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Orbit and Extra-Ocular Muscles


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Level: Basic; suitable for MBBS, MS Ophthalmology 1st year and Optometry students.

Published in: Health & Medicine

Orbit and Extra-Ocular Muscles

  2. 2. Bony Orbit Seven bones make up the bony orbit:  Frontal  Zygomatic  Maxillary  Ethmoidal  Sphenoid  Lacrimal  Palatine
  3. 3. 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 zygomatic It contains: Infraorbital groove Attachment of Inferior Oblique muscle
  4. 4. 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
  5. 5. 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
  6. 6. Structures passing through Superior orbital fissure
  7. 7. Extraocular Muscles in the orbit
  8. 8. 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)
  9. 9. Voluntary Muscles: 1. Four Recti – Superior, Inferior, Medial and Lateral 2. Two Obliques – Superior & Inferior 3. Elevator of upper eyelid – Levator palpebrae superioris. Involuntary Muscles: 1. Superior tarsal muscle – Deeper part of levator palpebrae superioris 2. Inferior tarsal muscle 3. Orbicularis muscle Extraocular Muscles
  10. 10. Extraocular Muscles
  11. 11. 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
  12. 12. Extraocular Muscles: Origin Common annular tendinous ring
  13. 13. Extraocular Muscles: Origin Superior ObliqueLevator palpebrae superioris Medial Rectus Lateral Rectus Superior Rectus Inferior Rectus Inferior Oblique
  14. 14. Extraocular Muscles Insertion: 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.
  15. 15. Blood Supply: 2 muscular arteries from the ophthalmic artery The 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.
  16. 16. Nerve Supply:  Superior, Inferior & Medial Recti; Levator palpebrae superioris and Inferior Oblique Muscles are supplied by Oculomotor (III cranial) Nerve
  17. 17. Nerve Supply: Trochlear (IV cranial) nerve supplies Superior Oblique [SO4]
  18. 18. Nerve Supply: Abducent (VI cranial) nerve supplies Lateral Rectus [LR6]
  19. 19. 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.
  20. 20. 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)
  21. 21. Actions of Recti Muscles:
  22. 22. Actions of Recti Muscles: Superior rectus: Elevation, Adduction, Intortion Inferior rectus: Depression, Adduction, Extortion Medial rectus: Adduction Lateral rectus: Abduction
  23. 23. 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.
  24. 24. Actions of Oblique Muscles: Superior Oblique: : Intortion Inferior Oblique : Extortion Anteroposterior axis
  25. 25. Actions of Oblique Muscles: Both oblique muscles pull the posterolateral quadrant anteromedially; thus, abduct the eyeball. Vertical axis
  26. 26. Extraocular muscles actions:
  27. 27. 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 RAD LATERAL RECTUS Abducent LR6 Abduction SUPERIOR OBLIQUE Trochlear SO4 Abduction, Depression, Intorsion SIN INFERIOR OBLIQUE Oculomotor Abduction, Elevation, Extorsion
  28. 28. 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.
  29. 29. Superior Oblique Inferior Oblique Superior Rectus Inferior Rectus Medial Rectus Lateral Rectus
  30. 30. • 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