Eye Anatomy Quiz: Extra Ocular Muscles
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Questions and Answers

What is the primary function of the superior rectus muscle?

  • Abduction
  • Elevation (correct)
  • Extorsion
  • Adduction

Which cranial nerve is responsible for the lateral rectus muscle?

  • 3RD CN
  • 6TH CN (correct)
  • 4TH CN
  • 5TH CN

What is the difference between duction and version?

  • Duction refers to the movement of one eye while version refers to the movement of both eyes (correct)
  • Duction refers to the movement of both eyes while version refers to the movement of one eye
  • Duction refers to vertical movement while version refers to horizontal movement
  • Duction refers to horizontal movement while version refers to vertical movement

What is the function of the inferior oblique muscle?

<p>Extorsion and depression (D)</p> Signup and view all the answers

Which muscle is responsible for adduction?

<p>Medial rectus (C)</p> Signup and view all the answers

What is the type of ocular movement that involves rotation around the anterior-posterior axis?

<p>Torsional movement (B)</p> Signup and view all the answers

Which nerve is associated with strabismus?

<p>Nerve C N III (B)</p> Signup and view all the answers

What is the site of nucleus for the superior division of Nerve C N III?

<p>Midbrain (A)</p> Signup and view all the answers

Which muscle is innervated by the superior division of Nerve C N III?

<p>Levator palpebrae superioris (D)</p> Signup and view all the answers

In which structure is the levator aponeurosis located?

<p>Eyelid (D)</p> Signup and view all the answers

How many divisions does Nerve C N III have?

<p>Two (D)</p> Signup and view all the answers

What is the term for the muscle in the same eye that moves the eye in the same direction as the agonist?

<p>Synergist (A)</p> Signup and view all the answers

What is the term for the condition where the brain turns off the visual processing of one eye due to unequal refractive errors?

<p>Amblyopia (D)</p> Signup and view all the answers

What type of strabismus is characterized by a nerve palsy?

<p>Paralytic squint (B)</p> Signup and view all the answers

What is the term for the pair of muscles, one in each eye, that produce conjugate ocular movements in the same direction of gaze?

<p>Yolk muscles (B)</p> Signup and view all the answers

What is the condition characterized by double vision that persists when one eye is closed and is seen only when both eyes are open?

<p>Binocular diplopia (B)</p> Signup and view all the answers

What is the term for the misalignment of the two eyes?

<p>Strabismus (A)</p> Signup and view all the answers

What is the likely underlying cause of a ⭐ palsy with pupil involvement unless proven otherwise?

<p>Aneurysm (D)</p> Signup and view all the answers

Which of the following structures are innervated by the inferior division?

<p>IR, MR, IO, iris sphincter, and ciliary muscle (A)</p> Signup and view all the answers

What is the primary consequence of damage to the iris sphincter?

<p>Mydriasis (A)</p> Signup and view all the answers

Which of the following is NOT a cause of ⭐ palsy mentioned in the text?

<p>Cerebral vasospasm (D)</p> Signup and view all the answers

What is the likely effect of aneurysm on the inferior division?

<p>Palsy with pupil involvement (A)</p> Signup and view all the answers

Which cranial nerve innervates the contralateral superior oblique muscle?

<p>CN IV (A)</p> Signup and view all the answers

What is a characteristic of the CN IV nerve?

<p>It is a very long and slender nerve (C)</p> Signup and view all the answers

Which muscle is innervated by the contralateral CN IV nerve?

<p>Superior oblique muscle (A)</p> Signup and view all the answers

What is the relationship between the CN IV nerve and the superior oblique muscle?

<p>The CN IV nerve innervates the contralateral superior oblique muscle (A)</p> Signup and view all the answers

Which of the following statements about the CN IV nerve is FALSE?

<p>It is responsible for adduction (D)</p> Signup and view all the answers

Flashcards

Inferior Division of the Eye

The part of the eye containing the inferior rectus, medial rectus, inferior oblique, iris sphincter, and ciliary muscle.

Microvascular Ischemia

Reduced blood flow in small blood vessels, a possible cause of eye muscle palsy.

Aneurysm

A bulge in a blood vessel, potentially causing eye muscle palsy, especially with pupil involvement.

Head Trauma

Injury to the head, possibly causing eye muscle palsy.

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Agonist

The primary muscle that moves an eye in a certain direction.

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Synergist

An eye muscle working in the same direction as the agonist.

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Antagonist

An eye muscle that works in the opposite direction of the agonist.

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Yolk Muscle (Contralateral Synergist)

Pairs of muscles in different eyes that move them together.

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Amblyopia

Lazy eye; decreased vision in one eye due to the brain ignoring that eye's information.

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Anisometropia

Unequal refractive errors between the two eyes.

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Diplopia

Double vision.

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Monocular Diplopia

Double vision seen only with both eyes open.

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Binocular Diplopia

Double vision seen only with both eyes open.

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Strabismus

Misalignment of the eyes.

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Non-Paralytic Strabismus

Eye misalignment with normal muscle movement.

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Paralytic Strabismus

Eye misalignment due to nerve palsy.

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Superior Rectus

Eye muscle that elevates, adducts, and intorts the eye.

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Inferior Rectus

Eye muscle that depresses, adducts, and extorts the eye.

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Lateral Rectus

Eye muscle that abducts the eye.

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Medial Rectus

Eye muscle that adducts the eye.

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Binocular Eye Movements

Combined eye movements for binocular single vision.

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Monocular Eye Movements

Eye movements that don't involve both eyes working together.

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Horizontal Eye Movements

Eye movements in the left-right plane.

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Study Notes

Inferior Division of the Eye

  • Consists of IR (inferior rectus), MR (medial rectus), IO (inferior oblique), iris sphincter, and ciliary muscle
  • Causes of palsy:
  • Microvascular ischemia
  • Aneurysm
  • Head trauma
  • Palsy with pupil involvement is assumed to be secondary to aneurysm until proven otherwise

Muscle Terminology

  • Agonist: primary muscle that moves an eye in a given direction (e.g., right lateral rectus muscle in abduction of the right eye)
  • Synergist: muscle in the same eye that moves the eye in the same direction (e.g., right superior rectus and right inferior oblique muscles)
  • Antagonist: muscle in the same eye that moves the eye in the opposite direction of the agonist (e.g., right medial rectus and lateral medial rectus muscles)
  • Yolk muscles (contralateral synergists): pairs of muscles that produce conjugate ocular movements in the same direction of gaze (e.g., right lateral rectus and left medial rectus)

Amblyopia and Strabismus

  • Amblyopia: lazy eye, vision deficiency in an eye when the brain turns off the visual processing of one eye
  • Anisometropia: unequal refractive errors between the two eyes
  • Diplopia: double vision, classified into:
  • Monocular diplopia: persists when one eye is closed and seen only when both eyes are open
  • Binocular diplopia: seen only when both eyes are open
  • Strabismus (Squint/Crossed Eye): misalignment of the two eyes, classified into:
  • Non-paralytic (Concomitant Squint): movements of both eyes are full, but only one eye is directed towards the fixated target
  • Paralytic Squint: due to nerve palsy
  • Restrictive Myopathy

Anatomy of Extra Ocular Muscles

  • 7 extra ocular muscles, including:
  • Superior rectus: originates from annulus of Zinn, supplied by 3rd CN, functions in elevation, adduction, and intorsion
  • Inferior rectus: originates from annulus of Zinn, supplied by 3rd CN, functions in depression, extortion, and adduction
  • Lateral rectus: originates from annulus of Zinn, supplied by 6th CN, functions in abduction
  • Medial rectus: originates from annulus of Zinn, supplied by 3rd CN, functions in adduction
  • Superior oblique: originates from body of sphenoid bone, supplied by 4th CN, functions in intorsion, depression, and abduction
  • Inferior oblique: originates from orbital surface of maxilla, supplied by 3rd CN, functions in extortion, elevation, and abduction
  • All superior muscles (rectus and oblique) have intorsion, and all inferior muscles (rectus and oblique) have extorsion

Eye Movements

  • Binocular eye movements (Versions): prerequisites of binocular single vision
  • Monocular eye movements (Ductions)
  • Types of ocular movements:
  • Horizontal (adduction and abduction)
  • Vertical (elevation or depression)
  • Torsional (intorsion or extorsion)

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Description

Test your knowledge of the extra ocular muscles in the eye, including their origin, nerve supply, and function. This quiz covers the superior and inferior rectus muscles, including their clinical evaluation. Good luck!

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