The tongue is a muscular organ situated in the floor of the mouth. It is associated with the functions of
(i) taste,
(ii) speech,
(iii) chewing, and
(iv) deglutition.
PARTS
The tongue has:
- A root,
- A tip, and
- A body, which has:
- A curved upper surface or dorsum
- An inferior surface.
The dorsum is divided into oral and pharyngeal parts by a V-shaped, the sulcus terminalis.
The inferior surface is confined to the oral part only.
The root is attached to the styloid process and soft palate above, and to mandible and the hyoid bone below.
Because of these attachments, we are not able to swallow the tongue itself.
In between the mandible and hyoid bones, it is related to the geniohyoid and mylohyoid muscles.
The tip of the tongue forms the anterior free end which, at rest, lies behind the upper incisor teeth.
The dorsum of the tongue is convex in all directions.
It is divided into
1. An oral part or anterior two-thirds.
2. A pharyngeal part or posterior one-third,
by a faint V-shaped groove, the sulcus terminalis. The two limbs of the 'V' meet at a median pit, named the foramen caecum.
They run laterally and forwards up to the palatoglossal arches.
The foramen caecum represents the site from which the thyroid diverticulum grows down in the embryo. The oral and pharyngeal parts of the tongue differ in their development, topography, structure, and function
3. Small posterior most part
The oral or papillary part of the tongue is placed on the floor of the mouth.
Its margins are free and in contact with the gums and teeth.
Just in front of the palatoglossal arch, each margin shows 4 to 5 vertical folds, named the foliate papillae. The superior surface of the oral part shows a median furrow and is covered with papillae which make it rough.
The inferior surface is covered with a smooth mucous membrane, which shows a median fold called the frenulum linguae.
On either side of the frenulum, there is a prominence produced by the deep lingual veins.
More laterally there is a fold called the plica fimbriata that is directed forwards and medially towards the tip of the tongue
The pharyngeal or lymphoid part of the tongue lies behind the palatoglossal arches and the sulcus terminalis.
Its posterior surface, sometimes called the base of the tongue, forms the anterior wall of the oropharynx.
The mucous membrane has no papillae,
but has many lymphoid follicles that collectively constitute the lingual tonsil.
Mucous glands are also present.
The posterior most part of the tongue is connected to the epiglottis by three-folds of mucous membrane.
These are the median glossoepiglottic fold and the right and left lateral glossoepiglottic folds.
On either side of the median fold, there is a depression called the vallecula
The lateral folds separate the vallecula from the piriform fossa.
PAPILLAE OF THE TONGUE
• These are projections of mucous membrane or corium which give the anterior two-thirds of the tongue its characteristic roughness.
• These are of the following three types.
1. Vallate or circumvallate papillae;
• They are large in size 1-2 mm in diameter and
• are 8-12 in number.
• They are situated immediately in front of the sulcus terminalis.
- Each papilla is a cylindrical projection surrounded by a circular
sulcus. - The walls of the papilla have taste buds.
2. The fungiform papillae are numerous near the tip and margins of the tongue, but some of them are also scattered over the dorsum.
- These are smaller than the vallate papillae but larger than the
filiform papillae. - Each papilla consists of a narrow pedicle and a large rounded
head. - They are distinguished by their bright red colour.
3. The filiform papillae or conical papillae cover the presulcal area of the dorsum of the tongue, and
- give it a characteristic velvety appearance.
- They are the smallest and most numerous of the lingual
papillae. - Each is pointed and covered with keratin; the apex is often split
into filamentous processes.
4. Few foliate papillae are also present.
MUSCLES OF THE TONGUE
• A middle fibrous septum divides the tongue into right and left halves.
• Each half contains four intrinsic and four extrinsic muscles. lntrinsic Muscles
- Superior longitudinal
- Inferior longitudinal
- Transverse
- Vertical.
• The intrinsic muscles occupy the upper part of the tongue,
and are attached to the submucous fibrous layer and to the median fibrous septum.
- They alter the shape of the tongue.
- The superior longitudinal muscle lies beneath the mucous membrane.
- The inferior longitudinal muscle is a narrow band lying close to the inferior surface of the tongue between the genioglossus and the hyoglossus.
- The transverse muscle extends from the median septum to the margins.
- The vertical muscle is found at the borders of the anterior part of the tongue
Extrinsic Muscles
- Genioglossus
- Hyoglossus
- Styloglossus
- Palatoglossus
The extrinsic muscles connect the tongue to the mandible via genioglossus;
to the hyoid bone through hyoglossus;
to the styloid process via styloglossus, and
to the palate via palatoglossus
Palatoglossus
Origin - Oral surface of palatine aponeurosis
Insertion-
Descends in the palatoglossal arch to the side of tongue at the junction of oral and pharyngeal parts
Nerve supply - the cranial root of the accessory nerve through the pharyngeal plexus.
Action - Pulls up the root of tongue, approximates the palatoglossal arches and thus closes the oropharyngeal isthmus
Hyoglossus
Origin - Whole length of greater cornua and lateral part of hyoid bone
Insertion - Side of tongue between styloglossus and inferior longitudinal muscle of tongue
Nerve Supply - Hypoglossal Nerve
Action - Depresses tongue, makes dorsum convex, retracts the protruded tongue
Styloglossus
Origin - Tip and part of anterior surface of styloid process
Insertion - lnto the side of tongue
Nerve Supply - Hypoglossal Nerve
Action - Pulls tongue upwards and back wards, i.e. retracts the tongue
Genioglossus
fan shaped bulky muscle
Origin - Upper genial tubercle of mandible
Insertion-
Upper fibres into the tip of tongue
Middle fibres into the dorsum
Lower fibres into the hyoid bone
Nerve Supply - Hypoglossal Nerve
Action -
upper fibres - Retracts the tongue
middle fibres - Depresses the tongue
lower fibres - Pulls the posterior part of tongue forwards and protrude the tongue forwards.
It is a life-saving muscle ( Safety muscle of the tongue )
Arterial Supply of Tongue
It is derived from the tortuous lingual artery a branch of the external carotid artery.
The root of the tongue is also supplied by the tonsillar artery a branch of facial artery, and ascending pharyngeal branch of external carotid
Venous Drainage
The arrangement of the vena comitantes/veins of the tongue is variable.
Two venae comitantes accompany the lingual artery, and one vena comitant accompanies the hypoglossal nerve.
The deep lingual vein is the largest and principal vein of the tongue.
It is visible on the inferior surface of the tongue. It runs backwards and crosses the genioglossus and the hyoglossus below the hypoglossal nerve.
These veins unite at the posterior border of the hyoglossus to form the lingual vein which ends in the internal jugular vein.
Lymphatic Drainage
1. The tip of the tongue drains bilaterally to the submental nodes.
2 .The right and left halves of the remaining part of the anterior two-thirds of the tongue drain unilaterally to the submandibular nodes.
A few central lymphatics drain bilaterally to the deep cervical nodes.
3. The posteriormost part and posterior one third of the tongue drain bilaterally into the upper deep cervical lymph nodes including jugulodigastric nodes.
4. The whole lymph finally drains to the jugulo- omohyoid nodes. These are known as the lymph nodes of the tongue.
Nerve Supply
Motor Supply
All the intrinsic and extrinsic muscles, except the palatoglossus, are supplied by the hypoglossal nerve.
The palatoglossus is supplied by the cranial root of the accessory nerve through the pharyngeal plexus.
Sensory Supply
The lingual nerve is the nerve of general sensation and the chorda tympani is the nerve of taste for the anterior two-thirds of the tongue except vallate papillae
The glossopharyngeal nerve is the nerve for both general sensation and taste for the posterior one- third of the tongue including the circumvallate papillae.
The posteriormost part of the tongue is supplied by the vagus nerve through the internal laryngeal branch
Carcinoma of the tongue is quite common. The affected side of the tongue is removed surgically.
All the deep cervical lymph nodes are also removed, i.e. block dissection of neck because recurrence of malignant disease occurs in lymph nodes.
Carcinoma of the posterior one-third of the tongue is more dangerous due to bilateral lymphatic spread.
Sorbitrate is taken sublingually for immediate relief from angina pectoris. It is absorbed fast because of rich blood supply of the tongue and bypassing of portal circulation.
Genioglossus is called the 'safety muscle of the tongue, because if it is paralysed, the tongue will fall back on the oropharynx and block the air passage.
During anaesthesia, the tongue is pulled forwards to clear the air passage.
Genioglossus is the only muscle of the tongue which protrudes it forwards.
It is used for testing the integrity of hypoglossal nerve.
If hypoglossal nerve of right side is paralysed, the tongue on protrusion will deviate to the right side.
Normal Ieft genioglossus will pull the base to left side and apex will get pushed to right side.
Histology :
The bulk of the tongue is made up of striated muscles.
2. The mucous membrane consists of a layer of connective tissue (corium), lined by stratified squamous
epithelium.
On the oral part of the dorsum, it is thin, forms papillae, and is adherent to the muscles.
On the pharyngeal part of the dorsum, it is very rich in
On the inferior surface, it is thin and smooth.
Numerous glands, both mucous and serous lie deep to the mucous membrane.
3. Taste buds are most numerous on the sides of the circumvallate papillae, and on the walls of the surrounding sulci.
Taste buds are numerous over the foliate papillae and over the posterior one-third of the tongue; and sparsely distributed on the fungiform papillae, the soft palate, the epiglottis and the pharynx.
There are no taste buds on the middorsal region of the oral part of the tongue.
Development :
Epithelium
I. Anterior two-thirds: From two lingual swellings, which arise from the first branchial arch.
Therefore, it is supplied by lingual nerve (post trematic) of 1st arch and chorda tympani (pre trematic) of 2nd arch.
2. Posterior one-third: From cranial large part of the hypobranchial eminence,
Therefore, it is supplied nerve. i.e. from the third arch. by the glossopharyngeal
3. Posteriormost part - from the fourth arch. This is supplied by the vagus nerve.
Muscles
The muscles develop from the occipital myotomes which are supplied by the hypoglossal nerve.
Connective Tissue
The connective tissue develops from the local mesenchyme.
Taste Pathway
1. The taste from anterior two-thirds of tongue except from vallate papillae is carried by chorda tympani branch of facial till the geniculate ganglion.
The central processes go to the tractus solitarius in the medulla.
2. Taste from posterior one-third of tongue including the circumvallate papillae is carried by cranial nerve IX till the inferior ganglion.
The central processes also reach the tractus solitarius 3. Taste from posteriormost part of tongue and epiglottis travels through vagusnetve till the inferior ganglion of vagus.
These central processes also reach tractus solitarius.
4. After a relay in tractus solitarius, the solitario-thalamic tract is formed which becomes a part of trigeminal lemniscus and
reaches postero-ventromedial nucleus of thalamus of the opposite side. Another relay here takes them to lowest part of postcentral gyrus, which is the area for taste.
Clinical Anatomy
Injury to any part of the pathway causes abnormality in appreciation of taste.
Referred pain is felt in the ear in diseases of posterior part of the tongue, as ninth and tenth nerves are common supply to both the regions.
Watch lectures on YouTube:
The Tongue | Parts| Features| Papillae| Muscles |Nerve & Blood supply|Lymphatic Drainage|Development
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