Extraocular Muscles Muscles of the orbit They are

Extraocular Muscles

Muscles of the orbit: They are : 1. Voluntary muscles: B. Two oblique : i. Superior oblique ii. Inferior oblique C. The levator palpebrae superioris elevates the upper eyelid

2. Involuntary muscles: i. Superior tarsal ii. Inferior tarsal & iii. Orbitalis

♠ Extrinsic muscles of eyeball: These consists of four recti and two oblique muscles: ◙ Superior rectus ◙ Superior oblique ◙ Inferior rectus ◙ Inferior oblique ◙ Medial rectus ◙ Lateral rectus

Recti muscles: Origin: All four recti arise in the posterior part of the orbit from the common tendinous ring which bridges across the superior orbital fissure

Insertion: All the recti muscles proceed forward and inserted in front of the equator of the eyeball and behind the sclero-corneal junction

Oblique muscles: Superior oblique: Origin: It arises from the undersurface of the lesser wing above and medial to the common tendinous ring Superior oblique Common tendinous ring

Insertion: The tendon of the muscle passes through a fibrocartilaginous pulley and is inserted into the sclera behind the equator in posterosuperior quadrant of the eyeball Superior oblique Superior rectus Medial rectus Common tendinous ring

Inferior oblique: Origin: It arises from the orbital surface of maxilla in the floor of the orbit Inferior oblique

Insertion: Inserted into the sclera behind the equator in the postero-superior quadrant of the eyeball Lateral rectus Inferior oblique

Nerve supply: All striated ocular muscles are supplied by the Oculomotor nerve except the lateral rectus and superior oblique The Lateral rectus is innervated by the Abducent nerve The Superior oblique is innervated by the Trochlear nerve S O 4; L R 6

Axes of movements: 1. Elevation and depression of eyeball: Takes place around transverse axis passing through the equator 2. Adduction and abduction: Takes place around a vertical axis passing through the equator 3. Torsion of eyeball: (Intorsion & Extorsion) Takes place around antero-posterior axis extending from anterior pole to posterior pole

Axes of movements: Elevation Transverse axis Depression

Axes of movements: Adduction Abduction Vertical axis

Axes of movements: Extorsion Intorsion Antero-posterior axis

Action of individual muscles: LATERAL Inferior oblique A B D Extorsion U C Lateral T rectus I Intorsion O superior N oblique Elevation Depression MEDIAL Superior rectus A D Intorsion D U Medial C rectus T Extorsion I O Inferior N rectus

Eye movements produced by No movement is done by a single muscle, while some muscles: acts as a prime movers and other acts as synergists MOVEMENT Adduction Abduction Elevation Depression Intorsion Extorsion MUSCLE Medial rectus, assisted by superior and inferior recti Lateral rectus, assisted by the superior and inferior oblique muscles Superior rectus and inferior oblique muscles Inferior rectus and superior oblique muscles Superior rectus and inferior oblique Inferior rectus and inferior oblique

Associated movements of eyeball: Normally both eyes move simultaneously and to an equal extent. These associated movements may be conjugate or disjugate 1. Conjugate movements: It occurs when both eyes moves in same direction • Dextro-duction and leavo-duction: Turning both eyes respectively towards right and left sides, around a transverse axis

• Superduction and subduction: both eyes moving respectively above and below, around a transverse axis 2. Disjugate movements: Takes place when the axes of both eyes converge or diverge • Convergence or divergence: when both eyes move around a vertical axis

Factors maintaining the stability of eyeball: Antero-posterior stability: ♣ Balanced action of four recti pulling from behind, and two oblique muscles from front ♣ Check ligaments of medial and lateral recti prevents from posterior displacement ♣ Orbital fat

Vertical stability: ♣ It is maintained by the suspensory ligament of eyeball of Lockwood

Levator palpebrae superioris: It is a triangular sheet of muscle which intervenes between the roof of the orbit and superior rectus muscle Origin: It arises from undersurface of lesser wing of the sphenoid bone Levator palpebrae superioris

Insertion: The muscle ends in an aponeurosis by splitting into three lamellae

Nerve supply: Oculomotor nerve Action: It elevates the upper eyelid

2. Involuntary muscles: These are Superior tarsal, Inferior tarsal and Orbitalis muscle • Superior tarsal: It is derived from the intermediate lamella of levator palpebrae superioris and is attached to superior tarsus It assists in elevation of upper eye lid

• Inferior tarsal: - It connects the inferior tarsus of lower eyelid to the fascial sheet of inferior rectus and inferior oblique - It assists in depression of lower eyelid • Orbitalis: - It streches across the inferior orbital fissure

Applied Anatomy: a. Weakness or paralysis of a muscle causes squint/strabismus. In this condition the two eyes appear to look in different directions b. Nystagmus is characterised by involuntary oscillatory movements of the eyes. This in due to incordination of the ocular muscles

PARASYMPATHETIC GANGLIONS

Parasympathetic ganglion: They are four peripheral parasympathetic ganglion: i. Ciliary ganglion ii. Submandibular ganglion iii. Otic ganglion iv. Pterygopalatine ganglion

i. Ciliary ganglion: ☻ It is topographically connected to Nasociliary nerve but functionally connected with the oculomotor nerve ☻ It contains the cell bodies of multipolar neuron Nasociliary nerve Ciliary ganglion

• Situation: The ganglion is situated near the apex of the orbit, between the optic nerve and the origin of lateral rectus muscle Ciliary ganglion

• Connections: The posterior border of the ganglion is connected with three roots: Motor, Sensory and Sympathetic

a. Parasympathetic/Motor root: The motor root is derived from the nerve to inferior oblique

b. Sensory root: It is derived from the nasociliary nerve. It conveys fibers from the eyeball and pass through Ciliary ganglion. It is concerned with pain, touch and thermal sensations from the eyeball

c. Sympathetic root: It is derived from a branch of internal carotid plexus. It conveys post-ganglionic fibers from the superior cervical sympathetic ganglion

Branches: Anterior border of the ganglion provides about 8 -10 short ciliary branches which contains fibers from all the roots. Short ciliary nerves

ii. Submandibular ganglion: ☻ It is topographically connected to lingual nerve but functionally connected with the facial nerve and chorda tympani ☻ It is relay station for submandibular and sublingual salivary gland ☻ The ganglion presents parasympathetic and sensory roots distributing branches

Parasympathetic root/motor root: The posterior root connecting the ganglion with the lingual nerve forms the parasympathetic root Sympathetic root: It is derived from the plexus around the facial artery Sensory root: It reaches the gland through lingual nerve

iii. Otic ganglion: ☻ It is situated in the infratemporal fossa and topographically connected with the mandibular nerve but functionally connected with the glossopharyngeal nerve

• Situation: The ganglion lies immediately below the foramen ovale.

• Connections: a. Parasympathetic/Motor root: It is derived from lesser petrosal nerve b. Sympathetic root: It is derived from the plexus around the middle meningeal artery and conveys postganglionic fibers from the superior cervical ganglion c. Sensory root: The sensory root comes from the auriculo temporal nerve and is sensory to parotid gland

Branches: a. Post-ganglionic parasympathetic fibers arising from the ganglion join the auriculo-temporal nerve and supply the secreto-motor fibers to the parotid gland b. Post-ganglionic sympathtic fibers, which pass through the ganglion without interruption, join the auriculo-temporal nerve and provide mainly vaso-motor to parotid galnd

c. Fibers from the nerve to medial pterygoid pass through the ganglion without interruption, and supply the tensor veli palitini and tensor tympani muscles d. The otic ganglion is connected to the chorda tympani nerve and the nerve to pterygoid canal, this communicating channel possibly forms an alternate route of taste pathway from the anterior two-third of the tongue to the geniculate ganglion of facial nerve

iv. Pterygo-palatine ganglion: ☻It is the largest peripheral parasympathetic ganglion and occupies the deepest part of the pterygo-palatine fossa ☻Topographically the ganglion is intimately related to the maxillary nerve but functionally it is connected with greater petrosal branch of facial nerve

• Situation: The ganglion is situated lateral to spheno-palatine foramen, below the maxillary nerve and in front of the pterygoid canal

• Connections: a. Parasympathetic/Motor root: It is derived from nerve of pterygoid canal b. Sympathetic root: It is derived from deep petrosal nerve c. Sensory root: It is derived from maxillary nerve and passes through the ganglion without interruption

Branches: The branches of the ganglion are actually branches of the maxillary nerve. They also carry parasympathetic and sympathetic fibers which pass through the ganglion. The branches are: üOrbital branches üPalatine branches: Greater and lesser palatine üNasal branches: Postero-superior lateral nasal and medial nasal branches üPharyngeal branch