By Chandan Sekhon - Medicine Student @ Peterhouse, Cambridge
The tongue is located in the floor of the oral cavity and is connected to the palate via the palatoglossus and palatopharyngeus muscles, along with the pharynx. Its nerve supply is divided into two, with the anterior (front) two-thirds being supplied by the chorda tympani branch of the facial nerve. This nerve mediates taste from the region and is, therefore, a sensory nerve. The lingual nerve is a sensory nerve originating from the mandibular nerve, from the trigeminal nerve. This mediates general sensation from the region. The posterior (back) third is supplied by the glossopharyngeal nerve, serving both taste and general sensation. The division between the two regions is by a region called the sulcus terminalis and regions called circumvallate papillae, which are supplied by the glossopharyngeal nerve. The root of the tongue is supplied by the vagus nerve. The front two-thirds of the tongue is covered by small projections called papillae, which have taste buds at their base.
Muscles of the tongue:
The muscles of the tongue can be divided into intrinsic and extrinsic muscles with the intrinsic muscles altering the shape of the tongue, and the extrinsic muscles changing the position of the tongue. Some of the extrinsic muscles include the genioglossus (this is attached to the anterior part of the mandible, pulling the tongue forward), hyoglossus (this is attached to the hyoid bone, pulling tongue downwards and retracts it) and styloglossus (this is attached to styloid process and retracts and elevates the tongue)
How the tongue develops in the embryo:
The tongue begins development in the 4th week of gestation and is derived from occipital somites. In the first stage of development, lingual and medial swellings appear:
2 lateral lingual swellings – This contributes to the mucosa of the anterior 2/3 of the tongue.
3 medial swellings: - Tuberculum impar – This contributes to the mucosa of the anterior 2/3 of the tongue. - Cupola – This forms the mucosa of the posterior 1/3 of the tongue. - Epiglottal swelling – This forms the epiglottis.
During the 4th week, the lateral lingual swellings overgrow the tuberculum impar and merge together – forming the mucosa of the anterior 2/3 of the tongue. Their line of fusion is marked by the central groove of the tongue. The anterior 2/3 and posterior 1/3 fuse, forming a V-shaped groove known as the terminal sulcus. As the tongue forms, it is initially tethered to the floor of the oral cavity. A process of carefully programmed cell death known as sculpting apoptosis releases the tongue, leaving in place the lingual frenulum to anchor the tongue in the mouth.
Further reading:
This is an interesting article about a condition called tongue-tie where the tongue is tethered too strongly to the base of the mouth. It details the causes and symptoms of this: https://www.mayoclinic.org/diseases-conditions/tongue-tie/symptoms-causes/syc-20378452
This article outlines some common medical diseases associated with the tongue so is an interesting read: https://www.webmd.com/oral-health/picture-of-the-tongue
A much more detailed and comprehensive outline of the anatomy of the tongue, so quite difficult, but interesting nonetheless: https://www.kenhub.com/en/library/anatomy/tongue
This study explores the link between the Human Papilloma Virus (HPV) and the incidence of tongue cancer. Quite a complex study with some difficult terms, but definitely an interesting study: https://onlinelibrary.wiley.com/doi/full/10.1002/ijc.24994