2 Objectives Identify the parts of the mandible. Know the type and formation of temporomandibular joint.Understand the attachment of the capsule and ligaments of the temporomandibular joint.Explain the mechanism of movements taking place at temporomandibular joint.Define the stability factors of the joint.Explain the muscles of mastication with their origin, insertion, nerve supply and actions.Discuss maxillary artery.
3 Gross Anatomy This is a synovial joint of condylar variety. COMPONENTS:Mandibular condylesArticular surfaces of Temporal boneCapsuleArticular discLigaments
4 ARTICULAR SURFACES- A. Upper part - a) Articular eminence, b) ant. part of mandibular fossa.B. Inferior surface -head of the mandible.
5 ARTICULAR DISC (MENISCUS) Fibro cartilaginous tissuesDisc divides the compartment into 2:Upper formed by Temporal bone and articular disc (Menisco temporal)Lower formed by mandible and articular disc (Menisco mandibular)
6 CAPSULE Fibrous membrane that surrounds the joint Covers the joint from all aroundThin above the disc and thick below itEncloses the discAttaches above: to the margins of the mandibular fossaAttaches below: to the neck of the mandibleThe inner aspect of capsule attaches to discAbove disc – capsule looseBelow disc - tight
10 MovementsElevationDepressionRetractionProtractionSide to side
11 Movements Side to side – grinding movements Mandible is alternately protracted and retracted with the two sides moving in opposite directions so that one side is protracted while the other is retractedActions combined with elevation and depression, rhythmically and alternately.Opening of the jaw (depression) ,is primarily passive or gravity assisted.
13 INNERVATION TRIGEMINAL NERVE: Mandibular div. SENSORY Auriculo temporal nerve: from the posterior division of the mandibular nerveMesseteric nerve: from the anterior division of the mandibular nerveMOTORMandibular division of trigeminal nerve
14 TemporalisIts a fan shaped muscle Covered by temporal fascia Origin: Medial wall of the temporal fossa and temporal fascia Insertion: Anterior margin of coronoid process and anterior border of the ramus of mandible Nerve supply: Deep temporal branch of anterior division of mandibular nerve
15 TEMPORAL FASCIA Attachment: Above: Superior temporal line Below: It splits into 2 layers and insert into respective borders of zygomatic bone
16 ACTION:ANT - Elevation of themandiblePOST – Retraction of mandibleMiddle fibres - ObliqueAnterior fibres – verticalPosterior fibres - Horizontal
17 Masseter It is quadrilateral in shape. Can be palpated in living subjects on clenching the teethIt consists of 2 layers :Superficial and deep.Origin:Lower margin and deep aspect of zygomatic archInsertion:Lateral surface of ramus and coronoid process of mandible
18 Protracts the mandible Nerve supply:Masseteric nerve from the anterior division ofmandibular nerve.Action:Elevates the mandibleSuperficial fibres:Protracts the mandible
19 Pterygoid muscles There are medial and lateral pterygoid muscles. They extend from the pterygoid plates and insert in the mandible.Lateral pterygoidPartotid ductBuccinatorMedial pterygoid
20 Lateral pterygoid It is a short, thick muscle consisting of two parts I) Upper headII) Lower headOrigin:Upper head: Infratemporal surface of greater wing of sphenoidLower head: Lateral surface of the lateral pterygoid plateInsertion: Pterygoid fovea (depression on the front of the neck of the mandible)Capsule of TMJUpper headLower headSome fibres of upper head may insertin the capsule of tempero-mandibular joint
21 Lat. Pterygoid - Attachment Upper headInfra temporalSufrace of greaterwing of sphenoidLower headLateral surface oflateral pterygoid plateNerve supply: Anterior division ofmandibular nerveAction: opening of mouth (Depression of mandible) by pulling forward thehead of mandible. Upper head – chewing, Lower head – protrusion.Side to side movements: combined action of medial and lateral pterygoid
22 Medial pterygoidIt consists of large deep head and small superficial head.Origin:Deep head: Arises from the medial surface of lat.pterygoid plateSuperficial head:Tuberosity of maxillaInsertion:Medial surface of ramus and angle of mandible.Nerve supply: Branch from the trunk of mandibular nerveDeep headSuperficial head
23 Deep fibresSuperficialfibresAction: Elevation of mandible. Together with lateral pterygoid, it helps in side to side chewing movement.
28 Clinical Anatomy (contd...) Submasseteric space infection:Infection around 3rd molar tooth may seep into the space between the attachment of masseter with mandible which leads to visible swelling and limitation of jaw movements
29 Clinical Anatomy (contd...) Paralysis of lateral pterygoid muscles causes the jaw to deviate towards the paralysed side on opening the mouth as a result of action of normal muscle.