Sample chapter nerves of the orbit-title anatomy for dental students by as moni

� Optic, oculomotor, trochlear and abducent nerves

� Ophthalmic nerve and its branches

� Ciliary ganglion

LEARNING OBJECTIVES

CHAPTER 23

Nerves of the Orbit

OPTIC NERVE (II CRANIAL NERVE)

Th e optic nerve may be considered as a tract rather than a nerve. It has more than one million nerve fi bres.Development. Optic stalk—a diverticulum from the fl oor of the diencephalon.Commencement. It commences from the central processes of the ganglionated cell layer of retina.Course. Fibres of the optic nerve fi bres pierce the choroid and sclera. It emerges through the lamina cribrosa. Th is is situated 3 mm medial to central pole of back of the sclera. Th e nerve then passes through the retrobulbar compartment of the orbit. It enters the optic canal through the optic foramen and reaches the anterior cranial fossa.Termination. It joins the nerve of the opposite side to form the optic chiasma.Length of optic nerve. About 40 mm.

Parts of Optic Nerve

1. Intraorbital part about 25 mm long. 2. Part within the optic canal about 5 mm long. 3. Intracranial part about 10 mm long. 4. Within the orbit the nerve is about 25 mm long.

Relations in the orbit (Fig. 23.1)Th e nerve is longer than the space. So it is tortuous and is surrounded by orbital pad of fat and muscles of the eyeball.

Eyeball

Medialrectus

Naso-ciliarynerve

Lateralrectus

Ciliaryganglion

Figure 23.1. Relations of the optic nerve in the orbit (nasociliary nerve crosses the optic nerve superiorly)

Th e nerve is crossed superiorly from the lateral to medial side by the following structures:

Ophthalmic vein �

Ophthalmic artery �

Nasociliary nerve �

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CHAPTER 23 � NERVES OF THE ORBIT 193

Relations (Figs. 23.2, 23.3):Laterally. � Ciliary ganglion. Lateral rectus muscle. Medially. � Medial rectus muscle. Th e central artery of retina pierces the optic nerve about 1 cm behind the eyeball. Th e artery enters the retina and supplies it. It is an end artery. Obstruction of this artery causes blindness.Posteriorly. � Within the orbit, the nerve is surrounded by the origin of recti muscles called ‘cone of muscles.’Inferiorly. � Nerve to medial rectus.

Relations within the optic canal (Fig. 23.4)Length � —About 5 mm.Inferiorly and laterally. � Ophthalmic artery.Medially. � Sphenoidal air sinus and posterior ethmoidal air sinuses.

Intracranial part

Length. About 10 mm.Relations:

Superior. � Anterior cerebral artery.Posterior. � Hypophysis cerebri.Lateral. � Internal carotid artery.

Blood supply:Central artery of retina. �

Superior hypophyseal artery. �

Ophthalmic artery. �

Posterior ciliary artery. �

Venous drainage. Central vein of retina. It drains into cav-ernous sinus. Other veins of the nerve accompany the arteries supplying it.

Structure (Fig. 23.5)

Optic nerve is covered by dura, arachnoid and pia �

maters.Th e pia mater surrounding the nerve enters into the nerve �

as septulae.Th e septulae divide the nerve into many compartments. �

Subarachnoid space surrounding the brain continues to �

cover the optic nerve.In the centre of the nerve, the central artery and vein of �

retina are situated.

Figure 23.2. Relations of optic nerve near optic foramen

Eyeball

Optic nerve

Ciliary ganglion

Anteriorethmoidalnerve

Long ciliary nerve

Posteriorethmoidalnerve

Communicatingbranch to ciliaryganglion

Nasociliary nerve

Infratrochlearnerve

Figure 23.3. Relations of optic nerve and nasociliary nerve

Posteriorethmoidalartery

Central arteryof retina

Optic nerve

Ophthalmic artery

Posteriorciliary artery

Lacrimalartery

Anteriorethmoidalartery

Internal carotid

Eyeball

Figure 23.4. Relations of the ophthalmic artery with optic nerve


SECTION II � HEAD AND NECK194

Applied Anatomy

• Infection from the brain and meninges may spread to the optic nerve.

• Infections from the ethmoidal and sphenoidal air sinuses may spread to the optic nerve.

• Injury to one optic nerve results in complete loss of vision on that side.

• When intracranial pressure is increased, the optic nerve head in the retina is swollen. This is called papilloedema.

• An aneurysm of the internal carotid artery or anterior cerebral artery may compress the optic nerve.

• When both optic nerves are injured, there is complete loss of vision.

Optic Chiasma

Optic chiasma is the anterior part of anatomical hypothalamus. It lies anterior to interpeduncular fossa.Situation. It is situated posterosuperior to the chiasmatic sulcus. Th e superior surface of the chiasma is connected to rostrum of the corpus callosum by the lamina terminalis.

Th e hypophysis cerebri and the diaphragma sella are found posteroinferior to the chiasma.Formation. Decussation of optic nerves of both sides.Arrangement of fi bres in the chiasma. Fibres from the nasal side of the retina cross and go to the opposite side of optic tract. Th is crossing is found in the centre of the optic chiasma.

Fibres from the temporal side of the retina does not cross in the chiasma, but runs into the same side of the tract.Blood supply:

Anterior cerebral artery �

Anterior choroidal artery �

Anterior communicating artery �

Middle cerebral artery �

Optic Tract

Commencement. From the optic chiasma, it commences lateral to the tuber cinereum.Course. It passes posteriorly and laterally. It encircles the cerebral peduncle.Termination. It terminates by dividing into medial and lateral parts. Th e signifi cance of the medial part is not known well. Th e lateral part synapses in the lateral geniculate body. From here fresh fi bres originate as optic radiation. Th e optic radiation terminates in the occipital cortex. Few fi bres from the lateral part of the optic tract join the superior colliculus of midbrain and pretectal nucleus. Th ese fi bres are essential for light refl ex activity of the pupil. Some fi bres of the lateral part of the optic tract may terminate in the hypothalamus. Th ey may be connected to the pineal gland.Arrangement of fi bres within the optic tract. Th ese fi bres are arranged in three groups:

Dorsolateral �

Ventrolateral �

Ventromedial �

Th e dorsolateral side of the tract contains fi bres from the macula. Th e ventrolateral side of the tract contains fi bres from the lower lateral quadrant of retina. Th e ventromedial side of the tract has fi bres from upper part of retina.Blood supply:

Anterior choroidal artery �

Middle cerebral artery �

Posterior communicating artery �

Internal carotid artery �

Injury to Various Parts of Optic Pathway

1. When one optic nerve is injured completely, the following clinical features are manifested:

Total blindness on the aff ected eye. �

Accommodation refl ex remains normal. �

2. Injury to the midline of optic chiasma—bitemporal hemianopia—loss of lateral fi elds of vision.

3. Compression on the lateral sides of optic chiasma— binasal hemianopia.

4. Involvement of optic tract, e.g. right side—right hom-onymous hemianopia—loss of temporal vision on the right eye and medial vision on the left eye.

5. Lesion of visual cortex above the calcarine sulcus. It produces lower quadrantic hemianopia.

Th e upper quadrantic hemianopia is due to partial lesion of visual cortex below the calcarine sulcus.

6. Foster Kennedy syndrome—lesion of orbital surface of frontal lobe. Ipsilateral blindness, anosmia and contralateralpapilloedema.

7. Tay–Sachs disease. Usually Jewish people are aff ected by this familiar disorder:

Figure 23.5. Structure of optic nerve



Mental illness �

Blindness �

Reddish spotted macula lutea �

Atrophy of the eyeball �

8. Scotoma. Abnormal blind spots in the visual fi eld:Positive scotoma. � Patient complains of a dark spot in vision.Negative scotoma. � Dark spot exists in vision but unnoticed by the patient.Motile scotoma. � Vitreous body may show opaque bodies. Th ey produce visual defects.Absolute scotoma � . Loss of perception of light.Central scotoma � . Central visual fi eld is lost.Scintillating scotoma. � Th e patient gets coloured light rays or silvery bright rays in the visual fi eld.

Visual Pathway

Visual receptors (rods and cones)

Bipolar cells (primary neurons)

Ganglionated cells (secondary neurons)

Optic nerve

Optic chiasma

Nasal fi bres cross and temporal fi bres do not cross

Optic tract

Lateral geniculate body (tertiary neuron)

Optic radiation

Visual area in the occipital cortex (area 17)

Visual interpretation is given at visuopsychic area

OCULOMOTOR NERVE (Fig. 23.6)(III CRANIAL NERVE)

Th e oculomotor nerve is the third cranial nerve. It has motor and parasympathetic functions.

General somatic eff erents of the oculomotor nerve supply extraocular muscles except superior oblique and lateral rectus. Visceromotor fi bres of the oculomotor nerve are the pregan-glionic parasympathetic fi bres from the Edinger-Westphal nucleus to supply the sphincter pupillae.

Nucleus

It is situated within the upper part of midbrain. Th e nucleus is found in the ventral part of periaqueductal grey.

Parts of the nucleus and muscles supplied (Table 23.1)

Table 23.1 Parts of the nucleus and muscles supplied

No. Name of nucleus Muscle supplies

1. Dorsal nucleus Inferior rectus muscle

2. Ventral nucleus Superior rectus muscle

3. Intermediate nucleus Inferior oblique muscle

4. Ventromedial nucleus Medial rectus muscle

5. Caudal central Levator palpebrae superioris

6. Edinger-Westphal nucleus Sphincter pupillae and ciliaris muscles

Red nucleus

Oculomotornucleus

Oculomotornerve

Periaqueductal grey

Cerebral aqueduct

Cerebral peduncle

Substantia nigra

Figure 23.6. Oculomotor nerve

Figure 23.7. Interpeduncular fossa showing emergence of the oculomotor nerve



Figure 23.8. Oculomotor nerve—vascular relations

Connections of the nucleusCorticonuclear tract. � Connects the oculomotor nucleus with motor areas of both cerebral hemispheres.Medial longitudinal bundle. � Connects the 3rd nerve nucleus with 4th, 6th and 8th cranial nerve nuclei.Pretectal nucleus of both sides. � It is necessary for consen-sual pupillary refl exes.Tectobulbar tract. � It connects the nucleus with the supe-rior colliculus, which in turn is connected to the occipital cortex.

Course

Th e nerve commences from its nuclear complex and passes forwards within the tegmentum of the midbrain. It pierces the red nucleus and substantia nigra. It leaves the midbrain medial to the cerebral peduncle.

Th e nerve enters the interpeduncular fossa (Fig. 23.7). It passes between the posterior cerebral and superior cerebellar arteries (Fig. 23.8). Here it lies medial to the trochlear nerve (Fig. 23.9). Th e nerve is then situated lateral to the posterior communicating artery.

It runs forwards and laterally and enters the oculomotor triangle (between free and attached borders of the tentorium cerebelli). It crosses the roof of the cavernous sinus and enters the lateral wall of the sinus.

Figure 23.9. Vascular relations of oculomotor and trochlear nerves.

Relations in the Lateral Wall of the Cavernous Sinus (Fig. 23.10)

In the lateral wall of the cavernous sinus, the nerve is situated superior to:

Trochlear nerve (IV) �

Ophthalmic nerve (V � 1)Maxillary nerve (V � 2)

Figure 23.10 Relations of oculomotor nerve

Sphenoidal sinusCavernous sinus

Maxillary nerve

Pituitary gland

Oculomotor nerve

Trochlear nerve

Ophthalmic nerve

Abducentnerve

Internalcarotidartery



Near the anterior end of the cavernous sinus, the nerve divides into superior and inferior divisions (Fig. 23.11). Th ey enter the orbit through the superior orbital fi ssure.

Th ey pass within the common tendinous ring. In between the superior and inferior divisions, the nasociliary nerve is situated.Superior division. Th is division is situated above and lateral to the optic nerve. It supplies levator palpebrae superioris and superior rectus muscle.Inferior division. It supplies:

Medial rectus muscle �

Inferior rectus muscle �

Inferior oblique muscle �

Communications (Fig. 23.12)

Internal carotid plexus of nerves �

Ophthalmic nerve (V � 1)Ciliary ganglion �

Th e Edinger-Westphal nucleus sends parasympathetic fi bres into the oculomotor nerve.

Light refl ex pathway (pupilloconstrictor pathway)


Optic nerve

Optic chiasma

Optic tract

Pretectal nucleus (midbrain)

Edinger-Westphal nucleus of both sides

Oculomotor nerve

Inferior division of oculomotor nerve

Ciliary ganglion

Short ciliary nerves

Sphincter pupillae and ciliaris muscles

When light is focused on one eye, there is bilateral pupillary constriction. Th is is because the optic tract of one side is con-nected to the pretectal nuclei of both sides. Th is connection is done by the posterior commissure.

Pupillodilator pathway


Optic nerve

Optic chiasma

Optic tract

Tegmentum of midbrain

Reticular formation of pons and medulla

Lateral horn cells of T1 and T2 segments

White rami communicantes

Sympathetic trunk

Superior cervical ganglion

Internal carotid plexus

Sympathetic plexus around ophthalmic artery

Ciliary ganglion

Dilator pupillae muscle of the eye

Medial rectus

Superior rectus

Levator palpebraesuperioris

Inferior rectus

Inferior oblique

Lateral rectus

Inferior divisionof oculomotornerve

Superior division ofoculomotor nerve

Optic nerve

Ciliary ganglion

Figure 23.11. Branches of the oculomotor nerve



Roots: �

1. Motor. Nerve to inferior oblique. Th is is the parasym-pathetic root to supply sphincter pupillae and ciliaris.

2. Sensory. Nasociliary nerve.3. Sympathetic. Internal carotid plexus to supply dilator

pupillae.Branches. � 15–20 short ciliary nerves. Short ciliary nerves supply ciliary body, ciliary muscles of the iris and sphinc-ter pupillae and dilator pupillae muscles. Th e ciliaris and sphincter pupillae are supplied by parasympathetic nerves through oculomotor nerve. Th e dilator pupillae is supplied by the sympathetic nerves.Ciliospinal refl ex. � Irritation of skin of the neck → cervical nerves → reticular formation of the brainstem → lateral horn cells of T1,2 segments of spinal cord → spinal nerve → white rami communicantes → T1,2 sympathetic ganglion → cervical sympathetic chain → superior cervical sympa-thetic ganglion → internal carotid plexus → ophthalmic plexus → ciliary ganglion → dilator pupillae of both sides → dilation of pupils.

TROCHLEAR NERVE (IV CRANIAL NERVE) (Fig. 23.13)

Th is is a motor cranial nerve to supply the superior oblique muscle.Nucleus. It is situated in the lower part of midbrain (Fig. 23.14) within ventral part of periaqueductal grey.

Figure 23.12. Oculomotor nerve

Applied Anatomy

Benedikt’s syndrome. • Ipsilateral paralysis of oculomotor nerve and contralateral hemiplegia, fine tremor on the opposite side.Division of the oculomotor nerve results in the paralysis • of all the muscles of the eyeball except lateral rectus and superior oblique. So the eyeball will be directed laterally.Ptosis or drooping of the upper eyelid results due to injury • of the oculomotor nerve.An aneurysm of the posterior cerebral or superior cerebellar • arteries may compress the oculomotor nerve.During cavernous sinus thrombosis, the • oculomotor nerve may be paralysed.Fractures involving superior orbital fissure may involve • the oculomotor nerve.When the oculomotor nerve is completely destroyed, the • patient shows following features:– Dilatation of pupil– Ptosis– Exophthalmia– Loss of accommodation– Lateral deviation of the eye (lateral squint)– Diplopia—while attempting to move the eye medially.– Glande’s syndrome—ipsilateral oculomotor palsy and

contralateral hemiplegia

CILIARY GANGLION

Situation. � Near the apex of orbit.Size. � Pin head.Structure. � Multipolar neurons.



Trochlearnerve Frontal nerve

Lacrimal nerve

Superior orbital fissure

Optic nerve

Eyeball

Superioroblique

Trochlea

Figure 23.13. Trochlear nerve

Tegmentum

Periaqueductalgrey

Decussation

Inferior colliculus

Nucleus oftrochlearnerve

Trochlearnerve

Figure 23.14. Trochlear nerve nucleus and the course within midbrain

Course. Th e nerve passes forwards within the tegmentum of the midbrain (Fig. 23.15). Th en it runs dorsally. Th e nerves of both sides decussate with each other and pierce the superior medullary velum on the dorsal surface of the midbrain. Th en it winds round the midbrain and reaches the ventral side.

Th en the nerve passes between the posterior cerebral and superior cerebellar arteries. It passes below the free border of the tentorium cerebelli. It crosses the roof of the cavernous sinus and enters the lateral wall of carvernous sinus.

On the lateral wall of the cavernous sinus, it is situated inferior to oculomotor nerve and superior to ophthalmic and maxillary nerves.

It passes through the superior orbital fi ssure lateral to the common tendinous ring and enters the orbit.Termination. It terminates by supplying the superior oblique muscle of the eye.

Figure 23.15. Trochlear nerve emerges from the dorsal surface of midbrain

Connections:Corticonuclear tract �

Medial longitudinal bundle �

Peculiarities of trochlear nerve. It is the only cranial nerve emerging on the dorsal surface of the brain probably due to its morphological supply to the pineal eye.

Right and left nerves completely decussate and go to the opposite side.

Applied Anatomy

• Injury to the trochlear nerve paralyses superior oblique muscle. The patient cannot look downward and medially. Hence while descending a staircase, difficulties are noted. The head is tilted as a compensatory adjustment.

• Injury to the trochlear nerve is rare. It may be involved during cavernous sinus thrombosis.

• Trochlear paralysis causes slight convergent strabismus and diplopia when the eye is moved downwards.

ABDUCENT NERVE(VI CRANIAL NERVE) (Fig. 23.16)

Th is is a motor cranial nerve to supply lateral rectus muscle.Nucleus (Fig. 23.17). Th e nucleus is found in the dorsal part of the pons in the fl oor of the fourth ventricle.

Th e facial nerve winds round this nucleus and forms the facial colliculus.Course within the pons. Th e nerve passes forwards within the tegmentum of the pons.Emergence from the pons (Fig. 23.18). It leaves the pons in between the upper border of pyramid of medulla oblon-gata and lower border of the pons. Here the nerve is situated between the lower border of the pons and anterior inferior cerebellar artery.



It passes forwards and laterally. It pierces the dura mater on the lateral aspect of the dorsum sellae. It bends acutely and laterally. It then passes through the canal of Dorollo under the petroclinoid ligament of Gruber. Th en the nerve enters the cavernous sinus and passes lateral to the internal carotid artery (Fig. 23.19). From here, it passes through the superior orbital fi ssure within the common tendinous ring to enter the orbit.Termination. It terminates by supplying the medial surface of proximal part of the lateral rectus muscle.Connections. Th e nucleus is connected to:

Corticonuclear tract �

Medial longitudinal bundle �

Vestibular nuclei are connected to the abducent nucleus ipsilaterally and contralaterally. Th ese connections help in the vestibular regulation of movements of the eye.

Applied Anatomy

• Arteriosclerosis of the anterior inferior cerebellar artery may compress the abducent nerve at pontomedullary junction. This causes paralysis of lateral rectus muscle.

• Fracture of the base of the skull may involve abducent nerve.

• In cavernous sinus thrombosis, abducent nerve may be compressed and paralysed.

• Gradenigo’s syndrome is due to meningitis near the apex of petrous part of temporal bone. This is characterized by:– Pain in the face– Paralysis of lateral rectus muscle– Severe mastoiditis

• Gradenigo’s syndrome may occur also as a complication of purulent otitis media.

• Millard-Gubler syndrome:– Ipsilateral abducent nerve palsy– Infranuclear type of facial nerve palsy on the same

side– Contralateral hemiplegia

Medial rectus

Superior rectus

Inferior rectus

Lateral rectus

Upper division ofoculomotor nerve

Optic nerveNasociliary nerve

Abducent nerve

Lower divisionof oculomotornerve

Figure 23.16. Abducent nerve supplies lateral rectus muscle

Figure 23.17. Abducent nerve nucleus

Pons

Abducent nerve

Anterior inferiorcerebellar artery

Vertebral arteryMedulla oblongata

Figure 23.18. Abducent nerve as it emerges out of the pons

Course. Th e abducent nerve has the longest intracranial course among the cranial nerves. Th is may be one of the causes for its injury intracranially.

Sphenoidal sinusCavernous sinus

Maxillary nerve

Pituitary gland

Oculomotor nerve

Trochlear nerve

Ophthalmic nerve

Abducentnerve

Internalcarotidartery

Figure 23.19. Abducent nerve within the cavernous sinus



Common disorders affecting oculomotor, trochlear and abducent nerves (Table 23.2)Syphilis, meningitis, encephalitis, botulism, cavernous sinus thrombosis, tumours of the orbit and brain. Aneurysm of internal carotid artery, posterior cerebral artery, drug poison-ing, fractures, etc.

Table 23.2 Syndromes involving oculomotor, trochlear and abdu-cent nerves

Benedikt’s syndrome

Ipsilateral ophthalmoplegia and, contralateral hemiplegia, contralateral hyperkinesia

Gradenigo’s syndrome

Usually it is a complication of purulent otitis media. Pain in the face, lateral rectus muscle paralysis, medial strabismus, diplopia, severe mastoiditis

Graefe’s disease

Chronic progressive ophthalmoplegia. This involves oculomotor , trochlear and abducent nerves in late syphilis or bulbar paralysis

Foville’s syndrome

– Contralateral hemiplegia– Ipsilateral paralysis of facial and abducent nerves

Weber’s syndrome

– Ipsilateral ophthalmoplegia and contralateral hemiplegia

Wernicke’s syndrome

Ethyl alcohol poisoning causes this condition oculomotor or trochlear nerve may be paralysed

Korsakoff’s syndrome

Polyneuritis, loss of memory for recent events, disorientation, confusion

OPHTHALMIC NERVE (V1) (Fig. 23.20)

Th is is a sensory nerve.Commencement. Anterior border of the trigeminal gan-glion.Course. It passes forwards through the lateral wall of the cav-ernous sinus. Here it lies inferior to oculomotor and trochlear nerves. It is situated above the maxillary nerve.

Figure 23.20. Ophthalmic nerve

Figure 23.21. Branches of the trigeminal ganglion

Just before entering the orbit it terminates by dividing into three branches (Fig. 23.21).Termination. It terminates by dividing into: 1. Frontal nerve. 2. Nasociliary nerve. 3. Lacrimal nerve. Th ey enter the orbit through the superior

orbital fi ssure.Th e ophthalmic nerve via its branches supplies:

1. Anterior quadrant of the scalp 2. Cornea 3. Conjunctiva 4. Eyeball 5. Eyelids 6. Nose 7. Frontal and anterior ethmoidal air sinuses 8. Lacrimal gland

Applied Anatomy

Injury to the ophthalmic nerve results in the following clinical features:1. Loss of sensation in the eye2. Loss of sensation in the anterior medial part of the scalp3. Loss of ordinary sensation in the nose4. Loss of sensation in the conjunctiva covering upper eyelid

and front of the eye5. Sneezing cannot be elicited by introducing foreign bodies

into the nose6. Ulceration of the cornea, etc

Frontal Nerve

Commencement. It is the largest branch of the ophthalmic nerve. It is formed within the middle cranial fossa.Course. It enters the orbit through the lateral part of the superior orbital fi ssure and passes above the levator palpebrae superioris muscle.



Termination. Frontal nerve terminates by dividing into: 1. Supratrochlear nerve 2. Supraorbital nerve

Supratrochlear nerveIt is the smaller terminal branch of frontal nerve. It is formed within the orbit. It passes above the trochlea of the superior oblique muscle. Th e nerve is accompanied by the supratro-chlear artery. It curves round the upper border of the orbit and enters the forehead.Th is nerve gives branches to supply: 1. Medial part of eyelids 2. Skin of central portion of the forehead (anterior part of

the scalp)

Supraorbital nerveTh is nerve passes through the supraorbital foramen. Th is nerve is formed within the orbit and leaves the orbit. Th e nerve is accompanied by the supraorbital vessels. It runs in the forehead and the scalp. Th is nerve supplies: 1. Conjunctiva 2. Upper eyelid 3. Skin of the forehead 4. Frontal air sinus 5. Skin of the scalp up to the vertex

So during frontal sinusitis, pain is referred in the forehead and scalp up to vertex.

Nasociliary Nerve (Fig. 23.22)

Commencement. Th is nerve arises from the ophthalmic divi-sion of the trigeminal nerve near superior orbital fi ssure.

Course. Th e nerve passes through the superior orbital fi ssure within the common tendinous ring. It enters the orbit. Th e nerve crosses the optic nerve superiorly from the lateral to medial side.Termination. Th e nerve terminates by dividing into anterior ethmoidal nerve and infratrochlear nerve.

Branches 1. Th e sensory root of ciliary ganglion. 2. Long ciliary nerves—two or three in number. Th ey

supply the eyeball. 3. Posterior ethmoidal nerve. It passes through the posterior

ethmoidal foramen. It supplies the mucous membrane of sphenoidal and ethmoidal air sinuses and nose.

4. Infratrochlear nerve. It supplies medial portion of the eyelids and conjunctiva.

5. Anterior ethmoidal nerve. It is passing through the anterior ethmoidal foramen. It reaches the upper surface of the cribriform plate and divides into medial and lateral nasal branches.

Medial nasal branch: It supplies: 1. Ethmoidal air sinus 2. Frontal air sinus 3. Nasal mucosaLateral nasal branch: It supplies: 1. Skin of the tip of the nose 2. Skin around the anterior nasal opening

Lacrimal Nerve

Th is nerve is formed from the ophthalmic nerve. It passes through the lateral most aspect of the superior orbital fi ssure and enters the orbit. It runs forwards and laterally and supplies: 1. Lateral portion of the eyelids 2. Palpebral conjunctiva 3. Lacrimal gland

Lacrimal nerve communicates with the pterygopalatine ganglion. Th rough this communication, the parasympathetic supply to the lacrimal gland enters the lacrimal nerve.

QUESTIONS

1. Describe the commencement, course, relations, termination, blood supply and structure of the optic nerve. Add a note on its applied anatomy.

2. Describe oculomotor nerve under the following heads:a. Nuclei of originb. Course and relationsc. Termination and muscles suppliedd. Parasympathetic componente. Applied anatomy

3. Describe the detailed anatomy of the trochlear nerve. How this nerve is different from other cranial nerves at its emergence from the brain?

Eyeball

Optic nerve

Ciliary ganglion

Anteriorethmoidalnerve

Long ciliary nerves

Posteriorethmoidalnerve

Communicatingbranch to ciliaryganglion

Nasociliary nerve

Infratrochlearnerve

Figure 23.22. Nasociliary nerve



4. Describe the abducent nerve under the following heads:a. Commencementb. Course and relationsc. Terminationd. Connectionse. Applied anatomyf. Facial colliculus

5. Short notes on:a. Nucleus of the oculomotor nerve

b. Ciliary ganglionc. Muscular branches of oculomotor nerved. Nasociliary nervee. Structure of optic nervef. Optic chiasmag. Supraorbital nerveh. Lacrimal nervei. Optic tractj. Visual pathwayk. Hemianopia


Sample chapter nerves of the orbit-title anatomy for dental students by as moni

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