MRCS Part B (OSCE) - Online Resources

The tongue is attached to the hyoid bone and mandible.

The muscles of the tongue are broadly divided into extrinsic and intrinsic muscles. In general, extrinsic muscles help in the movements of the tongue (elevation,depression, retraction and protrusion) and intrinsic muscles alter the shape of the
tongue (by lengthening and shortening, curling and uncurling, flattening and rounding).

The extrinsic muscles of the tongue are:
 Genioglossus : Protrusion
 Hyoglossus : Depression
 Styloglossus : Elevation and retraction
 Palatoglossus : Depression of the soft palate and elevation of the back of the tongue

The intrinsic muscles of the tongue are:
 Superior longitudinal
 Inferior longitudinal
 Transverse muscles
 Vertical muscles

The motor supply of the muscles of the tongue is by the hypoglossal (XII) nerve except for palatoglossus, which is supplied by the pharyngeal plexus

Anterior 2/3rd of the tongue:
 General sensation (touch and temperature): Lingual nerve (branch of V3)
 Taste sensation: Chorda Tympani (branch of VII)
Posterior 1/3rd of the tongue:
 General sensation: Glossopharyngeal nerve
 Taste sensation: Glossopharyngeal nerve

There are five taste sensations on the tongue: 1. Sweet : Tip of tongue 2. Salt : Lateral margins of tongue 3. Sour : Posterior part of the tongue 4. Bitter : Posterior part of the tongue 5: Umami (savoury taste) : All regions of the tongue

The primary arterial supply of the tongue derives from the lingual artery, which is a branch of the external carotid artery. There is also a secondary blood supply to the tongue from the tonsillar branch of the facial artery and ascending pharyngeal artery.

There are four types of papillae: 1. Vallate papillae : Anterior to the terminal sulcus 2. Foliate Papillae : Lingual mucosa 3. Filiform papillae : Parallel to the terminal sulcus 4. Fungiform papillae : Apex of the tongue

The development of the tongue can be divided into an anterior 2/3rd and posterior 1/3rd as well as into development of the mucosa and muscle. The mucosa of the anterior 2/3rd of the tongue develops from the 1st pharyngeal arch. The posterior
1/3rd is mainly from the 3rd and 4th pharyngeal arches.
Mucosa of the anterior 2/3rd of the tongue: Develops during 4th week of intrauterine life from a median tongue bud, the tuberculum impar, that unites with two lateral lingual swellings during the 5th week. Their line of fusion from right and
left is marked by the median sulcus.
Mucosa of the posterior 1/3rd of the tongue: In the 4th week, a swelling appears from the 2nd pharyngeal arch, in the midline, called the copula. During the 5th and 6th weeks, the copula is overgrown by a swelling from the 3rd and 4th arches called
the hypopharyngeal eminence (has got a cranial part and caudal part). The posterior 1/3rd of tongue develops from the cranial part of the hypopharyngeal eminence and the caudal part form the most posterior part of the tongue (epiglottis and adjacent regions).
The boundary between the two parts of the tongue is marked by the 'V' shaped terminal sulcus. At the tip of the terminal sulcus is the foramen caecum, which is the point where the embryological thyroid begins to descend.
Muscles of the tongue: The occipital myotomes migrate to the floor of the developing oral cavity and form the intrinsic and extrinsic muscles of the tongue.