The tongue has:

1. Root
2. Tip
3. Body

1. Root

• Root is a fixed part.
• It is attached:

Between the mandible and hyoid bones, it is related to:

• Geniohyoid muscle
• Mylohyoid muscle

2. Tip

• Tip forms the anterior free end of the tongue.
• At rest, it lies behind the upper incisor teeth.

3. Body

The body has:

1. A curved upper surface → dorsum
2. An inferior surface → confined to the oral part only

Dorsum of tongue is convex in all directions.

It is divided into:

1. Oral part / anterior two-thirds
2. Pharyngeal part / posterior one-third

The two parts are separated by a faint V-shaped groove → sulcus terminalis.

The two limbs of the V meet at a median pit called the foramen caecum.

Foramen Caecum

Represents the site from which the thyroid diverticulum grows down in the embryo.

Oral and pharyngeal parts of tongue differ in:

• Development
• Topography
• Structure
• Function

• Placed on the floor of the mouth.
• Its margins are free and are in contact with:

• Gums
• Teeth

Just in front of the circumvallate papillae, each margin shows 4–5 vertical folds called foliate papillae.

Superior Surface

• Shows a median furrow.
• Is covered with papillae.
• Papillae make it rough.

Inferior Surface

• Covered with a smooth mucous membrane.
• Shows a median fold called frenulum linguae.

On either side of the frenulum:

• A prominence is produced by the deep lingual veins.

More laterally:

• A fold called plica fimbriata is present.
• It is directed forwards and medially towards the tip of tongue.

• Lies behind:
• Palatoglossal arches
• Sulcus terminalis

Its posterior surface is sometimes called the base of the tongue.

It forms the anterior wall of the oropharynx.

Mucous Membrane

• Has no papillae.
• Contains many lymphoid follicles.

These lymphoid follicles collectively constitute the lingual tonsil.

Mucous glands are also present.

Posteromost Part

The posteriormost part of the tongue is connected to the epiglottis by three folds of mucous membrane:

1. Median glossoepiglottic fold
2. Right lateral glossoepiglottic fold
3. Left lateral glossoepiglottic fold

On either side of the median fold there is a depression called the vallecula.

The lateral folds separate the vallecula from the piriform fossa.

Glossitis

• Glossitis is usually a part of generalized ulceration of the mouth cavity or stomatitis.
• In certain anaemias, the tongue becomes smooth due to atrophy of the filiform papillae.

Swelling in Acute Glossitis

Tongue contains:

• A rich network of lymphatics
• Loose areolar tissue

These are responsible for enormous swelling of the tongue in acute glossitis.

Tongue fills the mouth cavity and then protrudes out of it.

Observation of Jaundice

Undersurface of tongue is a good site, along with the bulbar conjunctiva, for observation of jaundice.

Tongue in Unconscious Patients

In unconscious patients, tongue may fall backwards and obstruct the air passages.

This can be prevented by:

1. Lying the patient on one side with head down → “tonsil position”
2. Keeping the tongue out mechanically.

Lingual Tonsil

Lingual tonsil in the posterior one-third of tongue forms part of Waldeyer’s ring.

Papillae of Tongue

Papillae are projections of mucous membrane or corium.

They give roughness to the anterior two-thirds of the tongue.

There are four types:

1. Vallate / circumvallate
2. Fungiform
3. Filiform / conical
4. Foliate

1. Vallate / Circumvallate Papillae

• Large in size.
• Diameter → 1–2 mm.
• Number → 8–12.
• Situated immediately in front of the sulcus terminalis.
• Each papilla is a cylindrical projection.
• It is surrounded by a circular sulcus.
• Walls of the papilla have taste buds.

2. Fungiform Papillae

Numerous near:

• Tip of tongue
• Margins of tongue

Some are also scattered over the dorsum.

• Smaller than vallate papillae but larger than filiform papillae.
• Each papilla consists of:

• Narrow pedicle
• Large rounded head

• Distinguished by their bright red colour.
• Contain apical taste buds.

3. Filiform / Conical Papillae

• Cover the presulcal area of the dorsum of tongue.
• Give the tongue a characteristic velvety appearance.
• They are the smallest and most numerous of the lingual papillae.
• Each is pointed and covered with keratin.
• Apex is often split into filamentous processes.
• No taste buds.

4. Foliate Papillae

• Present at the lateral border, just in front of circumvallate papillae.
• They are leaf-shaped.
• They are rudimentary and have no taste buds.

A middle fibrous septum divides the tongue into right and left halves.

Each half contains:

• 4 intrinsic muscles
• 4 extrinsic muscles

Intrinsic Muscles

1. Superior longitudinal
2. Inferior longitudinal
3. Transverse
4. Vertical

Extrinsic Muscles

1. Genioglossus
2. Hyoglossus
3. Styloglossus
4. Palatoglossus

Intrinsic Muscles

Intrinsic muscles occupy the upper part of the tongue.

They are attached to:

• Submucous fibrous layer
• Median fibrous septum

They alter the shape of the tongue.

1. Superior Longitudinal

2. Inferior Longitudinal

3. Transverse

4. Vertical

Extrinsic Muscles

Extrinsic muscles connect the tongue to:

• Mandible → via genioglossus
• Hyoid bone → through hyoglossus
• Styloid process → via styloglossus
• Palate → via palatoglossus

Actions of Extrinsic Muscles

Palatoglossus

• Pulls up the root of tongue.
• Approximates the palatoglossal arches.
• Thus closes the oropharyngeal isthmus.

Hyoglossus

• Depresses tongue.
• Makes dorsum convex.
• Retracts the protruded tongue.

Styloglossus

• Pulls tongue upwards and backwards.
• Thus retracts the tongue.

Genioglossus

• Retracts the tongue.
• Depresses the tongue.
• Pulls the posterior part of tongue forwards and protrudes the tongue.
• It is a life-saving muscle.

Arterial supply is derived from the tortuous lingual artery, a branch of the external carotid artery.

Supply of Root of Tongue

• Tonsillar artery → branch of facial artery
• Ascending pharyngeal branch of external carotid artery

Arteries Identified

• Lingual artery
• Dorsal lingual arteries
• Deep lingual artery
• Facial artery
• Ascending pharyngeal artery
• Tonsillar branch of facial artery
• External carotid artery

1. Deep Lingual Vein

• Chief vein of tongue.
• Seen on the inferior surface of tongue near the median plane.

2. Venae Comitantes

• Accompany the lingual artery.
• They are joined by dorsal lingual veins.

Formation of Lingual Vein

These veins unite at the posterior border of hyoglossus.

They form the lingual vein.

Lingual vein ends in the internal jugular vein.

Lymphatic drainage of tongue is divided into 3 main regions:

1. Marginal vessels
2. Central vessels
3. Dorsal vessels

1. Marginal Vessels

Drain the marginal area of anterior part of tongue.

Tip of Tongue and Lingual Frenulum

Lymphatics drain bilaterally into:

• Submental nodes
• Submandibular nodes
• Jugulo-omohyoid nodes

Rest of Margin of Tongue

Lymphatics drain into:

• Submandibular nodes
• Digastric nodes

2. Central Vessels

Drain the central region of the anterior two-thirds of tongue.

Drain into:

• Jugulodigastric nodes
• Submandibular nodes

3. Dorsal Vessels

Drain:

• Circumvallate papillae
• Posterior one-third of tongue

Drain into:

• Jugulo-omohyoid nodes
• Jugulodigastric nodes

Motor Nerves

All muscles of tongue, intrinsic and extrinsic, are supplied by the hypoglossal nerve, except palatoglossus.

Palatoglossus is supplied by the cranial root of accessory nerve via pharyngeal plexus.

Sensory Supply

1. Anterior Two-thirds

Without circumvallate papillae:

2. Posterior One-third

With circumvallate papillae:

• Both general and special sensation are carried by the glossopharyngeal nerve.

3. Posterior-most Part

• Supplied by the internal laryngeal branch of superior laryngeal nerve.
• Superior laryngeal nerve is a branch of the vagus nerve.

It leaves the cranial cavity through the anterior condylar / hypoglossal canal.

Course

1. Lies between:
   • Internal jugular vein
   • Internal carotid artery
2. It lies in front of the vagus.
3. Lower down, it curves forwards and crosses:
   • Internal carotid artery
   • External carotid artery
4. It also crosses the loop of the lingual artery to lie on the hyoglossus muscle.
5. Finally, it enters the substance of tongue.

Supply

Supplies:

• 3 extrinsic muscles
• All 4 intrinsic muscles of tongue.

Sorbitrate

Sorbitrate is taken sublingually for immediate relief from angina pectoris.

It is absorbed fast because of:

• Rich blood supply of tongue
• Bypassing of portal circulation

Genioglossus — Safety Muscle of Tongue

Genioglossus is called the “safety muscle of the tongue”.

If it is paralysed:

• Tongue falls back on the oropharynx.
• Air passage becomes blocked.

During anaesthesia, tongue is pulled forwards to clear the air passage.

Genioglossus and Hypoglossal Nerve Testing

Genioglossus is the only muscle of the tongue that protrudes it forwards.

It is used for testing the integrity of the hypoglossal nerve.

If the right hypoglossal nerve is paralysed:

• On protrusion, tongue deviates to the right side.

Normal left genioglossus:

• Pulls the base to the left side.
• Apex gets pushed to the right side.

Apex and base lie at opposite ends.