Where: SCALP layer 4, the loose areolar tissue
Risk: meningitis, sinus thrombosis, skull osteomyelitis.
Also: blood spreads freely in this layer. The frontal belly has no bony attachment, so blood tracks into the eyelids → bilateral black eyes.
Where: corners of the mouth → bridge of the nose
Risk: cavernous sinus thrombosis. CN VI first (lateral gaze palsy), then CN III, IV, V1, V2. Proptosis, chemosis.
“Angry Superheroes Crash.”
| Epidural | Subdural | |
|---|---|---|
| Vessel | Middle meningeal artery (pterion fracture) | Bridging veins |
| Space | Skull ↔ dura | Dura ↔ arachnoid |
| CT shape | Biconvex / lens | Crescent |
| Sutures | Does not cross | Crosses |
| Classic clue | Lucid interval → rapid decline | Elderly, alcohol use, slower onset |
Epidural = Egg (lens) + Artery. Subdural = Sickle (crescent) + veins.
| Buccal branch of CN VII | Buccal nerve (CN V3) | |
|---|---|---|
| Type | Motor | Sensory |
| Origin | Anterior border of parotid gland | Anterior division of CN V3; exits between the heads of lateral pterygoid |
| Course | Across masseter with the parotid duct | On buccinator, then pierces it |
| Supplies | Buccinator, orbicularis oris, zygomaticus major / minor | Skin of cheek, buccal mucosa, buccal gingiva of lower molars |
| Lesion | Food collects in the vestibule, drooling | Numb cheek |
| Superficial temporal artery | Deep temporal arteries (anterior + posterior) | |
|---|---|---|
| Origin | Terminal branch of external carotid artery (in parotid) | Maxillary artery, part 2 (pterygoid part) |
| Position | Superficial to temporalis fascia, anterior to tragus | Deep to temporalis, on the bone |
| Travels with | Auriculotemporal nerve (behind it) | Deep temporal nerves (anterior division of CN V3) |
| Clinical | Pulse anterior to tragus; biopsy for giant cell arteritis | Supply temporalis |
| Carotid sinus | Carotid body | |
|---|---|---|
| Location | Dilation at origin of internal carotid artery | Small mass at the bifurcation (C4) |
| Senses | Blood pressure (baroreceptor) | O2 / CO2 / pH (chemoreceptor) |
| Nerve | CN IX for both (carotid sinus nerve). Aortic arch receptors use CN X. “IX at the neck, X at the arch.” | |
| Finding | Structure | Nerve | Key point |
|---|---|---|---|
| Can’t close the eye | Orbicularis oculi | CN VII (temporal + zygomatic branches) | Risk of exposure keratitis; no ptosis |
| Complete ptosis | Levator palpebrae superioris (skeletal) | CN III | Plus “down and out” eye |
| Mild ptosis (~2 mm) | Superior tarsal (Müller’s) muscle (smooth) | Sympathetics | Horner: ptosis, miosis, anhidrosis |
| Can’t look down | Inferior rectus paralyzed | CN III | Muscle loses its own action |
| Can’t look up after orbital floor fracture | Inferior rectus entrapped | — | Tethered muscle blocks the opposite action; vertical diplopia |
All three foramina line up roughly on a vertical line through the pupil.
| Muscle | Where | Action → expression | CN VII branch | High-yield / clinical |
|---|---|---|---|---|
| Frontal belly of occipitofrontalis | Forehead; no bony attachment; joins epicranial aponeurosis | Raises eyebrows, wrinkles forehead → surprise | T | No bony attachment → scalp blood tracks into eyelids |
| Occipital belly of occipitofrontalis | Superior nuchal line → aponeurosis | Retracts scalp | PA | Branch given off before the parotid |
| Orbicularis oculi — orbital part | On the bony orbital rim | Tight closure → squint | T Z | Efferent limb of corneal reflex. Paralysis → can’t close eye → exposure keratitis |
| Orbicularis oculi — palpebral part | Within the eyelids | Gentle closure → blink | T Z | |
| Zygomaticus major | Zygomatic bone → angle of mouth | Corner of mouth up and out → smile | Z B | Lateral to minor |
| Zygomaticus minor | Zygomatic bone → upper lip | Elevates upper lip → sneer / sadness | Z B | Deepens nasolabial fold |
| Buccinator | Pterygomandibular raphe + maxilla/mandible → angle of mouth | Presses cheek to teeth, blowing → trumpeter | B | Pierced by parotid duct. Raphe shared with superior constrictor. Paralysis → food in oral vestibule. Sensation = buccal nerve (V3) |
| Orbicularis oris | Sphincter within lips | Closes / purses lips → kiss, whistle | B upper · M lower | Paralysis → drooling, liquid leaks from that side |
| Depressor anguli oris | Oblique line of mandible → angle of mouth (triangular) | Pulls corner of mouth down → frown | M | “Anguli” = angle. Antagonist of zygomaticus major |
| Mentalis | Mandible below incisors → chin skin | Elevates / protrudes lower lip, wrinkles chin → pout, doubt | M | Over the mental protuberance |
| Platysma | Superficial fascia of upper chest → mandible, mouth | Tenses neck skin, depresses mouth → grimace | C | External jugular vein and cervical plexus nerves lie deep to it |
Hand trick: palm over the ear, fingers spread across the face. Thumb = temporal, index = zygomatic, middle = buccal, ring = mandibular, pinky = cervical.
| Muscle | Attachments | Action | Nerve | Key point |
|---|---|---|---|---|
| Masseter | Zygomatic arch → lateral ramus and angle | Elevates (closes); superficial part helps protrude | Masseteric nerve (anterior division) via mandibular notch | Parotid duct crosses its surface |
| Temporalis | Temporal fossa → coronoid process (deep to zygomatic arch) | Vertical fibers elevate; posterior horizontal fibers retract | Deep temporal nerves (anterior division) | Temporal fossa communicates with the infratemporal fossa deep to the arch |
| Medial pterygoid | Medial surface of lateral pterygoid plate → medial angle | Elevates, helps protrude and grind | Nerve to medial pterygoid (main trunk) | “Sling” with masseter. Pterygomandibular space lies between it and the ramus |
| Lateral pterygoid | Upper head: greater wing · Lower head: lateral surface of lateral pterygoid plate → neck of condyle + TMJ disc | Depresses + protrudes; one side → chin to opposite side | Nerve to lateral pterygoid (anterior division) | Only opener. Anterior TMJ dislocation |
Masseter, Medial pterygoid, teMporalis = close. Lateral pterygoid = open.
Also weak bite on the right, ipsilateral facial sensory loss (V3 territory), and general sensation lost on the anterior 2/3 of the tongue. No loss of tears or nasal secretion (that is CN VII).
| Artery | CN V2 nerve | Route / opening | Territory | |
|---|---|---|---|---|
| Posterior superior alveolar artery | ⟷ | Posterior superior alveolar nerve | Down onto the back of the maxilla (branches before the orbit) | Upper molars, maxillary sinus |
| Infraorbital artery | ⟷ | Infraorbital nerve | Inferior orbital fissure → infraorbital groove → canal → infraorbital foramen | Lower eyelid, side of nose, cheek, upper lip |
| ↳ Middle + anterior superior alveolar arteries | ⟷ | Middle + anterior superior alveolar nerves | Branch inside the infraorbital canal | Premolars, canine, incisors |
| Descending palatine → greater + lesser palatine arteries | ⟷ | Greater + lesser palatine nerves | Palatine canal → greater / lesser palatine foramina | Hard and soft palate |
| Sphenopalatine artery (terminal) | ⟷ | Nasopalatine + posterior nasal nerves | Sphenopalatine foramen → nasal cavity | Lateral wall and septum · posterior epistaxis |
| Artery of the pterygoid canal | ⟷ | Nerve of the pterygoid canal | Pterygoid canal (backward) | Carries greater + deep petrosal fibers (not V2 itself) |
| Pharyngeal artery | ⟷ | Pharyngeal nerve | Backward to nasopharynx | Roof of nasopharynx |
Order through the fossa: “Teeth, Eye, Palate, (back), Nose” — posterior superior alveolar first, sphenopalatine last.
| Part | Artery | CN V3 nerve | Opening / route | |
|---|---|---|---|---|
| 1 | Middle meningeal artery | ⟷ | Meningeal branch of CN V3 (main trunk) | Foramen spinosum (nerve re-enters skull) |
| 1 | Accessory meningeal artery | ⟷ | CN V3 trunk | Foramen ovale |
| 1 | Inferior alveolar artery | ⟷ | Inferior alveolar nerve (posterior division) | Mandibular foramen (under the lingula) → mandibular canal |
| 1 | ↳ Mylohyoid artery | ⟷ | Nerve to mylohyoid | Mylohyoid groove → mylohyoid, anterior belly of digastric |
| 1 | ↳ Mental artery | ⟷ | Mental nerve | Mental foramen (below lower 2nd premolar) → chin, lower lip |
| 2 | Deep temporal arteries | ⟷ | Deep temporal nerves (anterior division) | Up, deep to temporalis |
| 2 | Masseteric artery | ⟷ | Masseteric nerve | Laterally through mandibular notch |
| 2 | Pterygoid branches | ⟷ | Nerves to pterygoids | Into lateral / medial pterygoid |
| 2 | Buccal artery | ⟷ | Buccal nerve (sensory) | Forward onto buccinator |
| Pair | Relationship | Why it’s tested |
|---|---|---|
| Superficial temporal artery + auriculotemporal nerve | Ascend together anterior to the tragus; nerve runs behind the artery (superficial temporal vein alongside) | Identify the artery by its companion nerve; pulse point |
| Auriculotemporal nerve around middle meningeal artery | Two roots encircle the artery, then unite and run back deep to the neck of the mandible | Classic identification landmark in the infratemporal fossa |
| Deep temporal arteries + deep temporal nerves | Run up together between temporalis and the skull | Deep vs superficial temporal comparisons |
| Lingual nerve + submandibular duct | Double-crosses the duct: lateral → under → medial | Surgery on the duct or stones risks the nerve |
| Chorda tympani → lingual nerve | Joins it from behind, deep to lateral pterygoid | Lingual nerve distal to this carries taste + parasympathetics |
| Lingual + inferior alveolar nerves | Lie together in the pterygomandibular space (medial pterygoid ↔ ramus); lingual is anterior | Inferior alveolar nerve block often numbs the tongue too |
| Inferior alveolar artery + inferior alveolar nerve | Enter the mandibular foramen together under the lingula | Nerve gives off nerve to mylohyoid just before entering |
| Parotid duct + buccal branch of CN VII | Cross masseter together; transverse facial artery runs just above | Duct turns medially at the anterior border of masseter |
| Mandibular branch of CN VII over facial artery + facial vein | Crosses superficial to both at the lower border of the mandible | At risk in submandibular gland surgery |
| Facial artery + facial vein | Artery tortuous and anterior; vein straighter and posterior | Tell them apart on the specimen |
| Inside the parotid gland | Superficial → deep: CN VII → retromandibular vein → external carotid artery | “Never Very Arterial” |
| Middle meningeal artery + meningeal branch of CN V3 | Share the foramen spinosum | Foramen contents |
| Position relative to lateral pterygoid | Structures |
|---|---|
| ⬆ Upper border | Deep temporal nerves (+ arteries) · masseteric nerve (+ artery) |
| ↔ Between the two heads | Buccal nerve (+ buccal artery). The maxillary artery sometimes passes here. |
| ⬇ Lower border | Lingual nerve (anterior) · inferior alveolar nerve (posterior) — chorda tympani joins the lingual nerve here |
| Lateral (superficial) | Ramus of the mandible, temporalis tendon, masseter · maxillary artery part 2 (usually) · pterygoid venous plexus |
| Medial (deep) | Medial pterygoid · CN V3 trunk (from foramen ovale) · otic ganglion · origin of middle meningeal artery · chorda tympani |
| Posterior | Maxillary artery part 1 behind the neck of the mandible · auriculotemporal nerve around the middle meningeal artery · TMJ |
| Anterior | Maxillary artery part 3 → pterygomaxillary fissure → pterygopalatine fossa |
“My Dog Likes Bones”
“ALI”
Superior alveolar nerves back → front: “P-M-A” (posterior before the orbit; middle and anterior in the canal).
| Region | Taste | General sensation |
|---|---|---|
| Anterior 2/3 | CN VII (chorda tympani via lingual nerve) | CN V3 (lingual nerve) |
| Posterior 1/3 | CN IX | CN IX |
| Epiglottis region | CN X (internal branch of superior laryngeal nerve) | CN X |
Taste front to back: “7 – 9 – 10.”
Trigeminal exits “Standing Room Only”: V1 superior orbital fissure · V2 rotundum · V3 ovale.
| Direction | Branch | Course |
|---|---|---|
| ➡ Anterior (3) | Superior thyroid artery | First branch → down to thyroid; gives superior laryngeal artery (with internal branch of superior laryngeal nerve through thyrohyoid membrane) |
| Lingual artery | At greater horn of hyoid → deep to hyoglossus | |
| Facial artery | Grooves submandibular gland → hooks over mandible anterior to masseter | |
| ⬆ Medial (1) | Ascending pharyngeal artery | Straight up along the pharynx |
| ⬅ Posterior (2) | Occipital artery | Along lower border of posterior belly of digastric |
| Posterior auricular artery | Along upper border of posterior belly of digastric, behind the ear | |
| ⬆ Terminal (2) in parotid | Maxillary artery | Behind neck of mandible → infratemporal fossa |
| Superficial temporal artery | Straight up anterior to tragus (pulse point) |
“Some Anatomists Like Freaking Out Poor Medical Students.” Practical tip: the internal carotid artery has no branches in the neck.
Behind lateral pterygoid · branches go through holes
“DAM I Am”
On lateral pterygoid · branches go to muscles
Named for the muscle they feed
Beyond the muscle · branches follow CN V2
“Teeth, Eye, Palate, (back), Nose”
| Ganglion | Preganglionic | Postganglionic route | Target | Hook |
|---|---|---|---|---|
| Ciliary | CN III | Short ciliary nerves | Sphincter pupillae, ciliary muscle | — |
| Pterygopalatine | CN VII → greater petrosal nerve | Zygomatic (V2) → lacrimal nerve (V1) | Lacrimal gland, nasal + palatal glands | Grief (tears) |
| Submandibular | CN VII → chorda tympani (via lingual nerve) | Direct / back along lingual nerve | Submandibular + sublingual glands | Chomp (chin glands) |
| Otic | CN IX → lesser petrosal nerve | Auriculotemporal nerve | Parotid gland | “Oh, Parotid” |
| Gland | Secretion | Duct opens |
|---|---|---|
| Parotid | Serous | Parotid papilla, opposite upper 2nd molar |
| Submandibular | Mixed | Sublingual papilla (floor of mouth) |
| Sublingual | Mostly mucous | Many small ducts on sublingual fold |
Surface line: tragus → midpoint between ala of nose and upper lip (middle third).
Scalp sensation: supraorbital + supratrochlear nerves (V1) in front · auriculotemporal nerve (V3) at the temple · lesser and greater occipital nerves behind. Motor to the scalp muscles: temporal (frontal belly) and posterior auricular (occipital belly) branches of CN VII.
| Scenario | Structure | Key finding / answer |
|---|---|---|
| Blow to the temple, lucid interval, then decline | Middle meningeal artery at the pterion | Epidural hematoma, biconvex |
| Older adult: temporal headache, jaw claudication, tender temple, vision loss | Superficial temporal artery | Giant cell arteritis → high ESR; temporal artery biopsy; start steroids immediately |
| Squeezed a pimple near the nose; now proptosis and lateral gaze palsy | Facial → angular → superior ophthalmic veins | Cavernous sinus thrombosis; CN VI first |
| Posterior nosebleed that won’t stop | Sphenopalatine artery | Terminal branch of maxillary artery through sphenopalatine foramen |
| Lower 3rd molar extraction → numb tongue, altered taste | Lingual nerve | Ipsilateral anterior 2/3: general sensation + taste; ↓ submandibular/sublingual saliva if cut before the ganglion |
| Inferior alveolar nerve block also numbs the tongue | Pterygomandibular space | Lingual nerve lies next to the inferior alveolar nerve |
| Orbital floor (blowout) fracture | Infraorbital nerve + inferior rectus | Numb cheek / upper lip; can’t look up (entrapment) |
| Wide yawn, can’t close mouth | Lateral pterygoid / TMJ | Anterior dislocation; reduce down then back |
| Sweating and flushing on the cheek while eating after parotidectomy | Auriculotemporal nerve | Frey syndrome |
| Painful parotid swelling, worse with chewing | Parotid capsule | Mumps; great auricular nerve |
| Submandibular gland excision → asymmetric lower lip | Mandibular branch of CN VII | Can’t depress corner of mouth / lower lip |
| Can’t close one eye after facial injury | Orbicularis oculi (CN VII) | Exposure keratitis; lubricate and tape the eye |
| Shingles on the forehead + vesicles on the tip of the nose | Nasociliary nerve (V1) | Hutchinson sign → high risk of eye involvement |
| Scalp laceration gapes and bleeds heavily | Aponeurosis + dense connective tissue | Belly traction + vessels held open |
| Scalp injury → bilateral black eyes | Loose areolar tissue | Blood tracks forward (frontal belly has no bony attachment) |
| CN VII terminal branches | To Zanzibar By Motor Car |
| CN VII in the facial canal | Good Sounds Come |
| CN VII before the parotid | Please Don’t Stop |
| CN V3 anterior division | My Dog Likes Bones |
| CN V3 posterior division | ALI |
| Mastication | M’s Munch, Lateral Lowers |
| External carotid branches | Some Anatomists Like Freaking Out Poor Medical Students |
| Maxillary artery parts | Holes, Muscles, V2 · part 1 “DAM I Am” |
| Parotid contents | Never Very Arterial (nerve → vein → artery, superficial → deep) |
| Danger triangle | Angry Superheroes Crash |
| Parasympathetics | Grief (pterygopalatine) · Chomp (submandibular) · Oh, Parotid (otic) |
| Taste | 7 – 9 – 10, front to back |
| Pharyngeal arches | Arch 1 chews · Arch 2 smiles · Arch 3 swallows · Arches 4/6 talk |
| Hematomas | Epidural = Egg + Artery · Subdural = Sickle + veins |
Answer first, then open each one to check.