Anatomy of the facial nerve (CN VII)

Humans can make thousands of expressions with their faces, and this is possible thanks to the 7th cranial nerve, also known as the facial nerve.

The facial nerve does much more than just control our facial expressions though, it also plays an important role in salivating, sensation for some parts of the skin, and it’s even involved in the perception of taste!

The facial nerve has many functions including somatic sensory, special sensory, branchial motor, and visceral or parasympathetic motor innervation.

Parasympathetic innervation travels with the facial nerve to glands such as the lacrimal glands, nasal glands, palatal mucosal, and submandibular and sublingual salivary glands.

It provides special sensory innervation to the anterior two thirds of the tongue; as well as somatic sensory innervation for a small portion of skin at the ear and external tympanic membrane.

Now, where did the facial nerve come from? The facial nerve actually originates from a structure that begins to appear when we are about the size of a poppy seed, known as the second pharyngeal arch.

Remember, the pharyngeal arches are 6 embryological structures, of which only 5 eventually develop into the muscles, arteries, bones and cartilage of the head and neck.

Many structures are derived from the second pharyngeal arch, such as the lesser horn of the hyoid bone, the styloid process, the stylohyoid ligament, and the stapes.

Importantly, the stylohyoid muscle, the posterior belly of the digastric muscle, the stapedius muscle and the muscles of facial expression are also derived from the second arch, which means they are all innervated by the facial nerve.