Trigeminal nerve branches (sensory)
The trigeminal nerve provides sensory innervation to the face. The ophthalmic and maxillary nerves are exclusively sensory, whereas the mandibular nerve is mixed (containing both sensory and motor fibers). An important feature is that each of these branches gives off a small sensory meningeal branch near its origin.
The projection of the exit points of the cutaneous branches is determined by a single vertical line. It is drawn through the border between the inner and middle thirds of the supraorbital margin. The exit points are located along this line:
- 1st branch (n. ophthalmicus): cutaneous branches emerge directly at the level of the supraorbital margin.
- 2nd branch (n. maxillaris): represented by the infraorbital nerve (n. infraorbitalis), which emerges 0.5–0.8 cm below the infraorbital margin.
- 3rd branch (n. mandibularis): represented by the mental nerve (n. mentalis). Its exit point is located exactly at the midpoint of the distance between the alveolar and inferior margins of the mandible.
Facial nerve: pathway and parotid plexus
The facial nerve (n. facialis) contains motor fibers and is responsible for the function of the facial expression muscles. The nerve trunk exits the cranial cavity through the stylomastoid foramen (foramen stylomastoideum).
Immediately after emerging, the nerve penetrates the capsule into the bed of the parotid salivary gland. Deep within it, at a depth of 1–2 cm, the trunk divides into upper and lower branches that run parallel to the margin of the mandibular ramus. Connections form between these branches, creating the parotid plexus (plexus parotideus).
From the parotid gland, the nerve trunks emerge at varying distances from its anterior margin, pierce the proper fascia of the masseter muscle, and head toward the facial muscles.
Surgical significance: the branches of the facial nerve run in the deep layer of subcutaneous tissue. They approach the facial muscles exclusively from their deep surfaces. This is precisely why, during careful dissection of the skin and superficial subcutaneous tissue, the nerves remain intact—they lie deeper than the plane of the incision.
Branches of the facial nerve
The motor branches of the facial nerve project onto the skin along lines that diverge in a fan-like manner from a common point located inferior and anterior to the tragus of the ear.
Depending on which main branch (within the gland) they originate from, the following directions are distinguished:
The upper branch gives rise to:
- Temporal and zygomatic branches (rr. temporalis et zygomaticus) — run upward and forward toward the lateral angle of the eye.
- Buccal branches (rr. buccales) — run forward, projecting toward the midpoint of the distance between the ala of the nose and the angle of the mouth.
The lower branch gives rise to:
- Marginal mandibular branch (r. marginalis mandibulae) — runs horizontally along the inferior margin of the mandible (sometimes 1–2 cm below it).
- Cervical branch (r. colli) — descends vertically down into the neck.
Auriculotemporal nerve
The auriculotemporal nerve (n. auriculotemporalis) is a sensory branch originating from the mandibular nerve (n. mandibularis) immediately after its exit through the foramen ovale.
Its topography is closely related to major vessels:
- At its very origin, the nerve surrounds the middle meningeal artery (a. meningea media) with its roots.
- Then it passes superior to the maxillary artery (a. maxillaris).
- In the temporal region, the trunk is located medial to the superficial temporal artery (a. temporalis superficialis).
The nerve enters the parotid gland from beneath the condylar process of the mandible (through the posterior surface of the capsule). Then it ascends vertically, passing anterior to the external acoustic meatus. Within the substance of the gland, it gives off branches to the external acoustic meatus and tympanic membrane, as well as communicating branches to the facial nerve.
Briefly: answers to topical questions
What branches does the mandibular nerve give off?
The mandibular nerve gives off sensory, motor, and meningeal branches.
- Meningeal branch (r. meningeus spinosus) — branches off below the foramen ovale.
- Masseteric nerve (n. massetericus) — innervates the masseter muscle.
- Deep temporal nerves (nn. temporales profundi) — innervate the temporalis muscle.
- Medial and lateral pterygoid nerves (n. pterygoideus medialis et lateralis) — to the corresponding muscles.
- Buccal nerve (n. buccalis) — innervates the skin and mucosa of the cheek.
- Auriculotemporal nerve (n. auriculotemporalis) — innervates the temporal region, ear, and TMJ capsule.
- Lingual nerve (n. lingualis) — provides sensation to the anterior 2/3 of the tongue.
- Inferior alveolar nerve (n. alveolaris inferior) — gives off the mylohyoid nerve (n. mylohyoideus), mental nerve (n. mentalis), and incisive branch.
Which specific muscles do the temporal and zygomatic branches of the facial nerve innervate?
The temporal (frontal) and zygomatic branches of the facial nerve innervate the upper muscles of facial expression.
- Temporal / frontal branch (r. temporalis / r. frontalis) — innervates the frontal belly of the occipitofrontalis muscle (m. occipitofrontalis).
- Zygomatic branch (r. zygomaticus) — innervates the orbicularis oculi muscle (m. orbicularis oculi).
What branches does the ophthalmic nerve give off?
The ophthalmic nerve gives off a branch to the dura mater and three main branches within the orbit.
- Tentorial branch (r. tentorii) — branches within the tentorium cerebelli.
- Lacrimal nerve (n. lacrimalis) — gives off branches to the lacrimal gland and a communicating branch to the zygomaticotemporal nerve.
- Frontal nerve (n. frontalis) — divides into the supraorbital nerve (n. supraorbitalis) and supratrochlear nerve (n. supratrochlearis).
- Nasociliary nerve (n. nasociliaris) — gives off long ciliary nerves, anterior and posterior ethmoidal nerves, a branch to the lacrimal sac, and the external nasal nerve.
What branches does the maxillary nerve give off?
The maxillary nerve gives off a meningeal branch, branches in the pterygopalatine fossa, and branches from the pterygopalatine ganglion.
- Meningeal branch (r. meningeus medius) — runs with the frontal branch of the middle meningeal artery.
- Zygomatic nerve (n. zygomaticus) — innervates the skin of the zygomatic and temporal regions.
- Pterygopalatine nerves (nn. pterygopalatini) — run to the pterygopalatine ganglion.
- Posterior superior alveolar nerves (nn. alveolares superiores posteriores) to the upper posterior teeth and gingiva.
- Infraorbital nerve (n. infraorbitalis) — innervates the skin of the lower eyelid, nose, upper lip, and upper incisors and canines.
- Branches in the pterygopalatine ganglion — greater and lesser palatine nerves (n. palatinus major et nn. palatini minores), nasal branches, and nasopalatine nerve (n. nasopalatinus).
For quick memorization of the facial nerve branches, the "goosefoot" rule (hand projection) is used. Place your hand on the lateral surface of the face so that the thumb (I) vertically crosses the middle of the zygomatic arch. The fingers will indicate the course of the branches: thumb — temporal branch (r. temporalis); index finger (toward the corner of the eye) — zygomatic branch (r. zygomaticus); middle finger (above the lip) — buccal branches (rr. buccales); ring finger (along the mandibular margin) — marginal mandibular branch (r. marginalis mandibulae); little finger (onto the neck) — cervical branch (r. colli).
Class and exam questions
Where does the infraorbital nerve exit?
The infraorbital nerve (the second branch of the trigeminal nerve) emerges 0.5–0.8 cm below the infraorbital margin, strictly on the vertical line passing through the border of the inner and middle thirds of the supraorbital margin.
Through which foramen does the facial nerve exit the skull?
The trunk of the facial nerve leaves the cranial cavity through the stylomastoiding foramen (foramen stylomastoideum), after which it penetrates the parotid gland.
Why are facial nerve branches typically not damaged during facial skin incisions?
The branches of the facial nerve lie in the deep layer of subcutaneous tissue and enter the facial muscles from their deep surface. A superficial skin incision runs above this layer.
How does the auriculotemporal nerve relate to the meningeal artery?
At its base, the auriculotemporal nerve divides into two roots that loop around the middle meningeal artery (a. meningea media).
What else to study on this topic
- Formation and branching of the parotid plexus (plexus parotideus)
- Topography of the stylomastoid foramen and the facial nerve trunk
- Connections between the auriculotemporal and facial nerves within the salivary gland
- Fasciae and fascial spaces of the parotid-masseteric region
- Relationship of the auriculotemporal nerve with the temporal and maxillary arteries
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