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Extraocular muscles


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Extraocular muscles

  2. 2. ORBITAL MUSCLES Extrinsic muscles of eyeball. Involved in movement of eyeball. Intrinsic muscles Controls shape of lens and size of pupil.
  3. 3. Extraocular muscles are special The motor units are small, with only from 5 to 18 muscle fibers contact by each motor nerve
  4. 4. Motion of an Eye To describe eye motions we need a set of defined axes (Fick’s Axes - draw on board)  X axis : nasal -> temporal  Y axis: anterior -> posterior  Z axis: superior -> inferior These axes intersect at the center of rotation - a fixed point, defined as 13.5 mm behind cornea.
  6. 6. Ductions (single eye movements)  Rotation about the Z axis (Z axis runs vertically superior to inferior)  Medial Rotation - adduction toward midline  Lateral Rotation - abduction away from midline  Rotation about the X axis (X axis runs horizontally, from nasal to temporal)  Upward, elevation (supraduction)  Downward, depression (infraduction)
  7. 7. Torsion - cyclorotations  Rotation about the Y axis (Y axis runs horizontally, from anterior to posterior)  These are described with respect to a point at 12 o‘clock on the superior limbus  Intorsion (incyclorotation) rotation nasally  Extorsion (excyclorotation) rotation of the 12 o’clock position temporally. Counteracting head tilt (up to 7-9°)
  8. 8. Version & Vergences Some eye movements are paired, that is both eyes do the same thing. . . . Versions Sometimes eyes move in the opposite directions simultaneously. . . Vergences
  9. 9. Vergences Disjunctive eye movements (opposite left- right movments). Non-yolked motion Convergence (simultaneous movement nasally) Divergence (simultaneous temporal movement) Encyclovergence (intorsion) Excyclovergence (extorsion)
  10. 10. Versions (conjugate eyemovement) Dextroversion - rightward gaze (demo) Levoversion - leftward gaze Supraversion - elevation Infraversion - depression  Also up and right, up and left  Down and right, down and leftALL BEHAVIOR IS THAT OF YOLKED EYES
  12. 12. INVOLUNTARY MUSCLES3 muscles. Superior tarsal muscle. Inferior tarsal muscle. Orbitalis.
  13. 13. VOLUNTARY MUSCLES7 in number Levator palpebrae superioris Superior rectus Inferior rectus Medial rectus Lateral rectus Superior oblique Inferior oblique
  14. 14. LEVATOR PALPEBRAESUPERIORIS Superior most muscle in the orbit. Has voluntary and involuntary parts.
  15. 15.  Origin-Inferior surface of lesser wing of sphenoid. Insertion- 1. Upper lamina-Anterior surface of superior tarsus and skin of upper eyelid.2. Middle lamina-superior margin of superior tarsus.3. Lower lamina-Superior conjunctival fornix NERVE SUPPLY- Upper division of occulomotor nerve.
  16. 16. ACTION Elevation of upper eyelid.
  17. 17. PtosisDrooping of upper eyelid. Complete ptosis-injury to occulomotor nerve. Partial ptosis-disruption of postganglionic sympathetic fibres from superior cervical sympathetic ganglion.
  18. 18. SUPERIOR RECTUS MUSCLE  Origin-Superior part of common tendon of zinn.  Insertion-inserted into sclera by flat tendinous insertion(10mm broad)about 7.7 mm behind sclero- corneal junction. Nerve supply-superior division of occulomotor nerve.
  20. 20.  Frontal nerve runs above the superior rectus & levator. The nasociliary nerve and ophthalmic artery run below. The tendon for insertion of the superior oblique muscle runs below the anterior part of the superior rectus.
  21. 21. Action of Superior Rectus Primary action is elevation . . But since the insertion on the globe is lateral as well as superior, contraction will produce rotation about the vertical axis toward midline Thus secondary action is adduction Finally, because the insertion is oblique, contraction produces torsion nasally Intorsion.
  22. 22. INFERIOR RECTUS Origin-inferior part of common tendon of zinn Insertion-in the sclera 6.5 mm behind sclero corneal junction. Nerve supply-inferior division occulomotor nerve.
  23. 23.  Fascial attachments below attached to inferior lid coordinate depression and lid opening. Fascia below Inf. Rectus and Inf. Oblique contribute to the suspensory ligament of lockwood. ACTIONS- Primary depressor. Subsidiary actions are adduction and extorsion.
  24. 24. MEDIAL RECTUS Origin-annulus of zinn and from optic nerve sheath. Insertion-in sclera 5.5mm behind sclero-corneal junction. Nerve supply-lower division of occulomotor nerve. Fascial expansion from muscle sheath forms the medial check ligament and attach to medial wall of orbit.
  25. 25.  Innervation is via cranial nerve III, the oculomotor nerve, and the specific branch runs along the inside of the muscle cone, on the lateral surface. The superior oblique, ophthalmic artery and nasociliary nerve all lie above the medial rectus. ACTION- Primary adductor of the eye.
  26. 26. LATERAL RECTUS Origin-annulus of zinn. Insertion-in the sclera 6.9mm behind sclerocorneal junction. Nerve supply-abducens nerve which enters the muscle on the medial surface.
  27. 27.  The lacrimal artery and nerve run along the superior border. The abducens nerve, ophthalmic artery and ciliary ganglion lie medial to the lateral rectus and between it and the optic nerve. ACTION- Primary abductor of eye.
  28. 28. SPIRAL OF TILLAUX 7.7 mm 5.5 mm6.9mm 6.5 mm
  29. 29. SUPERIOR OBLIQUE Longest and thinnest intraorbital muscle, the muscle ends before the trochlea, tendon is 2.5 cm, smooth movement through trochlea. Origin-body of sphenoid above and medial to optic canal.Passes along superomedial part of orbit and ends in a tendon. Insertion-Posterosuperior quadrant of sclera behind equator of eyeball. Nerve supply-trochlear nerve entering it approximately one third of the distance from the origin to the trochlea.
  30. 30. ACTIONS Primary action-intorsion. Subsidiary actions-abduction and depression. Adducted position-depression.
  31. 31. INFERIOR OBLIQUE Origin-Anteromedial part of orbital floor lateral to nasolacrimal groove. Insertion-posteroinferior surface of globe near the macula. Nerve supply-inferior division of occulomotor nerve enters the muscle laterally at the junction of the inferior oblique and inferior rectus muscles.
  32. 32. ACTIONS Primary action-extorsion. Subsidiary actions-elevations and abduction. Causes elevation only in adducted position of eyeball.
  33. 33. Origins/Insertions of Obliquemuscles
  34. 34. BLOOD SUPPLY Ophthalmic artery. Medial muscular branch-inferior rectus, inferior oblique, medial rectus Lateral muscular branch-superior rectus superior oblique, lateral rectus.