Superficial nerves of the face and scalp

Facial nerve

In gross terms, the muscles of facial expression get their motor supply from the facial nerve. That is cranial nerve 7 and arises from the pontomedullary junction, between the abducent nerve (cranial nerve 6) and vestibulocochlear nerve (cranial nerve 8).

The facial nerve has 5 primary divisions, which are: Temporal, Zygomatic, Buccal, Mandibular and Cervical (Mnemonic: To Zanzibar By Motor Car).

If you spread your fingers and place them on the side of your face and neck, your fingers roughly correspond to the position of the branches.

• The temporal branches of the facial nerve are also known as the frontal branches of the facial nerve. They cross the zygomatic arch in order to reach the temporal region. There they supply the auricularis anterior and form a connection with the auriculotemporal branch of the mandibular nerve and also the zygomaticotemporal branch of the maxillary nerve. The corrugator supercili, frontalis, orbicularis oris gain supply from the more anterior branches of this nerve, and the temporal branches serve as an efferent limb of the corneal reflex (also known as the blink reflex).
• The zygomatic branches of the facial nerve are also known as the malar branches and they traverse the zygomatic bone in order to reach the lateral angle of the orbit. There the orbicularis oculi is supplied and the nerve joins some filaments of the lacrimal nerve.
• The facial nerve gives branches to the buccal area, which can be described as the area of the cheek, around the mouth and below the eyes. The most superficial branches of this nerve run beneath the skin and on the surface of the superficial muscles of the face. This nerve supplies these muscles including procerus and it also joins the medial angle with the infratrochlear and nasociliary branches of the ophthalmic nerve (V1 branch of the trigeminal nerve, discussed below). The deeper branches of the nerve supply the small nasal muscles. They travel beneath and supply both the quadratus labii superioris and zygomaticus, and go on to form an infraorbital plexus in association with the infraorbital branch of the maxillary nerve. The buccinators and orbicularis oris also get supply from the lowest of these deep branches.
• The marginal mandibular branch of the facial nerve travels forward underneath the platysma and anguli oris, and then supplies the chin, lower lip and continues to communicate with the mental branch of the inferior alveolar nerve.
• The cervical branch of the facial nerve is the lowest branch of the nerve and courses underneath, or deep to the platysma muscle. The nerve forms a distinctive series of arches as it progresses through the suprahyoid region and across the neck itself. Some branches of the nerve supply the platysma and also the depressor anguli oris. A specific branch also joins the cervical plexus branch (the cervical cutaneous nerve).

• The posterior auricular nerve is a another branch of the facial nerve which emerges from the stylomastoid foramen. At this point, it receives a communicating branch from the auricular branch of the vagus nerve. This nerve then ascends between the mastoid process and the external acoustic meatus, and then divides into the occipital and auricular branches. The auricular branch is responsible for supplying the intrinsic muscles on the surface of the external ear, as well as the auricularis posterior muscle. The occipital branch is a longer branch which travels posteriorly along the superior nuchal line found on the occipital bone (a lateral continuation of the external occipital protuberance), and supplies the occipitalis muscle.
  

Learn everything about the facial nerve here:

Trigeminal nerve

The sensory innervation to the face comes from the trigeminal nerve which is the only cranial nerve that arises directly from the pons. Its three branches are the Ophthalmic (V1), Maxillary (V2) and Mandibular (V3). Each of those branches supplies the corresponding region on the face. The trigeminal also supplies the muscles of mastication (medial and lateral pterygoids, temporalis and masseter).

Feeling a bit overwhelmed? Try easing yourself into this topic slowly with our cranial nerves quizzes and labeling exercises.

Nerves of the cervical plexus

The great auricular nerve is a branch of the cervical plexus and has nerve roots C2 and C3. Its functional role is to supply sensory innervation on the skin over the mastoid process, outer ear and parotid gland regions.

The greater occipital nerve is a spinal nerve from the medial branch of the dorsal primary ramus of the second cervical nerve. It emerges between the first two cervical vertebrae along with the lesser occipital nerve. The nerve then emerges from the suboccipital triangle which is defined by the rectus capitis posterior major, the obliquus capitus inferior and the obliquus capitis superior. It also emerges from beneath the lower border muscle (the obliquus capitis inferior). At that point, the nerve pierces the trapezius muscle, and travels superiorly to innervate the skin on the posterior scalp. It has a sensory function over the ear and parotid glands as well as the scalp of the head.

The lesser occipital nerve is also known as the small occipital nerve. It arises only from the root of the second cervical nerve and it emerges from the intervertebral foramen between the second and third cervical vertebrae. The greater occipital nerve also emerges from this foramen. The function of the lesser occipital nerve is to provide sensory innervation to the lateral area of the head posterior to the ear.