparatus


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It contains following subheadings:
-maxilla and mandible anatomy
-TMJ(Temporo mandibular joint)
-Muscles of mastication

Dr. Syed Irfan Qadeer
Prof. and HOD Department of Anatomy

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  • Masticating apparatus

    1. 1. The Mastication Apparatus
    2. 2. Mastication Apparatus • The Mastication apparatus consist of a centre core or a framework consisting of the bones, the temporomandibular joint and the muscles of mastication.
    3. 3. Maxilla • It is the second largest bone of the face • It forms the upper jaw with the fellow of the opposite side • It also contributes to the formation of 1. Floor of the nose and the orbit 2. Roof of the mouth 3. Lateral wall of the nose 4. Pterigopalatine and infratemporal fossae 5. Pterigomaxillary and infraorbital fissures
    4. 4. Anatomy of the maxilla • The anatomy of the maxilla has two main parts: 1. Body(pyramidal shape) – Anterior surface – Posterior surface – Orbital surface – Nasal surface 2. Processes – Zygomatic – Frontal – Alveolar – Palatine
    5. 5. Anterior Surface: • Incisive Fossa: – Depressor septi nasi – Orbicularis oris • Canine fossa: – Levator anguli oris • Infraorbital foramen (above canine fossa) – Infraorbital nerves and vessels • Above sharp border between anterior and orbital surface: – Levator labi superioris • Nasal notch: Dilator Naris • Ant Nasal Spine
    6. 6. Posterior Surface • It is directed backwards and laterally • It forms anterior wall of the infratemporal fossa • Anterior and posterior surfaces are seperated by ridge which leads to the socket of 1st molar tooth • Near the centre of posterior surface 2 to 3 openings of dental canal for posterior superior alveolar vessels and nerves • At the lower end there is a raised maxillary tubrosity which is rough in the upper part of its medial end for tubercle of the palatine bone which has the attachment of superficial fibres of themedial pterigoid muscles • Above this smooth surface which forms the boundry of the ptrigopalatine fossa is grooved for the maxillary nerve, this groove is contineous with the infra orbital groove
    7. 7. Orbital surface Smooth and triangular • Medial border – Notch: lacrimal notch – Behind this it articulates with the • Lacrimal • Orbital plate of ethmoid • Orbital process of palatine • Posterior border: Smooth, rounded and it forms greater part of infraorbital fissure in middle infraorbital groove • Anterior border: forms orbital margin ,infraorbital groove and canal; a little lateral to this is canalis sinuosus which passes in the anterior wall of the maxillary sinus and reaches in the nasal cavity and opens in the side of the nasal septum in front of incisive canal • A little lateral to the lacrimal groove there is attachment of inferior oblique muscle of eveball
    8. 8. Nasal Surface • In its upper posterior part there is a large maxillary hiatus which leads into the maxillary sinus In articulated skull this hiatus is completed by ethmoid and lacrimal bones • Behind this there is a rough impression for the perpendicular plate of palatine bone • Infront of maxillary hiatus there is a lacrimal groove • More anteriorly concal crest for articulation with inferior nasal concha
    9. 9. Maxillary Sinus • Large pyramidal cavity with its apex directed laterally towards the zygomatic process • Base is towards the lateral wall of the nose • In articulated skull it is reduced by Above • Uncinate process of ethmoid • Desending part of lacrimal bone Below: inferior nasal concha Behind: perpendicular plate of palatine • It opens into the middle meatus of the nose usually by two openings one of which is closed by mucous membrane in living state • Occasionally there are projections in the maxillary sinus from roof to anterior wall
    10. 10. Processes • Zygomatic: it is rough and pyramidal – Front:it is contineous with the anterior surface of body – Behind(concave):in continuity of the posterior surface – Above: articulates with zygomatic bone – Below(arched border) which anterior and posterior surface of the body
    11. 11. • Frontal Process: – Lateral Surface: • Vertical ridge (Lacrimal crest) • Groove for the lacrimal sac – Medial surface: It is rough and uneven and articulates with the ethmoid and also closes the anterior ethmoidal sinus below ethmoidal crest • Upper end: Articulates with the frontal bone • Anterior border with the nasal bone • Posterior border with the lacrimal bone
    12. 12. • Alveolar processes: It has thick arched border behind and contains sockets to receive roots of teeth which vary in size and depth – Canine deepest – Molar widest and subdivided into 3 minor sockets by septae – Incisors and premolars single – Occasionally incisors are divided into 2 sockes
    13. 13. • Palatine Process: Thick strong horizontal – Inferior surface is concave and presents numerous foramina for passage of nutrient vessels and contains depressions for lodgement of glands – Groove for grater palatine Vessels and nerves – Incisive fossa leads into the incisive canal – Sometimes anterior and posterior incisive foramen for long sphenopalatine nerve which communicates with the greater palatine nerve – Upper surface: forms the floor of the nasal cavity – Lateral Border fuses with rest of the bone – Posterior border fuses with the horizontal plate of the palatine
    14. 14. Muscles attached to maxilla
    15. 15. Muscles of face
    16. 16. Arterial supply
    17. 17. Maxillary Artery
    18. 18. Veinous drainage
    19. 19. Nerve Supply
    20. 20. Lymphatics
    21. 21. Age changes in Maxilla
    22. 22. Mandible • Largest and strongest bone of the face • Curved horizontal body; convex forwards • It has two rami which project upward from posterior end of the body • The body is horse shoe shaped
    23. 23. External Surface • Faint ridge: symphisis menti • Mental protuberance in the triangular area below sympisis menti • Mental tubercle on each side of mental protruberance • Mental foramen between premolar teeth • Oblique line
    24. 24. Internal Surface • Myelohyoid line • Sub mandibular fossa • Sub lingual fossa • Genial tubercle • Myelohyoid groove
    25. 25. Borders • Upper boder: – Sockets for the mandibular teeth are present • Lower border(Base) presents a digastric fossa • Ramus – Lateral Surface – Medial Surface • Mandibular foramen canal • Lingula- mylohyoid groove • Inferior border is continuous with the angle of mandible • Upper Border: Mandibular Notch
    26. 26. Arterial Supply of Maxilla and Mandible
    27. 27. Nerve supply of Mandible
    28. 28. Veinous drainage of Mandible
    29. 29. • Processes: – Condylar – Coronoid • Mandibular canal
    30. 30. Age changes in mandible
    31. 31. Applied Anatomy Muscle injuries: Its cause and effects • Incisivus labii Superioris: – During the exposure of the bone of premaxilla between the canines ,a mucoperiosteal flap reflection may detach the muscle and if the muscle gets damaged the the drooping of the septum and ala of the nose may occur
    32. 32. • Mylohyoid muscle – Surgical manupulation of the floor of the mouth may result in edematous swelling of the sublingual space (above the mylohyoid muscle )and submandibular space(below the mylohyoid muscle) – Cellulitis of this sublingual space in quiet common however excessive bilateral cellulitis of the sublingual spaces may push the tongue backwards and compress the pharynx and may result in airway obstruction
    33. 33. • Genoiglossus muscle – During the elevationof the lingual mucosa before making an impression for a subperiosteal implant a portion of the muscle may be reflected from te genial tubercle, however if the muscle is completly detached from the tubercle it may lead to retrusion of the tongue and airway obstruction
    34. 34. • Medial pterigoid – The medial pterigoid muscle binds the pterigomandibular space medially ,during surgical procedures involving the area of pterigomandibular space infection may occour and may be dangerous due to its closed proximity to the pharyngeal space – Surgical exposure of the tissue posterior to the maxillary tubrosity may also involve the medial pterigoid muscle as a part of the muscle originates from the maxillary tubrosity
    35. 35. • Lateral pterigoid muscle – The lateral pterigoid muscle fibres are placed in an angulated manner and because of this there may be pain in patients with a full arched subperiosteal implant or prosthetic splint
    36. 36. • Mentalis muscle: – Complete reflection of the mentalis muscle for the purpose of extension of a subperiosteal implant may result in a condition known as witch’s chin There is failure of the mentalis muscle reattachment following the implantation. An external bandage is applied for four days to help in the reattachment of the muscle
    37. 37. • Buccinator muscle: – Myositis of the detached buccinator muscle in patients with subperiosteal implants may cause swelling and pain at the site of origin of the muscle
    38. 38. Nerve injuries • Inferior alveolar nerve: – The nerve may be damaged easily when making an incision or reflection of the mucosa in its area therefore position of the inferior dental canal in vertical and buccolingual dimension is of great importance during site preprations for implants
    39. 39. • Lingual nerve – The position of the nerve is lateral to the retromolar pad the incision should remain lateral to the pad and the mucosal reflection should be done with a periosteal elevator in constant contact with the bone to prevent injury to the nerve
    40. 40. • Nerve to mylohyoid: – The nerve lies in closed relation to the ramus of mandible hence it is prone to get damaged during surgical intervention
    41. 41. • Long buccal nerve: – When the ramus is accessed for the purpose of a block graft excision great care must be take to protect this nerve from injury
    42. 42. Injury to vessels • Maxillary vessels: – During the surgical orthognathic procedures the major nutrient artery of the maxilla are sometimes damaged, but the blood supply is maintained by anastamosis present in the soft palate
    43. 43. The Temporomandibular joints • It is a joint present between head of mandible and the articular fossa and articular eminance of the temporal bone Type of joint: It is a condylar variety of synovial joint The joint cavity of TMJ is divided by fibro- cartilagenous disc into 2 compartments
    44. 44. Bony framework of joint • Proximal : Articular fossa and the articular eminance of the mandible • Distal side: Head of mandible Articular surfaces: • The anterior eminance is formed by the root of zygoma and the articular surface is formed by the smooth area of tht mandibular fossa of the temporal bone • The distal articular surface is also a smootharea forned by the head of the mandible.
    45. 45. The ligaments of TMJ • True ligament – Capsular ligament – Temporomandibular ligament • Accessory ligament – Stylomandibular ligament – Sphenomandibular ligament
    46. 46. True ligaments • Capsular ligament: It is like a fibrous sac over the joint cavity. It is attached above to the articular surface of TMJ and on the other side to the neck of the mandible – It covers the joint cavity very loosely – It is covered by the synovial membrane
    47. 47. • Temporomandibular ligament: – this ligament is the thickening of the lateral part of the capsular ligament – It runs posterio-inferiorly and is attached above to the articular surface and below to the ramus of mandible and the posterio-lateral aspect of the mandible
    48. 48. Accessory ligament It provides additional support to the TMJ • Stylomandibular ligament: This ligament is formed by the thickening of the deep cervical fascia. – It is attached above to the styloid process and below to the angle of mandible and lateral border of ramus of mandible – This ligament helps to seperate the parotid gland and the submandibular gland
    49. 49. • Spheno-mandibular ligament; This ligament is attached above to the spine of the sphenoid bone and below to the lingula on the mandible. – This ligament is innervated by various nerves and vessels – Embryologically it is the un-ossified intermediate part of the Meckel’s cartilage of the 1st branchial arch
    50. 50. Interior of the joint • The bones forming the joint cavity are covered by fibrous cartilage rather than the hyaline cartilage • The absence of hyaline cartilage makes it an atypical type of synovial joint
    51. 51. The articular disc • The articular disc divides the joint into two compartments, the upper and the lower compartment • Articular disc is a fibro-cartilagenous disc, it is thickened in the periphery and thin in the center • The vascularity is also more in the periphery
    52. 52. Relations of the joint • Anteriorly: fibres of the muscles of lateral pterigoid • Posteriorly: part of the parotid gland • Medially: spheno mandibular ligament • Laterally: parotid gland
    53. 53. Development of TMJ • Temporomandibular ligament developes from the mesenchyme situated between the developing temporal bone above and the mandibular condyl below • During 12 weeks of development two clefts appear and remain separated from each other by an intervening mesenchymal plate – These clefts become the upper and the lower joint cavities – The mesenchymal plate becomes the articular disc – Condensation of the mesenchyme around the developing joint becomes the capsule of the joint
    54. 54. The supply of the gland • Arterial supply • Superficial temporal artery • Maxillary artery • Veinous drainage • Superficial temporal vein • Retromandibular vein • Lymphatics: It drains into the superficial and deep parotid lymph nodes and deep cervical nodes.
    55. 55. Movements of the TMJ • The principle movements of the joint are: » Elevation » Depression » Protraction » Retraction » Side to side movements Various muscles are involved in these movements, collectively known as muscles of mastication.
    56. 56. Elevation •Messeter •Anterior fibres of temporalis •Medial Pterigoid Depression •Lateral pterigoid muscle •Anterior belly of digastric, mylohyoid and geniohyoid also assist Protraction Retraction •Masseter, Medial pterigoid and lateral pterigoid •Deep fibres of masseter •Posterior fibres of temporalis Side to side movements •It is caused by alternate contraction and relaxation of Medial and lateral pterigoid
    57. 57. Muscles of mastication • There are 4 muslces involved in mastication – Masseter – Temporalis – Medial pterigoid – Lateral pterigoid
    58. 58. Masseter • Origin: it arises from 2 heads • Superficial hear arises from the lower border of the anterior 2/3rd of the zygomatic arch • Deep head arises from the whol length of the zygomatic arch and lower border of th posterior 1/3rd of the zygomatic arch. • Insertion: The two heads unite and gets inserted into the whole length of the outer surface of the ramus and angle of mandible • N. Supply: Massetric nerve and a branch of anterior division of the Mandibular nerve • Actions: • Elevation of mandible • Protrusion of the mandible
    59. 59. Temporalis • Origin: whole length of the temporal fossa, the fascia covering of the temporalis and from the inferior temporal line The anterior fibres are vertical, posterior are horizontal and middle fibres are oblique • Insertion: all the fibres converge to form a thick tendon which passes deep to the zygomatic arch and is inserted into the medial surface, the apex, the anterior and the posterior border of the coronoid process and anterior border of ramus of mandible upto the last molar tooth. • Nerve supply: Deep temporal nerve which arises from the anterior division of the mandibular nerve • Actions: Anterior fibres are strong elevators of the mandible Posterior fibres retract the mandible
    60. 60. Lateral Pterigoid • Origin: It also arises from two heads – The upper/superior head originates on the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone, – lower/inferior head on the lateral surface of the lateral pterigoid plate • Insertion: Inferior head inserts onto the neck of condyloid process of the mandible; upper/superior head inserts onto the articular disc and fibrous capsule of the temporomandibular joint • N. Supply: The mandibular branch of the fifth cranial nerve, the trigeminal nerve, specifically the lateral pterigoid nerve, innervates the lateral pterygoid muscle. • Actions: Unlike the other three muscles of mastication, the lateral pterygoid is the only muscle of mastication that assists in depressing the mandible (opening the jaw).
    61. 61. Superior head of lateral pterigoid Inferior head of lateral pterigoid
    62. 62. Medial pterigoid • Origin: – The bulk of the muscle arises as a deep head from just above the medial surface of the lateral pterigoid plate. – The smaller, superficial head originates from the maxillary tuberosity and the pyramidal process of the palatine bone. • Insertion: Its fibers pass downward, lateral, and posterior, and are inserted, by a strong tendinous lamina, into the lower and back part of the medial surface of the ramus and angle of the mandible • N. Supply: Like all other muscles of mastication the medial pterygoid is innervated by the anterior root (motor root) of the mandibular branch of the trigeminal nerve (V). • Actions: It contributes to following functions: – Elevation of the mandible (closes the jaw) – Minor contribution to protrusion of the mandible – Assistance in mastication – Excursion of the mandible; contralateral excursion occurs with unilateral contraction
    63. 63. Medial pterigoid insertion origin
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