Anatomy of taste

Anatomy

Innervation

Chorda Tympani- This is a special branch of the facial nerve (cranial nerve 7) that arises from the taste buds of the anterior two thirds of the tongue (anterior to the sulcus terminalis). The facial nerve leaves the cranial vault through the internal auditory meatus along with the vestibulocochlear nerve and runs in the facial canal. Next it passes between the malleus and the incus which are two of the ossicles found in the middle ear. This is reflected in the name of the nerve as it makes a chord with the tympanic membrane, hence chorda tympani. It emerges from the petrotympanic fissure, and then emerges from the cranial cavity to enter the infratemporal fossa. At this point, the nerve converges with a division of V3, the mandibular division of the trigeminal nerve in order to reach the submandibular ganglion as the lingual nerve. It is then distributed to the taste buds of the anterior two thirds of the tongue with the branches of the lingual nerve that provide general sensation to the surface of the tongue.

Glossopharyngeal nerve- Taste and sensation of the posterior one third of the tongue is provided by the glossopharyngeal nerve (cranial nerve 9). The nerve leaves the skull through the jugular foramen along with the vagus nerve (cranial nerve 10) and the accessory nerve (cranial nerve 11).

Vagus Nerve- The epiglottis also has a small amount of taste sensation, which is conveyed by the vagus nerve (cranial nerve 10).

The taste buds provide sensation, which is passed to the caudal and rostral regions of the nucleus tractus solitarius in the medulla. From the gustatory parts of the medulla, the information next projects to the ventroposterior medial thalamus. From this nucleus, the information is sent to the primary gustatory cortex that is located in the insular cortex.

Blood supply

The lingual artery perfuses the tongue, and is the second branch of the external carotid artery. The tongue is drained by the lingual veins, which drain into the internal jugular veins.

Salivary glands

Saliva has an important role in chewing, swallowing and taste. The three glands that secrete saliva into the mouth are located around the face.

Submandibular- Under the angle of mandible, these glands are innervated by the facial nerve via the submandibular ganglion and are perfused by the submental arteries (branches of the facial artery). They secrete saliva in the sublingual space through the submandibular ducts or Wharton’s ducts.

Sublingual- They are innervated by the facial nerve and perfused by the sublingual (lingual artery) and submental (facial artery) arteries. They empty their secretions into the floor of the mouth via a collection of ducts referred to as ducts of Rivinus.

Parotid Gland- This is a large gland that sits on the side of the face, anterior and inferior to the ear. The motor branches of the facial nerve (temporal, zygomatic, buccal, mandibular and cervical) run through it. Innervation is from the glossopharyngeal nerve via the otic ganglion. The parotid duct (Stenson’s duct) enters the mouth by the cheek, opposite the second upper molar. The gland is perfused by branches of the external carotid artery.