Muscles of Mastication
- From 1st Pharyngeal Arch
Muscles of Mastication (All by CN V₃)
Primary Muscles | Insertion | Notes |
Temporalis | • Coronoid process of mandible | • Elevation > Retraction |
Masseter | • Outer surface of ramus of mandible | • Elevation ↳ Strongest muscle of mastication ↳ Best muscle for elevation |
Medial Pterygoid | • Inner surface of ramus of mandible | • Elevation > Protrusion • Only muscle supplied by trunk of CN V₃ |
Lateral Pterygoid | • Capsule of TMJ | • Depression > Protrusion • Only depressing muscle of mastication |
- NOTE: Medial pterygoid plate : Doesn't give origin to pterygoid muscles.
- Protrusion
- Lateral > medial pterygoid
- Most apt answer is both
- Mnemonic: Teri (Both pterygoids) parayan jaw Protrude ()
- Opening the jaw/ depression of the mandible
- Lateral pterygoid muscle
- Remaining 3 muscles: Elevation of mandible
- Masseter > Temporalis & Medial pterygoid
- Side movement
- Alternate action of Lateral & Medial Pterygoids
Trismus (Lockjaw)
- Silent trismus → Medial pterygoid
- Trismus while yawning/opening mouth → Lateral pterygoid
Accessory Muscle
- Buccinator
- Motor: Buccal branch of Facial nerve (CN VII)
- Sensory: Buccal nerve of Mandibular nerve (V₃)
- Pierced by: Stenson's duct (Parotid duct)
- Insertion: Mandible
- Mnemonic: Bucky (Buccinator) and Steve (Stenson) → 2 Cap America
Development & Nerve Supply
Mandibular nerve (V₃) — motor and sensory
- Mixed nerve
- Derived from 1st pharyngeal arch
- Largest and thickest branch of trigeminal nerve
- Root value: C₅, C₆, C₇, C₈, T₁
- Passes through foramen ovale (both sensory & motor components).
- All muscles supplied by V3 except
- Medial Pterygoid → Main trunk of 5th CN
- Mneumonic:
- Mandi (Mandibular) aytttulla oru auntie (Anterior ) always chew (mastication) → Was post (Posterior ) and sensitive (Sensory)
- She had a good aura (Auriculotemporal nerve) and good tongue (Lingual nerve) , but no lower teeth (Inferior alveolar nerve)
Divisions of Mandibular Nerve
- After passing through otic ganglion:
- Anterior division
- Posterior division
Anterior Division | (Motor>Sensory) |
Motor (SVE) | Muscle supplied |
Masseteric nerve | Masseter |
Deep temporal nerves | Temporalis |
Nerve to lateral pterygoid | Lateral pterygoid |
Sensory (GSA) | ㅤ |
Buccal Nerve | • Pierces buccinator muscle [Does NOT supply] Supplies: • Skin of cheek • Mucosa of cheek |
Posterior Division | (Mostly Sensory) |
Lingual Nerve | Sensory • GS to anterior 2/3 of tongue Parasympathetic Post ganglionic ↳ from submandibular ganglion ↳ to Submandibular & sublingual gland • M/c injured during Wharton’s/submandibular duct surgery. |
Inferior alveolar nerve | • Nerve to mylohyoid → Mylohyoid + Anterior belly of digastric • Mental nerve → Skin of chin |
NOTE
Structure | Pierced by but not supplied by | Supplied by |
Buccinator | Buccal N (branch of V3) | Buccal branch of facial nerve – motor |
Parotid | Facial nerve | Auriculotemporal N |
Inferior Alveolar artery
- Runs with the inferior alveolar nerve to supply the lower teeth.
- Gives off:
- Mental Artery: Exits through the mental foramen to supply the chin.
- Mylohyoid branch: Supplies the mylohyoid muscle.
- Mnemonic: Use lower teeth () when Myran (Mylohyoid A) becomes mental (Mental A)
Otic ganglion:
Relations of otic ganglion
- Topographical relation with V₃
- Mandelu Otta
- No synapse occurs here
Relations | Muscle |
Anterior | Medial Pterygoid |
Posterior | MMA |
Lateral | V3 Nerve/ Mandibular N |
Medial | TVP |
Roof | Foramen ovale |
Topographic nerve
- Trigeminal nerve (V)
- All ganglia are topographically connected to trigeminal nerve
- Carries postganglionic fibres in parasympathetic pathway
Roots of Otic Ganglion
- Parasympathetic (secretomotor root)
- From glossopharyngeal nerve (CN IX) via lesser petrosal nerve
- Relay in otic ganglion
- Postganglionic fibers travel with auriculotemporal nerve (branch of V3)
- Auriculotemporal nerve (V3) pass through without relay
- Supply parotid gland
- Sympathetic root
- From plexus around middle meningeal artery
- postganglionic fibers from superior cervical ganglion
- Pass through ganglion without synapse
- Vasomotor to parotid gland
Temporomandibular Joint (TMJ)
- Type: Synovial condylar joint
- Articular disc:
- Fibrocartilage; divides joint cavity
- Upper cavity: Sliding/gliding
- Lower cavity: Rotation
Supports:
True support
- Lateral TM ligament
- prevent hyper retraction
False support
- Stylomandibular ligament
- Sphenomandibular ligament
Blood Supply:
- ECA Terminal branches
- Maxillary artery
- Superficial temporal artery
Nerve Supply:
- Auriculotemporal nerve
- Masseteric nerve
- Method of identification
- 1st localise ramus
- Outside ramus → masseter
- Inside →
- Lateral pterygoid
- Medial pterygoid (medially in contact with teeth)
Muscles of Facial Expression
Overview
- Derived from: 2nd pharyngeal arch
- Nerve supply: Facial nerve (CN VII)
- Action: Move skin of face, important for facial expressions
Classification by Regions
1. Scalp
- Occipitofrontalis
- Frontal belly: Raises eyebrows, wrinkles forehead
- Occipital belly: Pulls scalp backward
- Connected by epicranial aponeurosis (galea aponeurotica)
- Mnemonic: Galea aponeurotica → Galileo’s brain → In skull
2. Around the Eye
- Orbicularis oculi
- Orbital part: Forceful closure
- Palpebral part: Gentle closure (blinking)
- Lacrimal part: Helps drainage of tears
- Attach to Frontal process of maxilla
- Corrugator supercilii:
- Draws eyebrows medially and downward
- frown
- Attach to Median superciliary arch
- Mnemonic: Super silly () people always bring us down (down and medially)
3. Around the Nose
- Nasalis
- Compressor naris: Compresses nostrils
- Dilator naris: Widens nostrils
- Procerus:
- Wrinkles skin over nose bridge
- at root of nose
- Attach to Superior nasal bone
- Depressor septi nasi:
- Pulls nasal septum downward
4. Around the Mouth
- Orbicularis oris:
- Closes lips, puckers lips
- Kissing muscle
- Repaired in Cleft lip
- Bring Oreo (Orbicularis oris) ad → kiss me → close ur eyes, miss me
- Buccinator
- Compresses cheek against teeth
- Helps in mastication, whistling/blowing muscle.
- Neonatal suckling and oral phase of swallowing
- Pierced by parotid duct
Muscle | Action |
Levator labii superioris | Elevates upper lip |
Levator anguli oris | Elevates angle of mouth |
Zygomaticus major | Laughing muscle; elevates & draws angle of mouth laterally (smile) Major Laugh |
Zygomaticus minor | Elevates upper lip |
Risorius | Retracts angle of mouth (fake smile) Rise (Risorius) with a fake smile |
Depressor anguli oris | Depresses angle of mouth (sad face) |
Depressor labii inferioris | Depresses lower lip |
Mentalis | Protrudes lower lip (pouting) |
5. Neck
- Platysma
- Tenses skin of neck
- Depresses mandible
- Mnemonic: Bring his Neck (Skin of neck) on a plate (Platysma)
Parotid Duct (Stensen’s Duct)
- Runs over masseter (superficial) → Turns medially
- Pierces:
- Buccal fat
- Buccopharyngeal fascia
- Buccinator muscle
- Opens at parotid papilla
- opposite upper 2nd molar - maxillary molar
- NOTE: Koplik → Lower 2nd molar
Structures Piercing Buccinator
- Stenson's Duct / Parotid duct
- Buccal br. Of Mandibular (V3) NV
- Mucus glands of buccopharyngeal Fascia
NOTE
- Facial N supplies but does not pierce
Clinical points:
- Parotitis
- Koplik's spots
- Duct can be cannulated for imaging
Salivary gland swelling D/Ds
- Sialosis → Salivary gland swelling in alocoholics
ㅤ | ㅤ |
HIV Infection ↳ BLEL / ↳ Benign Lymphoepithelial lesions | • CD8+ T lymphocytes infiltrate • HLA-DR5 • Positive serologic test |
Sjogren’s Syndrome | • CD4 + T lymphocytes infiltrate • HLA-DR3, DRw52 • Ro La antibodies |
Sarcoidosis | • Granulomas in salivary glands • CD4/CD8 ratio > 3.5 : 1 |
Structures Passing Through Parotid Gland
Superficial → Deep
- Facial nerve (CN VII) through Patey’s plane
- Does not innervate the gland
- Divides into:
- Temporal
- Zygomatic
- Marginal mandibular
- Buccal
- Cervical
- Retromandibular vein
- External carotid artery
Mnemonic: Avnu (artery → vein → nerve from Deep → Sup) Pattiye (Patey)
Note
- Parotid nodes present on superficial surface
Made with Bullet