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

Trigeminal nerve(part-4) : Mandibular division, origin, course, branches.

 Mandibular division:

Largest branch of the trigeminal nerve.

Mixed nerve with two roots: a large sensory root & smaller motor root.

Origin of roots:

Sensory root: origins at inferior angle of trigeminal ganglion.

Motor root: arises in motor cells located in pons and medulla oblongata.

Area innervated by mandibular division includes as follows:

Sensory root	Motor root
a.Skin Temporal region Auricular External auditory meatus Cheek Lower lip Lower part of face(chin region) b.Mucous membrane: Cheek Tongue (anterior two thirds) Mastoid cells c. Mandibular teeth and periodontal tissue. d. Bone of mandible e. Temporomandibular joint f. Parotid gland.	a. Masticatory muscles. Masseter Temporalis Pterygoideus medialis Pterygoideus lateralis b. Mylohyoid c. Anterior belly of the digastric. d. Tensor tympani. e. Tensor veli palatini.

Branches:

It gives off branches in three area: Undivided nerve, anterior and posterior division.

Undivided nerve	Divided nerve
a. Nervus spinosus b. Nerve to medial pterygoid muscle.	a. anterior division:  nerve to the lateral pterygoid muscle  masseter muscle, temporal muscle, buccal nerve. b. posterior division: auriculotemporal nerve Lingual nerve Mylohyoid nerve Inferior alveolar nerve:dental branches Incisive branch: dental branches. Mental nerve.

Undivided nerve:

It gives off two branches.

1. Nervous spinosus.[meningeal branch of mandibular nerve]
2. Medial pterygoid nerve.

Nervous spinosus:

Enters cranium through foramen spinosum along with middle meningeal artery to supply the duramater & mastoid air cells.

Medial pterygoid nerve: 

It is motor nerve to medial(internal) pteygoid muscle.

Supply motor branch to tensor vali palatini & tensor tympani.

Anterior division:

Branches of these will provide- 

• Motor innervation to muscles of mastication.
• Sensory innervation to mucous membrane cheek & buccal mucous membrane of mandibular molar.

Anterior division smaller than posterior division.

Course: 

Under lateral pterygoid, it gives off several branches:

👉Deep temporal nerve [ to temporal muscle ]

👉Masseter nerve.

👉Lateral pterygoid nerve.

Buccal nerve:

Also known as buccinator nerve and long buccal nerve, usually passes between two heads of lateral pterygoid to reach external surface of muscle.

It then follows inferior part of temporal muscle & emerges under the anterior border of masseter muscle, continuing in anterolateral direction.

At level of occlusal plane of mandiblular 3rd  or 2nd molar, it crosses in front of anterior border of ramus, & enters the cheek through buccinator muscle.[here sensory fibre distributes to skin of cheek].

Other fibre passes into retromolar triangle, providing sensory innervation to buccal gingiva of mandibular molars & mucobuccal fold in that region.

Posterior division:

Primarily sensory with small motor component.

It descends for short distance downward & medially to lateral pterygoid muscle, at which point it branches into:

• Auriculotemporal nerve
• Lingual nerve
• Inferior alveolar nerve.

Auriculotemporal nerve:

Traverse the upper part of parotid gland & crosses posterior portion of zygomatic arch.

⧭ All of its branches are sensory.

⧭Provides sensory fibre to skin over the area of innervation of motor branches of facial nerve:

Zygomatic, buccal, mandibular- communicates with otic ganglion, providing sensory, secretory & vasomotor fibre to the parotid gland.

Anterior auricular branches- supply skin over helix and tragus of ears.

Branches to external auditory meatus- innervating skin over meatus & tympanic membrane.

Articular branches- to posterior portion of TMJ.

Superficial temporal- supply skin over temporal region.

Lingual nerve:

2nd branch of posterior division.

Course: 

• Passes downward medial to the lateral pterygoid muscle, lies between ramus & medial pterygoid muscle in pterygomandibular space.
• Runs anterior & medial to inferior alveolar nerve.
• Continues downward & forward deep to pterygomandibular raphae, below attachment of superior constrictor of pharynx, to reach side of base of tongue slightly below and behind mandibular 3rd molar.[here it lies just below mucous membrane in the lateral lingual sulcus].
• It then proceeds anteriorly across muscle of tongue, looping downward & medial to submandibular (wharton's) duct to deep surface of sublingual gland where it breaks up into its terminal branches.

Supplies: sensory tract to anterior 2\3rd of tongue.

Provide both general sensation & gustation (taste) to this region.

It also provide sensory innervation to mucous membrane of floor of mouth & gingiva on the lingual side of mandible.

Inferior alveolar nerve:

Largest branch of mandibular division.

Course: Descends medial to lateral pterygoid muscle & lateroposterior to lingual nerve, to the region between sphenomandibular ligament & medial surface of mandibular ramus, it enters mandibular canal at the level of mandibular foramen.

Throughout its path, it is accompanied by inferior alveolar artery & vein.

Nerve, artery and vein travels anteriorly in mandibular canal, towards mental foramen, it divides into terminal branches- Incisive nerve, & mental nerve.

Mylohyoid nerve:

Mixed nerve, branch from Inferior Alveolar Nerve.

Before entry into mandibular canal - It runs downward & forward in mylohyoid groove on medial surface of ramus, and along body of mandible to reach mylohyoid muscle.

• Motor divison- mylohyoid muscle & anterior belly of digastric muscle.
• Sensory- skin on inferior & anterior surface of mental protuberance, mandibular incisor.

Mylohyoid also invloved in pulpal innervation of mesial root of mandibular 1st molar.

Incisive nerve:

Remains within mandibular canal, for nerve plexus that innervate pulpal tissue of mandibular 1st premolar, canine, incisors via dental branches.

Mental nerve:

Exit canal, through mental foramen, & divides into 3 branches- innervate skin of chin, skin & mucous membrane of lip.

Trigeminal nerve(part-3): Maxillary division, origin, and branches.

 Maxillary branch arises from middle of trigeminal ganglion and purely sensory in function.

Origin:

➤Leaves cranium through foramen rotundum. [Foramen rotundum located in greater wing of the sphenoid bone]

➤Crosses pterygopalatine fossa gives off branches to - sphenopalatine ganglion, posterior superior alveolar nerve, zygomatic branches.

➤Enters orbit through inferior orbital fissure, occupies infraorbital groove & becomes the infraorbital nerve, which course anteriorly into infraorbital canal.

➤Emerges on anterior surface of the face, through infraorbital foramen- divides into terminal branches, supplying skin of face, nose, lower eyelid, upper lip.

Branches:

Trigeminal nerve (part-2) - Ophthalmic division course, distribution, branches.

 Abstract:

Ophthalmic division is first branch of trigeminal nerve. Purely sensory in nature. Travels anteriorly in lateral wall of cavernous sinus to the medial part of superior orbital fissure, through which it exits the skull into the orbit. Before passing through superior orbital fissure it divides into three branches- lacrimal, frontal, nasociliary.

Course & Relation:

Arises - medial part of convex anterior border of the trigeminal ganglion.

Pierces- duramater of trigeminal cave.

Enters- lateral wall of cavernous sinus, where it lies below trochlear nerve.

            

Enters orbit through superior orbital fissure by dividing into 3 branches:

Branches:

Lacrimal branch: 

Course- runs along lateral wall of the orbit along with lacrimal artery and end in lacrimal gland.

Supplies- lacrimal gland & conjunctiva.

Pierces- orbital septum to supply the lateral part of skin of upper eyelid.

Frontal branch:

Course:- runs forward between levator palpebral superioris and periosteum lining the roof of the orbit.

In middle of orbit it divides into - large supraorbital & small supratrochlear nerve.

👉 Supraorbital nerve:  Frontal air sinus, upper eyelid, forehead, scalp till vertex.

👉Supratrochlear nerve: upper eyelid, conjunctiva, lower part of forehead.

Nasociliary branch:

💨 Runs forward and medially crossing optic nerve from above.

💨 Runs from lateral to medial side behind the ophthalmic artery.

💨 On reaching the medial wall of the orbit, it ends by dividing into anterior ethmoidal and infratrochlear nerves.

Branches:

a)Anterior ethmoidal nerve: supplies- middle and anterior ethmoidal sinus, medial internal nasal, lateral internal nasal, external nasal- skin of ala of vestibule and tip of nose.

Course of anterior ethmoidal nerve:

In nasal cavity- it lies in groove on posterior surface of nasal bone, gives internal nasal branches to nasal septum & lateral wall of nose.

At lower border of nasal bone, the nerve leaves nasal cavity & appears on dorsum of nose as external nasal nerve.

b)Infratrochlear nerve: both eyelid, side of nose, lacrimal sac.

c) Sensory root to ciliary ganglion- given just before crossing optic nerve.

d) Long ciliary nerve: arise from nasociliary nerve, as it crosses the optic nerve, pass forward enter eyeball supply sensory fibres to ciliary body, iris, cornea. It also carry some postganglionic sympathetic fibres to dilator pupillae.

e) Posterior ethmoid nerve: enters posterior ethmoid foramen, supplies ethmoidal & sphenoidal air sinus.

Clinical anatomy: When ophthalmic nerve paralysed, ocular conjunctiva becomes insensitive to touch.

Trigeminal nerve (part 1): overview of branches, motor & sensory root, and ganglion.

 INTRODUCTION:

• Largest cranial nerve.
• Consist of large sensory and small motor root.
• Motor root- supplies muscles of mastication.
• Sensory root- supplies skin of entire face, mucous membrane of cranial viscera and oral cavity.(except pharynx and base of tongue)

Motor root:

Sensory root:

It comprise central processes of ganglion cells located in trigeminal (semilunar or gasserian) ganglion.

Three sensory division: 

• Ophthalmic division
• maxillary division
• mandibular division.
  
  
  
  
  
  

Gasserian or semilunar ganglion:

1. Two ganglia, one innervating two side of face.
2. Location: Meckel's cavity, on the anterior surface of petrous portion of the temporal bone.
   
   
   
3. They are flat & cresent shaped, apprx 1*2cm.
4. Convexities faces anteriorly and downward.
5. Sensory fibre enter concave portion of each cresent.
6. Three sensory divisions( ophthalmic, maxillary, mandible) exit from convexity.

Ophthalmic division:

• First branch, sensory in nature, smallest of three branches.
• Exits the cranium, enters orbit through superior orbital fissure(SOF).
• Nerve trunk supplies eyeball, conjunctiva, lacrimal gland, parts of mucous membrane of nose and paranasal sinus, skin of forehead, eyelid and nose.

Before ophthalmic nerve passes through the SOF it divides into three branches.

Maxillary division:

Arises from middle of trigeminal ganglion. Purely sensory.

Leaves the cranium through foramen rotundum.

Mandibular division:

• Largest branch of trigeminal nerve.
• Mixed in nature, contains both sensory(large) and motor(small).
• Two roots emerges from cranium through foramen ovale.

Branches: gives off branches in three area, undivided, anterior and posterior(divided nerve).

Undivided nerve	Divided nerve
Nervus spinosus  Nerve to medial pterygoid muscle.	a. anterior division:  nerve to the lateral pterygoid muscle, masseter muscle, temporal muscle, buccal nerve. b. posterior division: auriculotemporal nerve Lingual nerve Mylohyoid nerve Inferior alveolar nerve:dental branches Incisive branch: dental branches. Mental nerve.

Commentary: The above content covers short description of trigeminal nerve divisions and their branches.

In our subsequent blogs detailed notes of each branch will be discussed.

Kindly report in comment section if you have any doubts or if you find any error.