orbit and extra-ocular muscles
TRANSCRIPT
DR. SUSHRUT AHALE
ORBIT AND EXTAOCULAR
MUSCLES
Bony Orbit
Seven bones make up the bony orbit: Frontal Zygomatic Maxillary Ethmoidal Sphenoid Lacrimal Palatine
Bony Orbit
ROOF:The orbital roof formed
from both the orbital plate of the frontal bone and the lesser wing of the sphenoid bone. Above the roof is cranial cavity.
Contains: Lacrimal fossa for lacrimal gland
FLOOR:The floor of the orbit is
formed from three bones and related to maxillary sinus:
Maxillary Palatine Orbital plate of the
zygomaticIt contains:Infraorbital grooveAttachment of Inferior
Oblique muscle
Bony Orbit
MEDIAL WALL of the orbit is formed from four bones and related to lateral wall of nose: Frontal process of the
maxillary Lacrimal Orbital plate of the
ethmoidal Lesser wing of the
sphenoid
Lacrimal fossa for lacrimal sac.
LATERAL WALL Formed from two bones: Zygomatic Greater wing of the
sphenoid
Thickest and strongest
Lateral orbital tubercle (Whitnall’s tubercle) for attachment of lateral check ligament
Orbital Foramina The optic foramen: Transmit
Optic nerve and Ophthalmic artery
The supraorbital foramen, or notch: transmit supraorbital nerve and vessels
The zygomatic foramen: Transmit Zygomatic nerve
Infraorbital canal: Transmit Infraorbital nerve and vessels
Superior orbital fissure: Transmit occulomotor nerve, trochlear nerve, abducent nerve, Branches of Ophthalmic nerve, Ophthalmic veins
Inferior orbital fissure: Maxillary nerve
Structures passing through Superior orbital fissure
Extraocular Muscles in the
orbit
Extraocular Muscles
The four recti and two oblique muscles
All are supplied by oculomotor nerve III except superior oblique (Trochlear N) and lateral rectus (Abducent N)
Voluntary Muscles:
1. Four Recti – Superior, Inferior, Medial and Lateral
2. Two Obliques – Superior & Inferior3. Elevator of upper eyelid – Levator palpebrae
superioris.
Involuntary Muscles:
1. Superior tarsal muscle – Deeper part of levator palpebrae superioris
2. Inferior tarsal muscle3. Orbicularis muscle
Extraocular Muscles
Extraocular Muscles
Extraocular Muscles: Origin
4 Recti originate from a common tendinous ring (the annulus of Zinn) which is attached at the apex of the orbit encircling the optic foramina and the medial part of the superior orbital fissure.
SO: arises from the body of sphenoid bone above and medial to the optic foramen
IO: arises by a round tendon from a shallow depression on the orbital plate of maxilla
Extraocular Muscles: Origin
Common annular tendinous ring
Extraocular Muscles: Origin
Superior ObliqueLevator palpebrae superioris
Medial Rectus
Lateral Rectus
Superior Rectus
Inferior RectusInferior Oblique
Extraocular MusclesInsertion: on the sclera
Recti – on sclera in front of equator;distance from cornea – SR = 7.7mm, LR = 6.9mm, IR = 6.5mm, MR = 5.5mm.
Superior Oblique – Behind the equator on sclera in superolateral posterior quadrant, between the superior and lateral recti.
Inferior Oblique – Behind the equator on sclera in inferolateral posterior quadrant, between the recti superior and lateralis.
Blood Supply:
2 muscular arteries from the ophthalmic arteryThe medial (larger) branch supplies the MR, IR
and IO muscles.The lateral (smaller) branch supplies the LR,
SR, SO and levator palpebrae muscles.Anterior ciliary arteries (usually 7) from the
above arteries.Veins correspond to the arteries and empty into
the superior and inferior ophthalmic veins.
Nerve Supply:
Superior, Inferior & Medial Recti; Levator palpebrae superioris and Inferior Oblique Muscles are supplied by Oculomotor (III cranial) Nerve
Nerve Supply:
Trochlear (IV cranial) nerve supplies Superior Oblique [SO4]
Nerve Supply:
Abducent (VI cranial) nerve supplies Lateral Rectus [LR6]
Levator Palpebrae Superioris: Origin: Orbital surface of lesser wing of
sphenoid bone, anterosuperior to optic canal.
Insertion: Splits into two laminas Superior lamina (voluntary) to the skin of
upper eyelid & anterior surface of superior tarsal plate
Inferior lamina (Muller’s muscle) (involuntary) to the upper margin of superior tarsus (superior tarsal or muller’s muscle) & superior conjunctival fornix
Nerve Supply: Oculomotor nerve (voluntary part); Sympathetic (involuntary part, ie Muller’s muscle)
Action: Elevation of upper eyelid. Damage to oculomotor nerve leads to
paralysis of this muscle and leads to ptosis.
Even damage to sympathetic fibers in Horner’s syndrome leads to partial ptosis due to paralysis of Muller’s muscle.
Movements of Eyeball: Along vertical axis : Lateral rotation (Abduction) & Medial
rotation (Adduction) Along Transverse axis: Elevation & Depression Along anteroposterior axis: Intortion (cornea moves
medially from 12 O'clock position) & Extortion (cornea moves laterally from 12 O'clock position)
Actions of Recti Muscles:
Actions of Recti Muscles:Superior rectus: Elevation, Adduction, Intortion
Inferior rectus: Depression, Adduction, Extortion
Medial rectus: Adduction
Lateral rectus: Abduction
Actions of Oblique Muscles:
Superior Oblique: Depression,Abduction,Intortion
Inferior Oblique: Elevation,
Abduction,Extortion
Both the obliques are attached behind the equator and thus, cause opposite movement of the eyeball in the vertical axis.
Actions of Oblique Muscles:
Superior Oblique: : Intortion
Inferior Oblique : Extortion
Anteroposterior axis
Actions of Oblique Muscles:
Both oblique muscles pull the posterolateral quadrant anteromedially; thus, abduct the eyeball.
Vertical axis
Extraocular muscles actions:
Movements of Eyeball:
MUSCLE NERVE SUPPLY
ACTIONS
SUPERIOR RECTUS
Oculomotor Adduction, Elevation, Intorsion SIN
INFERIOR RECTUS
Oculomotor Adduction, Depression, Extorsion
RAD
MEDIAL RECTUS
Oculomotor Adduction RADLATERAL RECTUS Abducent LR6 Abduction
SUPERIOR OBLIQUE Trochlear SO4 Abduction,
Depression, Intorsion
SIN
INFERIOR OBLIQUE
Oculomotor Abduction, Elevation, Extorsion
Applied Anatomy:
Abnormal deviation of the is known as Squint (Strabismus).
Paralysis of Lateral Rectus due to damage to Abducent nerve leads to Medial Squint.
Damage to Oculomotor nerve (3Ds) leads to paralysis of all muscles of eye except Superior Oblique and Lateral Rectus leading to Divergent Squint, Diplopia and Ptosis- Drooping of Eyelid.
Damage to Trochlear nerve cause paralysis of Superior Oblique muscle causing diplopia while looking downwards.
Medial Squint
Divergent Squint and Ptosis -Drooping of Eyelid.
Superior Oblique
Inferior Oblique
Superior Rectus
Inferior Rectus
Medial Rectus
Lateral Rectus
• Causes: Interruption of sympathetic pathway like multiple sclerosis, syringomyelia, traction of stellate ganglion by cervical rib, ganglion metastatic lesion.
• Signs:• Constriction of pupil (miosis) due to paralysis of dilator
pupillae• Slight drooping of eyelid (ptosis) due to paralysis of Muller’s
muscle (Part of Levator palpebrae superioris)• Enophthalmos (Retraction of eyeball) due to paralysis of
Orbicularis muscle which supports the eyeball• Loss of sweating (anhydrosis) due to damage to sympathetic
fibers to the sweat glands• Loss of ciliospinal reflex
Horner’s syndrome