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Questions and Answers
What is the primary function of the lateral rectus muscle?
What is the primary function of the lateral rectus muscle?
Which artery supplies the retina?
Which artery supplies the retina?
Which muscle is responsible for elevation of the eyeball in the primary position?
Which muscle is responsible for elevation of the eyeball in the primary position?
Which nerve is affected in a squint?
Which nerve is affected in a squint?
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What is the origin of the ophthalmic artery?
What is the origin of the ophthalmic artery?
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Which branch of the ophthalmic artery supplies the lacrimal gland?
Which branch of the ophthalmic artery supplies the lacrimal gland?
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What is the primary function of the Levator Palpebrae Superioris muscle?
What is the primary function of the Levator Palpebrae Superioris muscle?
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What is the origin of the Superior Rectus muscle?
What is the origin of the Superior Rectus muscle?
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What is the term for the drooping of the eyelid?
What is the term for the drooping of the eyelid?
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Which nerve supplies the Levator Palpebrae Superioris muscle?
Which nerve supplies the Levator Palpebrae Superioris muscle?
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What is the insertion point of the Inferior Rectus muscle?
What is the insertion point of the Inferior Rectus muscle?
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What is the average distance from the cornea to the insertion point of the Lateral Rectus muscle?
What is the average distance from the cornea to the insertion point of the Lateral Rectus muscle?
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Which muscle is responsible for constriction of the pupil?
Which muscle is responsible for constriction of the pupil?
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Which nerve supplies the superior oblique muscle?
Which nerve supplies the superior oblique muscle?
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Which of the following muscles is not supplied by the oculomotor nerve?
Which of the following muscles is not supplied by the oculomotor nerve?
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Which of the following is a symptom of paralysis of the levator palpebrae superioris muscle?
Which of the following is a symptom of paralysis of the levator palpebrae superioris muscle?
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Which of the following recti muscles is not supplied by the oculomotor nerve?
Which of the following recti muscles is not supplied by the oculomotor nerve?
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Which structure does the ophthalmic artery pass through?
Which structure does the ophthalmic artery pass through?
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Study Notes
Extra-ocular Muscles
- The primary position of the eyeball is maintained by the action of the extra-ocular muscles
- The superior rectus, inferior rectus, lateral rectus, and medial rectus muscles act on the eyeball
- The superior oblique and inferior oblique muscles also act on the eyeball
Ophthalmic Artery
- Origin: Branch of the internal carotid artery
- Course and relations: Enters the orbit through the optic canal
- Branches:
- Central artery of the retina: most important branch, pierces the optic nerve and runs through it to reach the retina
- Lacrimal artery: to the lacrimal gland
- Muscular branches: to the orbital muscles
- Long and short posterior ciliary arteries: supply the eyeball
- Anterior and posterior ethmoidal arteries: accompany the anterior and posterior ethmoidal nerves
- Supraorbital artery: accompanies the corresponding nerve to the scalp
- Supratrochlear artery: one of the two terminal branches, accompanies the supratrochlear nerve
- Dorsal nasal artery: terminal branch, passes below the trochlea to supply the nose
Levator Palpabrae Superioris
- Origin: From the roof of the orbit in front of the optic canal
- Insertion: Forms three lamellae which are inserted into the skin of the upper eyelid, the superior tarsus, and the superior fornix of the conjunctiva
- Nerve supply: Oculomotor nerve
- Actions: Elevation of the upper eyelid
- Paralysis of levator palpabrae superioris leading to ptosis (dropped eyelid)
Four Recti
- Origin: From the common tendinous ring (ring of Zinn) which surrounds the optic canal
- Insertion: The recti are inserted into the sclera in front of the equator of the eyeball
- Average distances from the cornea:
- Superior rectus: 7.7 mm
- Lateral rectus: 6.9 mm
- Inferior rectus: 6.5 mm
Nerves of the Orbit
- Optic nerve: 1st cranial nerve, passes through the optic canal, nerve of vision
- Oculomotor nerve:
- Origin: Midbrain
- Course: Enters the cavernous sinus, divides into superior and inferior divisions
- Distribution:
- Superior division: supplies superior rectus and levator palpebrae superioris
- Inferior division: supplies medial rectus, inferior rectus, and inferior oblique
- Motor root to the Ciliary ganglion: carries parasympathetic fibers to supply ciliary muscle and sphincter pupillae muscle
- Trochlear nerve:
- Origin: Midbrain at the level of the inferior colliculus
- Course: Enters the cavernous sinus and inter the orbit through the sup orbital fissure
- Distribution: Supplies the superior oblique muscle
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Description
Learn about the extra-ocular muscles that control the movement of the eyelid and eyebone, including the levator palpebrae superioris and others. This quiz covers the anatomy of the orbit and its related muscles.
