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Tongue

Tuesday, June 24, 2014

Tongue

The tongue is a muscular organ situated in the floor of the mouth. It is associated with the functions of

taste,speech,mastication and deglutition. It has an oral part that lies in the mouth,and a pharyngeal

part that lies in the pharynx. The oral and pharyngael parts are separated by a V-shaped sulcus,the

sulcus terminalis

Tongue comprises skeletal muscle which is voluntary.These voluntary muscles start behaving as

involuntary in any classroom-funny?

Thanks to the taste buds that the multiple hotels, restaurants, fast food outlets,chat-pakori shops,etc.

are flourishing. One need not be too fussy about the taste of the food. Nutritionally, it should be

balanced and hygienic.

"Tongue is barely three inches long, but it can kill a person six feet tall." Tongue appears very

mobile, still it cannot be swallowed like food, because tongue is anchored to hyoid

bone,mandible,styloid process and soft palate. Four intrinsic and three extrinsic muscles of tongue are

supplied by hypoglossal nerve. Only palatoglossus is supplied by vagoaccessory complex. In paralysis of

hypoglossal nerve, the tip of tongue if protruded gets deviated to the paralysed side.

The tongue has:

1. A root,

2. A tip,and

3. A body,which has:

A curved upper surface or dorsum.

An inferior surface

INTRODUCTION

EXTERNAL FEATURES

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Tongue

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The dorsum of the tongue,epiglottis and palatine tonsil.

The dorsum is divided into oral and pharyngeal parts. 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 two

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 divided into:

An oral part or anterior two-thirds.

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 forwared up to the palatoglossal arches. The foramen

caecum represents the site from which the hhyroid diverticulum grows down in thge embryo. The oral

and pharyngeal parts of the tongue differ in their development, topography, structure, and function.

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 forwared 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 surafce, 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 posteriormost 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

fold. On either side of the median fold, there is a depression called the vallecula. The lateral folds

separate the vallecula from piriform fossa.

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The inferior surface of tongue and the floor of the mouth.

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.

PAPILLAE OF THE TONGUE

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 are raised above

the surface

2. The fungoform 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 iis pointed and covered with keratin; the apex is often

split into filamentous processes.

4. foliate papillae-few foliate papillae are also present.

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papilla of tongue

A middle fibrous septum divides the tongue into right and left halves. Each half contains four intrinsic

and four extrinsic muscles

Intrinsic Muscles

1. Superior longitudinal.

2. Inferior longitudinal.

3. Transverse.

4. Vertical.

Extrinsic Muscles

1. Genioglossus.

2. Hyoglossus.

3. Styloglossus.

4. Palatoglossus.

The intrinsic muscle 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. It shortens the tongue and makes its dorsum

concave.

The inferior longitudinal muscle is a narrow band lying close to the inferior surface of the tongue

betwwen the geniglossus and the hyoglossus. It shortens the tongue and makes its dorsum convex.

The transverse muscle extends from the median septum to the margins. it makes the tongue narrow

and elongated. The vertical muscle is found at the borders of the anterior part of the tongue. It makes

the tongue broad and flattened.

The extrinsic muscles connect the tongue to the mandible via genioglossus; to hyoid bone through

hyoglossus; to the styloid process via styloglossus, and the palate via palatoglossus.

Intrinsic muscles of Tongue

MUSCLES OF THE TONGUE

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Intrinsic muscles of Tongue

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Extrinsic muscles of Tongue

Muscle of tongue

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Extrinsic muscle of tongue

1. Muscle- Palatoglossus

Origin- Oral surface of palatine aponeurosis

Insertion- Descends in the palatoglossal arch to the side od tongue at the junction of oral and

pharyngeal parts

Action- Pulls up the root of tongue

2. Muscle- Hyoglossus

Origin- whole length of greater cornua and lateral part of hyoid bone

Insertion- Side of tongue betwwen styloglossus and inferior longitudinal muscle of tongue

Action- Depresses Tongue, Makes dorsum convex.

3. Muscle-Styloglossus

Origin- Tip and part of anterior surface of styloid process

Insertion- Into the side of tongue

Action- pulls tongue upwards and backwards

4. Muscle-Genioglossus(Fan shaped bulky muscle)

Origin- Upper genial tubercle of mandible

Insertion- Upper fibers into the tip of tongue. Middle fibres into the dorsum. Lower fibres

into the hyoid bone

Action- Retracts the tongue.Depresses the tongue.Pulls the posterior part of tongue.It is life

saving muscle

It is derived from the tortuous lingual artery a branch of the external carotid artery. The root thye

tongue is also supplied by the tonsillar a branch of facial artery, and ascending pharyngeal barnch of

external carotid.

The arrangement of the vena comitantes/veins of the tongue is variable. Two venae comitantes

ARTERIAL SUPPLY OF TONGUE

VENOUS DRAINAGE

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accompany the lingual artery, and one vena comitantes accompanies the hypoglossal nerve. The deep

lingual vein is the largest and principle vein of the tongue. It is visible on the inferior surface of the

tongue. It runs backwards and cross 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

1. The tip of the tongue drains bilaterally to the submental nodes.

2. The anterior two-thirds of the tongue drain unilaterally to the submandibular nodes.

3. The posterior one-thirds of the tongue drains bilaterally to the jugulo-omohyoid nodes.

4. The posterior most part of the tongue drains bilaterally into the upper deep cervical lymph

nodes.

lYMPHATIC DRAINAGE

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Lymphatic drainage of tongue

Motor Nerves 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 nerves

The lingual nerves is the nerve of genral sensation and the chorda tympani is the

nerve of taste for the anterior two-thirds of the except vallate papillae.

The glossopharyngeal nerve is the nerve for both genral sensation and taste for the posterior

one-third of the tongue including the circumvallate papillae. The posterior most part of the tongue is

supplied by the vagus nerve through the internal laryngeal branch.

Nerve supply- Sensory

Anterior two-thirds-lingual

posterior one-third-Glossopharyngeal

posterior most part or vallecula- Internal laryngael branch of vagus

Nerve supply- Taste

Anterior two-thirds- Chorda tympani except vallate papillae

Posterior one-third- Glossopharyngeal including the vallate papillae

Posterior most part or vallecula- Internal laryngeal branch of vagus

NERVE SUPPLY

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Nerve supply of tongue

1. The bulk of the tongue is made up of striated muscles.

2. The mucous membrane consists os a layer of connective tissue 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 lymphoid follicles. 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 vallate papillae, and on the walls of the

surrounding sulci. taste buds are numerous over the foliate papillae and over the posterior one -

thirds of tongue; and sparsely distributed on the fungiform papillae,the soft palate,the epiglottis

and the pharynx. there are no taste buds on the mid-dorsal region of the oral part of the tongue.

1. Epithelium

Anterior two-thirds: From two lingual swellings and one tuberculum impar, which arise from

the first branchial arch. The tuberculum impar soon disappears.therfor, it is supplied by

lingual nerve and chorda tympani

Posterior one-third: From the third arch Therefore,it is supplied by the glossopharyngeal

nerve.

posterior most part from the fourth arch. This is therefore supplied by the vagus nerve.

2. Muscles

The muscles develop fromn the occipital myotomes which are supplied by the hypoglossal

nerve

3. Connective Tissue

The connective tissue develops from the local mesenchyme

HISTOLOGY

DEVELOPMENT OF TONGUE

TASTE PATHWAY

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Posted by amin dubaliya at 11:50 PM

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 tractus

solitarius in the medulla.

Taste from posterior one-third of tongue including the vallate papillae is carried by cranial

nerve 9 th till the inferior ganglion. The central processe also reach the tractus solitarius

Taste from posterior most part of tongue and epiglottis travels through vagus nerve till the

inferior ganglion of vagus. These central processes also also reach tractus solitarius.

After a relay in tractus solitarius, the solitariothalamic tract is formed which becomes a part

of trigeminal lemniscus and reaches posteroventromedial nucleus of thalamus of the opposite

side. Another relay here takes them to lowest part of postcentral gyrus, which is the area for

taste.

Taste pathway

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