Tongue

 Tongue

EXTERNAL FEATURES

-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, (iv)deglutition, and

(v) cleansing of mouth.

-The tongue has:

(1) A root :- attached to the styloid process and soft palate above,and to mandible and the hyoid bone below.

(2) A tip :-it is free end , lies behind the upper incisor teeth at rest.

(3) A body:- has:

a. A curved upper surface(dorsum)

b. An inferior surface:

-dorsum of the tongue is convex in all

directions , and contains following

(1)oral part

(2) pharyngeal part

(3)Small posteriormost part

**oral part and pharyngeal part is divided V-shaped groove called sulcus terminalis. The two limbs of the 'V' meet at a median pit called foramen caecum. foramen

caecum is the site from which the thyroid diverticulum grows down in the embryo.

(1)The oral or papillary part of the tongue:-

*It is placed on the floor of the mouth. Its margins are free and in contact with the gums and teeth.

*its superior surface is covered with papillae which make it rough.

* inferior surface is covered with a smooth mucous membrane, its has median fold called frenulum linguae.On either side of the frenulum,there is deep Lingual veins. More laterally there is a fold called the plica fimbriata.

(2)The pharyngeal or lymphoid part of the tongue:-

*It lies behind palatoglossal arches and sulcus terminalis.

*it forms the anaterior walls of oropharynx.

*It has no papillae, but has many lymphoid follicles that collectively

constitute the lingual tonsil.

* Mucous glands are also present.

(3) The posteriormost part:-

*It 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 vallecula. Lateral folds separate vallecula from piriform fossa.

CLINICAL ANATOMY

(*##*#*clinical anatomy maa point ali dere xa .. jun tapi lai samjhna sajilo hunx ..tyo matra 2-4 ota lekhe hunxa... na bhye sape lekhe ni hunx*#* )

-Glossitis is generalized ulceration of mouth cavity.

-Due to presence of a rich network of lymphatics, in acute glossitis , swelling of tongue occure and fills up the mouth cavity.

- undersurface of the tongue is a good site along with the bulbar conjunctiva for observation of jaundice.

-Lingual tonsil forms part of Waldeyer's ring.

-in certain anaemias, the tongue becomes smooth due to atrophy of the filiform papillae.

-In unconscious patients, the tongue may fall back and obstruct the air passages, in such case tongue should kept out mechanically or patients should lyed with head down (the 'tonsil position').

PAPILLAE OF THE TONGUE

-These are projections of mucous membrane. Found in anterior two-thirds of the tongue.

- These are of the following types:-

(1) Vallnte or circumvallate papilla:-

* they are large, 8-12 in number.

* situated immediately in front of the sulcus terminalis.

* Each papilla is a cylindrical projection. surrounded by a circular sulcus.

(2) The fungiform papillae:-

*they are numerous, they are smaller than the vallate papillae but larger than the filiform papillae.

* near the tip and margins of the tongue. some are also scattered over the dorsum.

* Each papilla consists of a narrow pedicle and a large rounded head.

*they have bright red colour.

(3)filiform papillae or conical papillae:-

*smallest and most numerous

* found in presulcal area of the dorsum.

* Each papillae is pointed and covered with keratin.

(4)Foliate papillae:-

* they are present at the lateral border just infront of circumvallate papillae. *They are leaf shaped.

MUSCLES OF THE TONGUE

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

four extrinsic muscles.

#Intrinsic Muscles:-

*present within tongue

*its function is to alter the shape of the

tongue.

 (1) Superior longitudinal:

 *It arises from fibrous tissue deep to the dorsum

 *it inserts into the overlying mucous membrane near root.

 *they pass longitudinally back from tip to root superiorly.

 *they elevate the tip and sides of tongue superiorly.

 *they makes dorsum concavity and shortens the tongue.

(2)Inferior longitudinal:

*It arises from the fibrous

tissue beneath the mucous membrane

*it insert into mucous membrane of dorsum.

*they pass longitudinal back from tip to root and to hyoid bone inferiorly.

*they curl the tip of the tongue inferiorly.

*they makes the dorsum convex and shortens the tongue.

(3)Transverse:

*arises at the fibrous lingual septum *insert into the submucous fibrous tissue at the lateral margins of the tongue.

*it lies on as sheet on either side of midline, deep to the siperior longitudinal muscles.

*they narrow the tongue.

(4)Vertical:

*it lies at borders of the anterior part of tongue.

*it makes the tongue broad.

#Extrinsic Muscles

(1)Genioglossus :

*they connect tongue to mandible

*Protrudes the tongue

(2) Hyoglossus :

*they connect tongue to hyoid bone.

*Depresses the tongue

(3)Styloglossus :

*they connect tongue to styloid process

*Retracts the tongue

(4)Palatoglossus :

*they connect tongue to palate.

*Elevattes the tongue

Arterial Supply of Tongue

-Tongue is supplied by Lingual artery, which is a branch of External carotid artery.

-Root of tongue is also supplied by Tonsillar artery (a barnch of facial artery) and Ascending pharynheal branch (of external carotid artery).

Venous Drainage

-Two venae cornitantes accompany

the lingual artery

-one vena comitant accompanies

the hypoglossal nerve

-deep lingual vein is the

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

-all these veins unite to form a Lingual vein which ends in the Internal jugular vein.

Lymphatic Drainage

-Tip of the tongue drains bilaterally to the submental nodes .

-remaining part of anterior two-thirds of the tongue drain unilaterally to submandibular nodes.

-posteriormost part, posterior one-third of the tongue, and few central lymphatics drain bilaterally into Upper deep cervical lymph nodes .

*All lymph finally drains to the Jugulo-omohyoid nodes. It is known as Lymph nodes of the tongue.

Nerve Supply

#Motor Nerves

-Seven muscles of tongue is supplied by

hypoglossal nerve(XII).

-Only palatoglossus is supplied by vago accessory complex.

#Sensory Nerves

-anterior two-thirds of the tongue except vallate papillae :

*for general sensation - Lingual nerve

*for taste - Chorda tympani

-posterior one-third of the tongue including the circurnvallate

papillae : supplied by Glossopharyngeal nerve

-posteriormost part : supplied by Vagus nerve.

CLINICAL ANATOMY

-Carcinoma of the tongue is quite common. The affected side of the tongue is removed surgically.

-Sorbitrate is taken sublingually for immediate relief from angina pectoris.

-Genioglossus is called the safety muscle of the tongue, And is the only muscle of the tongue which protrudes it forwards.

-if hypoglossal nerve of right side is paralysed, tip of the tongue is deviate to the right side.

HISTOLOGY

-it has striated muscles.

-mucous membrane is linned by stratified squamous epithelium.

-oral part of dorsum has papillae, pharyngeal part of dorsum has Lymphoid follicles. And inferior surface is smooth.

-Taste buds are most nemerous in Circumvallate papillae and Foliate papillae , and sparsely present on fungiform papaillae.

*taste buds are not present on Mid-dorsal region of oral part of tongue.

*Structure of Taste buds:It has two types of cells

(a) Sustentacular or Supporting cells:they are spindle shaped .

(b) Gustatory cells: they are long slender and centrally placed.

DEVELOPMENT OF TONGUE

Epithelium

-Anterior two-thirds: develop from First branchial arch.

-Posterior one-third: develop from third arch.

-Posteriormost part :develop from fourth arch.

Muscles

-develop from the occipital myotomes, thus called Skeletal muscles.

Connective Tissue

- it develops from local mesenchyme.

TASTE PATHWAY

-Chorda tympani(VII) from anterior two-thirds, IX nerve from posterior one-third , And Vagus nerve(X) from posteriormost part reach to Tractus solitarius.

-relay from tractus solitarius through solitario-thalamic tarct reaches to Postero-ventromedial nucleus of thalmus. From there it reaches to Postcentral gyrus of cerebral cortex(the area for taste).

CLINICAL ANATOMY

-Injury to any part of the pathway causes abnormality in appreciation of tast.

-Referred pain is felt in the ear in diseases of posterior part of the tongue.

THE END

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