Muscles of tongue( why you can't swallow the tongue itself?😂), arterial supply, venous and lymphatic drainage, nerve supply.

Tongue

It is a muscular organ, situated in floor of mouth, comprises voluntary skeletal muscle. It appears very mobile, still it cannot be swallowed like food, we will discuss about it later. It has 4 extrinsic & intrinsic muscle. Out of which 1 extrinsic muscle (palatoglossus) supplied by vagoaccesory complex. Remaining muscle supplied by hypoglossal nerve. In paralysis of hypoglossal nerve, on protrusion tip of the tongue deviates to paralysed side.

External features:

It has 

a. Root

b. Tip

c. Body (curved upper surface[dorsum] & inferior surface)

a) Root:

b) Tip of the tongue- forms the anterior free end which at rest, lies behind the upper incisor teeth.

c) Curved upper surface(dorsum)- divided into oral & pharyngeal parts.

    Inferior surface- confined to oral part only.

Dorsum of tongue:

Dorsum of tongue is convex in all direction, divides into two part oral & pharyngeal.

An oral part or anterior two thirds: 

• Also called papillary part of the tongue, placed on floor of the mouth. Margin contacts with the gums and teeth.
• In front of the palatoglossal arch, each margin shows a 4 to 5 vertical folds, called foliate papillae. 
• Superior surface of oral part covered with papillae which make it rough.
• Inferior surface is smooth and it shows a median fold called frenulum linguae.
• On either side of frenulum there is prominence produced by deep lingual vein.

The pharyngeal or lymphoid part of the tongue or posterior one-third: 

• Divides from anterior part of tongue by V shaped groove called sulcus terminalis. The meeting point of V called foramen caecum.
• The most posterior part called base of tongue, forms the anterior wall of the oropharynx.
• Mucous membrane has many lymphoid follicles, that collectively constitute lingual tonsil, it also contain mucous gland.

Papillae of the tongue:

Vallate or circumvallate papillae	Fungiform papillae	Filiform papillae or conical papillae	Foliate papillae
o   Larger in size and 8-12 in number. o   Situated in front of sulcus terminalis.	o   Numerous near the tip & margin of tongue. o   Some are scattered over the dorsum. o   Smaller than vallate papillae but larger than the filiform papillae. o   Bright red in color.	o   Covers presulcal area of the dorsum of tongue. o   It has characteristic velvety appearance. o   They are smallest and most numerous.	o   Few foliate are present.

Muscles of the tongue:

Middle fibrous septum divides the tongue into right and left halves. Each half contains 4 intrinsic and extrinsic muscles.

Intrinsic muscles	Extrinsic muscles
Superior longitudinal Inferior longitudinal Transverse Vertical	Genioglossus Hyoglossus Styloglossus Palatoglossus.

Intrinsic muscle: occupies the upper part of the tongue. Attached to submucous fibrous layer and to median fibrous septum. They alter the shape of tongue.

Intrinsic muscles	Location	Function
Superior longitudinal	Lies beneath the mucous membrane	Shortens the tongue makes the dorsum concave.
Inferior longitudinal	Lying close to inferior surface of tongue between the genioglossus & hyoglossus	Shortens the tongue makes the dorsum convex.
Transverse muscle	Extend from median septum to margin.	Makes tongue narrow and elongated.
Vertical muscle	Found at the border of anterior part of tongue	Makes tongue broad and flattened.

Extrinsic muscles: connect the tongue to the mandible via genioglossus: to the hyoid bone through hyoglossus: to the styloid process via styloglossus, and palate via palatoglossus.

Extrinsic muscle	Origin	Insertion	Action
Palatoglossus	Oral surface of palatine aponeurosis	Descends in palatoglossal arch to side of tongue	Pulls up the root of tongue, approximates the palatoglossal arches and thus closes the oropharyngeal isthmus.
Hyoglossus	Whole length of greater cornua and lateral part of hyoid bone	Side of tongue between styloglossus and inferior longitudinal muscle of tongue.	Depresses tongue, Makes dorsum convex, Retracts protruded tongue.
Styloglossus	Tip and part of anterior surface of styloid process	Into side of tongue	Pulls tongue upwards and backwards.
Genioglossus	Upper genial tubercle of mandible	Upper fibres into tip of tongue, middle fibres into dorsum, lower fibres into hyoid bone.	Retracts the tongue, Depresses the tongue, Pulls posterior part of tongue forwards and protrude the tongue forwards. Life- saving muscle.

Arterial supply of tongue:

Derived from tortuous lingual artery a branch of external carotid artery.

The root of the tongue supplied by tonsillar, a branch of facial artery, and ascending pharyngeal, branch of external carotid.

Venous drainage:

Two venae comitantes accompany the lingual artery and one vena comitantes accompanies the hypoglossal nerve.

The deep lingual vein -

• The largest and principle vein of the tongue.
• Course: visible on inferior surface of the tongue, runs backwards and crosses the genioglossus and hyoglossus below the hypoglossal nerve.

Lymphatic drainage:

Tip of the tongue	Drains bilaterally to the submental nodes.
Right & left half of remaining anterior 2/3rd	Unilaterally to submandibular nodes.
Posterior one-third	Bilaterally to the jugulo-omohyoid nodes[lymph node of tongue].
Posterior most part	Bilaterally into upper deep cervical lymph nodes.

Nerve supply:

Motor nerves:

All intrinsic and extrinsic muscles (except the palatoglossus) supplied by hypoglossal nerve.

The palatoglossus supplied by cranial root of accesory nerve through the pharyngeal plexus. 

Sensory nerves:

Nerve supply	Anterior two-third	Posterior one-third	Posterior most or vallecula
Sensory	Lingual nerve (post-trematic branch of 1st arch)	Glossopharyngeal	Internal laryngeal branch of vagus.
Taste	Chorda tympani except vallate papillae (pretrematic branch of 1st arch)	Glossopharyngeal including the vallate papillae	Internal laryngeal branch of vagus.
Development of epithelium from endoderm	Lingual swellings of 1st arch	Third arch which forms large ventral part of hypobranchial eminence	Fourth arch which forms small dorsal part of hypobranchial eminence

We have seen about muscles, arterial supply, venous and lymphatic drainage and nerve supply in this part. We will see about histology, development, taste pathway and clinical anatomy in another article.

[Let me know in the comment section, if you want me to upload any other topic]