Infratemporal fossa Dr A.Prasanna
Objectives The objective of the lecture : Is to discuss infratemporal fossa Muscles of mastication Maxillary artery Mandibular nerve Temporomandibular joint.
Boundaries of infratemporal fossa Roof: Infratemporal surface of greater wing of sphenoid bone A small part by sqamous part of temporal bone Medial wall— Lateral pterygoid plate Anterior wall—formed by posterior surface of body maxilla Lateral wall—by medial surface of ramus of mandible.
Contents of infratemporal fossa Lateral and medial pterygoid muscles Maxillary artery Mandibular nerve Chorda tympani nerve Maxillary nerve
Muscles of mastication
Muscles of mastication There are 4 muscles They are supplied by mandibular nerve They develop from 1st pharyngeal arch Muscles are : Masseter Temporalis Lateral pterygoid Medial prerygoid
Masseter Origin : lower border and deep surface of zygomatic arch Insertion : lateral surface of ramus of mandible Action : elevation and protrusion of mandible
Zygomatic arch & ramus of mandible
Temporalis Origin : temporal fossa Insertion : Coronoid process apex Anterior border of ramus of mandible Action : elevation and retraction of mandible
Temporal fossa & coronoid process
Lateral pterygoid Origin : Upper head from roof of infratemporal fossa Lower head from lateral surface of lateral pterygoid plate Insertion : Pterygoid fovea Capsule of tempromandibular joint Articular disc Action : Depresion , protrusion and side to side movement
Infratemporal surface – lateral pterygoid plate & pterygoid fovea
Relations of Lateral pterygoid It is triangular muscle Base in the front and apex in the back attached to pterygoid fovea From upper margin deep temporal nerves and vessels emerge Buccal nerve emerges between the two heads of muscles Maxillary artery lies superficial to the lower head of muscle Lingual nerve and inferior alveolar nerve emerge from the lower margin of muscle Middle meningeal artery and accessory middle meningeal artery passes deep to muscle
Lateral pterygoid relations
Medial pterygoid Origin : Superficial head from tuberosity of maxilla Deep head from medial surface of lateral pterygoid plate Insertion : medial side of angle of mandible Action : Elevation , protrusion and side to side movement
Tuberosity of maxilla -Lateral pterygoid plate & pterygoid fovea
Maxillary artery
Maxillary artery parts
Maxillary artery Beginning : posterior to the neck of mandible as a large terminal branch of external carotid artery Three parts First part: runs horizontally forwards between the neck of the mandible and sphenomandibular ligament On the lower border of lateral pterygoid muscle
Maxillary artery Second part : runs anterosuperiorly superficial to lower head of lateral pterygoid Third part : turns medially between the heads of lateral pterygoid and ends in the pterygopalatine fossa
Maxillary artery The artery gives branches to : External acoustic meatus Middle ear Muscles of the infratemporal region Skull bones Dura matter by middle meningeal artery Its branches accompanies nerves into infratemporal and pterygopalatine fossa
Maxillary artery The inferior alveolar artery descends with inferior alveolar nerve To enter into mandibular foramen It courses through the mandibular canal to supply teeth, gums and mandible It also supplies skin over the chin and lip through the mental artery It sends mylohyoid artery along with the mylohyoid nerve The veins drain into pterygoid venous plexus
Branches of the maxillary artery
Mandibular nerve
Mandibular nerve It is a branch of trigeminal nerve Arises from trigeminal ganglion Passes through foramen ovale It is joined by motor root in the foramen ovale and emerges as mixed nerve It divides immediately as anterior ( mainly motor) and posterior ( mainly sensory) divisions
Branches from trunk Meningeal branch enters skull with middle meningeal artery Nerve to medial pterygoid
Branches from anterior division Large sensory buccal nerve Passes between the two heads of lateral pterygoid Runs on the surface of buccinator muscle It forms plexus with buccal branch of facial nerve It supplies entire thickness of cheek from skin to mucous membrane Motor branches of anterior division are : Nerve to lateral pterygoid Deep temporal nerves Nerve to masseter
Branches from posterior division Auriculotemporal nerve Inferior alveolar nerve Mylohyoid nerve Lingual nerve
Auriculotemporal nerve It arises by two roots It receives post ganglionic parasympathetic fibers from otic ganglion for parotid gland Preganglionic fibers reach from glossopharyngeal nerve Roots surround middle meningeal artery
Inferior alveolar nerve It is a large branch of the posterior division It runs downwards with artery between the pterygoid muscles They give rise to mylohyoid branch Then enters mandibular foramen In the body of the mandible it supplies teeth and gums Sends mental branch which supplies skin of chin and lower lip Mylohyoid nerve only motor of posterior division supplies mylohyoid and anterior belly of digastric muscles The nerve is joined by submental artery in the digastric triangle Mylohyoid branch
Ligual nerve It is sensory to anterior two thirds of tongue , floor of mouth and gums It is medial to mandible It is in front of inferior alveolar nerve The nerve is joined by chorda tympani nerve , a branch of facial nerve Chorda tympani nerve brings preganglionic parasympathetic fibers to submandibular gland And taste sensation for anterior 2/3rds of tongue
Mandibular nerve
Temporomandibular joint Type :Synovial joint Sub type : Hinge joint
Articular surfaces Head of the mandible With mandibular fossa and articular tubercle of the temporal bone They are separated by articular disc Which divides joint cavity into upper and lower parts
Ligaments Fibrous capsule : is attached to margins of articular surfaces Laterally is thickened to form lateral ligament It is triangular with base attached to zygomatic arch With apex attached to lateral side of neck of mandible
Ligaments Articular disc is oval in shape Fused with capsule around the periphery The upper surface is concavoconvex to fit articular tubercle and mandibular fossa Its concave inferior surface fits the head of he mandible
Ligaments The capsule and the lateral ligament are the only proper ligaments Sphenomandibular and the stylomandibular ligaments Do not add any strength to the joint Muscles of mastication provide the required strength Similar to joints maintained by muscle strength- the joint is prone for dislocation
Ligaments Sphenomandibular ligament extends from spine of sphenoid to lingula near the margin of the mandibular foramen It is piercred by mylohyoid nerve The ligament is the remnant of 1st pharyngeal arch
Relations Anterior Posterior Above Medially – Auriculotemporal nerve Lateral pterygoid Posterior Parotid gland Above Floor of middle cranial fossa Medially – Auriculotemporal nerve
Blood supply Blood supply Superficial temporal artery Maxillary artery
Nerve supply Nerve supply Auriculo-temporal nerve – from the posterior division of mandibular nerve Masseteric nerve – from anterior division of mandibular nerve
Movements of joint Protraction – pulling the jaw forwards Retraction – it is reverse movement of protraction Depression- lowering of jaw Elevation – opposite of depresstion Side to side and grinding movement
Muscles acting on the joint Protraction – lateral and medial pterygoid Retraction – posterior fibers of temporalis Depression- lateral pterygoid, digastric and infrahyoid muscles Elevation – temporalis, masseter and medial pterygoid Side to side and grinding movement – produced by muscles of opposite side acting alternately
Clinical anatomy Dislocation of joint
Learning Outcomes At the end of the lecture, students should be able to: Outline the boundaries and contents of the infratemporal fossa Describe the origin,insertion,nerve supply and action of muscles of mastication. Describe the origin,course, branches and distribution of maxillary artery Describe the origin,course, branches and distribution of mandibular nerve. Discuss the type,sub type of temperomandibular joint Articular surfaces Ligaments Relations Blood supply Nerve supply Movements Muscles acting on temperomandibular joint Outline the clinical anatomy of the temperomandibular joint