The face contains an abundance of small muscles that work together to help us show our emotions. You can thank these muscles for everything your face does, from smiling and frowning to making funny faces in group pictures!
Naturally, for these muscles to work, there are many tiny nerves, arteries, and veins that supply them. Let’s start off with the sensory innervation of the face.
Almost all of its sensory innervation is provided by the fifth cranial nerve, also known as the trigeminal nerve, which has three divisions.
Its superior division is known as the ophthalmic nerve, and it provides sensory innervation for the part of the scalp anterior to the vertex of the head, the forehead, the upper eyelids, the dorsum of the nose and the roof of the nasal cavity.
The ophthalmic nerve arises from the trigeminal ganglion, leaves the skull through the superior orbital fissure, and enters the orbit, where it gives rise to three branches; the frontal nerve, the nasociliary nerve and the lacrimal nerve.
So let’s look at them one by one! The frontal nerve runs across the roof of the orbit, and it gives rise to the supraorbital and the supratrochlear nerves.
The supraorbital nerve exits the orbit through the supraorbital notch and supplies the skin of the anterior part of the scalp, the anterolateral forehead, and the middle of the upper eyelids.
The supratrochlear nerve exits the orbit lateral to the trochlea and supplies the skin of the anteromedial forehead.
Next is the nasociliary nerve, which divides into the anterior ethmoidal, the posterior ethmoidal, and the infratrochlear nerves.
The anterior ethmoidal nerve travels a long way through the nasal cavity, and exits between the nasal bone and the lateral nasal cartilage as the external nasal nerve.
It supplies sensory innervation to the skin of the dorsum of the nose, the nasal ala, and the nasal vestibule. So, whenever the tip of your nose feels itchy, you know it’s that pesky external nasal nerve.
The infratrochlear nerve is the terminal branch of the nasociliary nerve, and exits the orbit on the medial angle. It innervates the medial part of the upper eyelid, the skin around it, and lateral to the root of the nose.
The last branch of the ophthalmic nerve is the lacrimal nerve, which exits the orbit on the lateral angle and innervates the lateral side of the upper eyelid, and the skin around it.
The intermediate division of the trigeminal nerve is called the maxillary nerve and supplies the skin of the anterior part of the temporal region, the skin over the zygomatic bone, the lower eyelid, the cheek, the side of the nose, the nasal septum, and the upper lip.
It travels anteriorly from the trigeminal ganglion, leaves the skull through the foramen rotundum in the sphenoid bone, and enters the pterygopalatine fossa.
It then passes through the inferior orbital fissure to enter the orbit, where it gives off the zygomatic nerve.
The maxillary nerve continues on, and travels within the infraorbital groove and exits the orbit through the infraorbital foramen as the infraorbital nerve.
It supplies sensory innervation to the skin of the lower eyelid, the side of the nose, part of the nasal septum, the cheek, and the upper lip. Now, let’s take a look at the zygomatic nerve, which travels to the lateral wall of the orbit.
It gives rise to the zygomaticofacial nerve, which supplies the skin over the zygomatic bone, and the zygomaticotemporal nerve, which supplies the skin of the anterior part of the temporal region.
Let’s move to the inferior division of the trigeminal nerve, called the mandibular nerve. This nerve supplies the skin of the posterior part of the temporal region, the skin anterior to the auricle, the skin over the body of the mandible, and the skin of the lower lip and the chin.
The mandibular nerve arises from the trigeminal ganglion and leaves the skull through the foramen ovale in the sphenoid bone.
It gives rise to three branches that innervate the skin of the face: the auriculotemporal nerve, the buccal nerve, and the inferior alveolar nerve.
The auriculotemporal nerve passes posterior to the mandible, deep to the parotid gland and emerges posterior to the temporomandibular joint.
It supplies the skin of the posterior part of the temporal region, the skin anterior to the auricle, and some parts of the external ear. The buccal nerve passes through the buccina tor muscle and supplies the skin of the cheek.
Finally, the inferior alveolar nerve passes through the mandibular foramen into the mandibular canal. Its terminal branch, called the mental nerve, exits the mandibular canal through the mental foramen and supplies the skin of the chin, the mandible, and the lower lip.
Cervical spinal nerves also provide a small part of the sensory innervation to the face, through the anterior and posterior rami of the C2 and C3 cervical spinal nerves.
The great auricular nerve arises from the anterior rami of C2 and C3 spinal nerves, and travels towards the face across the sternocleidomastoid muscle.
It provides sensory innervation to the skin of the angle of the mandible and the inferior part of the ear.
The lesser occipital nerve arises from the anterior ramus of the C2 spinal nerve, and travels along the posterior border of the sternocleidomastoid muscle.
It reaches the face posterior to the auricle and supplies the skin of the scalp posterior to the ear. The greater occipital nerve arises from the posterior ramus of the C2 spinal nerve and passes between the axis and the obliquus capitis inferior muscle.
It pierces the trapezius muscle and emerges to supply the skin of the occipital part of the scalp. The last branch is the third occipital nerve which arises from the posterior ramus of the C3 spinal nerve.
It pierces the trapezius muscle and travels to the occipital region to supply the skin of the lower occipital and the suboccipital regions.
Before we move on, let’s take a short break. Can you recall what area of the face is innervated by the maxillary nerve?
Now, motor innervation of the face is a bit more straightforward. All muscles of facial expression are innervated by the seventh cranial nerve, known as the facial nerve.
The facial nerve exits the cranium through the stylomastoid foramen, and provides a posterior auricular branch which innervates the auricularis posterior and occipital belly of the occipitofrontalis muscle.
It then travels anteriorly and enters the parotid gland, where it forms the parotid plexus. This plexus gives rise to the temporal, the zygomatic, the buccal, the marginal mandibular, and the cervical branches of the facial nerve.
Remember, To Zanzibar By Motor Car! The temporal branch runs across the zygomatic arch and innervates the frontal belly of the occipitofrontalis, corrugator supercilii, and the superior part of the orbicularis oculi muscle.
The zygomatic branch runs inferior to the eye and innervates the inferior part of the orbicularis oculi muscle and the muscles of the nose; procerus, nasalis and the levator labii superioris alaeque nasi.
The buccal branch runs horizontally and innervates the muscles of the upper lip, mouth and cheek, which are the risorius, levator anguli oris, zygomaticus major, zygomaticus minor, levator labii superioris, orbicularis oris,and the buccinator.
The marginal mandibular branch runs along the inferior border of the mandible and innervates the muscles of the lower lip and chin; the depressor anguli oris, depressor labii inferioris, and mentalis muscle. Lastly, the cervical branch travels posterior to the mandible and innervates the platysma.