Podcast
Questions and Answers
What is the total number of extraocular muscles (EOMs) in each eye?
Which of the following is NOT a cardinal movement of the extraocular muscles?
What is the specific action of the superior rectus muscle?
Which cranial nerve innervates the superior oblique muscle?
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What is one of the functions of the extraocular muscles?
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What is a possible cause of extraocular muscle dysfunction?
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What is a potential consequence of extraocular muscle dysfunction?
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Which of the following is an example of an ocular motility disorder?
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Which of the following movements is NOT controlled by the superior rectus muscle?
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What is the common characteristic of the recti muscles?
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What is the primary function of the extraocular muscles in maintaining binocular vision?
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What is a common disorder affecting the extraocular muscles, characterized by misalignment of the eyes?
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Which cranial nerve is responsible for innervating the inferior oblique muscle?
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What is the primary function of the oblique muscles?
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What is a potential consequence of extraocular muscle dysfunction?
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What is the fibrous ring surrounding the optic nerve that the EOMs originate from?
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Study Notes
Anatomy
- There are six extraocular muscles (EOMs) in each eye:
- Lateral rectus
- Medial rectus
- Superior rectus
- Inferior rectus
- Superior oblique
- Inferior oblique
- EOMs are skeletal muscles that surround the eyeball
- They are responsible for moving the eyeball in its socket
Movements
- EOMs work together to produce six cardinal movements:
- Elevation (upward movement)
- Depression (downward movement)
- Adduction (inward movement)
- Abduction (outward movement)
- Intorsion (inward rotation)
- Extorsion (outward rotation)
- Each EOM has a specific action:
- Lateral rectus: abduction
- Medial rectus: adduction
- Superior rectus: elevation and intorsion
- Inferior rectus: depression and extorsion
- Superior oblique: depression and extorsion
- Inferior oblique: elevation and extorsion
Functions
- EOMs are responsible for:
- Moving the eyeball to focus on objects
- Maintaining binocular vision
- Tracking moving objects
- Stabilizing the gaze
- Coordinating with other muscles to maintain posture and balance
Innervation
- EOMs are innervated by three cranial nerves:
- Oculomotor nerve (III): innervates superior rectus, inferior rectus, medial rectus, and inferior oblique
- Trochlear nerve (IV): innervates superior oblique
- Abducens nerve (VI): innervates lateral rectus
- Each cranial nerve has a specific function:
- Oculomotor nerve: controls most EOMs and pupil constriction
- Trochlear nerve: controls superior oblique
- Abducens nerve: controls lateral rectus
Dysfunction
- EOM dysfunction can lead to:
- Strabismus (crossed eyes)
- Diplopia (double vision)
- Ocular motility disorders
- Eye movement disorders
- Vision problems
- Causes of EOM dysfunction include:
- Neurological disorders (e.g. stroke, Parkinson's disease)
- Muscle imbalance or weakness
- Injury or trauma
- Congenital defects
- Aging
Anatomy of Extraocular Muscles (EOMs)
- Six EOMs in each eye: lateral rectus, medial rectus, superior rectus, inferior rectus, superior oblique, and inferior oblique
- EOMs are skeletal muscles surrounding the eyeball, responsible for moving the eyeball in its socket
Movements of EOMs
- Six cardinal movements: elevation, depression, adduction, abduction, intorsion, and extorsion
- Each EOM has a specific action:
- Lateral rectus: abduction
- Medial rectus: adduction
- Superior rectus: elevation and intorsion
- Inferior rectus: depression and extorsion
- Superior oblique: depression and extorsion
- Inferior oblique: elevation and extorsion
Functions of EOMs
- Moving the eyeball to focus on objects
- Maintaining binocular vision
- Tracking moving objects
- Stabilizing the gaze
- Coordinating with other muscles to maintain posture and balance
Innervation of EOMs
- Three cranial nerves innervate EOMs: oculomotor nerve (III), trochlear nerve (IV), and abducens nerve (VI)
- Oculomotor nerve innervates superior rectus, inferior rectus, medial rectus, and inferior oblique
- Trochlear nerve innervates superior oblique
- Abducens nerve innervates lateral rectus
- Each cranial nerve has a specific function:
- Oculomotor nerve: controls most EOMs and pupil constriction
- Trochlear nerve: controls superior oblique
- Abducens nerve: controls lateral rectus
Dysfunction of EOMs
- Can lead to: strabismus, diplopia, ocular motility disorders, eye movement disorders, and vision problems
- Causes of EOM dysfunction include:
- Neurological disorders (e.g., stroke, Parkinson's disease)
- Muscle imbalance or weakness
- Injury or trauma
- Congenital defects
- Aging
Movements
- Eye movements occur in three dimensions: horizontal, vertical, and rotational
- Horizontal movements controlled by lateral rectus (abduction) and medial rectus (adduction)
- Vertical movements controlled by superior rectus (elevation) and inferior rectus (depression)
- Rotational movements controlled by superior oblique (intorsion) and inferior oblique (extorsion)
Anatomy
- Six extraocular muscles (EOMs) originate from the annulus of Zinn, a fibrous ring surrounding the optic nerve
- EOMs classified into two groups: recti muscles (4) and oblique muscles (2)
- Recti muscles are straight and parallel to the orbital axis
- Oblique muscles are at an angle to the orbital axis
Functions
- EOMs work together to move the eye in its socket, rotate the eye to focus on a target, and maintain binocular vision
- EOMs stabilize the gaze during head movements
- EOMs responsible for conjugate gaze (eyes move together) and vergence movements (eyes move inward or outward)
Dysfunction
- Common disorders affecting EOMs: strabismus, esotropia, exotropia, hypertropia, and convergence insufficiency
- Other conditions affecting EOMs: Graves' disease, myasthenia gravis
Innervation
- EOMs innervated by three cranial nerves: oculomotor nerve (CN III), trochlear nerve (CN IV), and abducens nerve (CN VI)
- Cranial nerves innervate specific EOMs: medial rectus, inferior rectus, inferior oblique, superior rectus, superior oblique, and lateral rectus
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Description
Learn about the six extraocular muscles surrounding the eyeball, their functions, and the six cardinal movements they produce. Test your knowledge of eye anatomy and physiology!
