Podcast
Questions and Answers
What is the total number of extraocular muscles (EOMs) in each eye?
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?
Which of the following is NOT a cardinal movement of the extraocular muscles?
What is the specific action of the superior rectus muscle?
What is the specific action of the superior rectus muscle?
Which cranial nerve innervates the superior oblique muscle?
Which cranial nerve innervates the superior oblique muscle?
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What is one of the functions of the extraocular muscles?
What is one of the functions of the extraocular muscles?
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What is a possible cause of extraocular muscle dysfunction?
What is a possible cause of extraocular muscle dysfunction?
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What is a potential consequence of extraocular muscle dysfunction?
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?
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?
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?
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?
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?
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?
Which cranial nerve is responsible for innervating the inferior oblique muscle?
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What is the primary function of the oblique muscles?
What is the primary function of the oblique muscles?
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What is a potential consequence of extraocular muscle dysfunction?
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?
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!
