The Tongue

 The Tongue    

The tongue is a mass of striated muscle covered with mucous membrane. The muscles attach the tongue to the styloid process and the soft palate above and to the mandible and the hyoid bone below.

The tongue is divided into right and left halves by a median fibrous septum.

 Mucous Membrane of the Tongue

The mucous membrane of the upper surface of the tongue can be divided into anterior and posterior parts by a V-shaped sulcus, the sulcus terminalis. The apex of the sulcus projects backward and is marked by a small pit, the foramen cecum.

The sulcus serves to divide the tongue into two parts-

·        the anterior two thirds, or oral part

·        the posterior third or pharyngeal part

The foramen cecum is an embryologic remnant and marks the site of the upper end of the thyroglossal duct.

Papillae

Three types of papillae are present on the upper surface of the anterior two thirds of the tongue:

·        Filiform Papillae

·        Fungiform Papillae

·        Circumvallate Papillae

On the posterior one third and lateral side of tongue foliate papillae are present.

The mucous membrane covering the posterior third of the tongue is devoid of papillae but has an irregular surface caused by the presence of underlying lymph nodules, the lingual tonsil.

The mucous membrane on the inferior surface of the tongue is reflected from the tongue to the floor of the mouth.

In the midline anteriorly, the undersurface of the tongue is connected to the floor of the mouth by a fold of mucous membrane, the frenulum of the tongue.

On the lateral side of the frenulum, the deep lingual vein can be seen through the mucous membrane.

Lateral to the lingual vein, the mucous membrane forms a fringed fold called the plica fimbriata.

Muscles of the Tongue

The muscles of the tongue are divided into two types: intrinsic and extrinsic.

Intrinsic Muscles- These muscles are confined to the tongue and are not attached to bone. They consist of longitudinal, transverse, and vertical fibers.

Nerve supply- Hypoglossal nerve

Action- Alter the shape of the tongue

Extrinsic Muscles- These muscles are attached to bones and the soft palate. They are the

·        Genioglossus

·        Hyoglossus

·        Styloglossus

·        Palatoglossus

Nerve supply- Hypoglossal

Blood Supply- The lingual artery, the tonsillar branch of the facial artery and the ascending pharyngeal artery supply the tongue. The veins drain into the internal jugular vein.

Sensory Innervation of tongue

Anterior two thirds- Lingual nerve branch of mandibular division of trigeminal nerve (general sensation) and chorda tympani branch of the facial nerve (taste)

Posterior third: Glossopharyngeal nerve (general sensation and taste)

Movements of the Tongue

Protrusion: The genioglossus muscles on both sides acting together

Retraction- Styloglossus and hyoglossus muscles on both sides acting together Depression- Hyoglossus muscles on both sides acting together

Retraction and elevation of the posterior third: Styloglossus and palatoglossus muscles on both sides acting together

Shape changes- Intrinsic muscles