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Questions and Answers
What bone is NOT part of the medial wall of the orbit?
What bone is NOT part of the medial wall of the orbit?
Which of the following structures is NOT contained within the orbit?
Which of the following structures is NOT contained within the orbit?
What is the anatomical feature separating the two eyelids?
What is the anatomical feature separating the two eyelids?
Which muscle is responsible for closing the eye?
Which muscle is responsible for closing the eye?
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Which of the following is NOT a part of the orbicularis oculi muscle?
Which of the following is NOT a part of the orbicularis oculi muscle?
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What is the bony opening at the apex of the orbit?
What is the bony opening at the apex of the orbit?
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Which of the following structures is responsible for producing tears?
Which of the following structures is responsible for producing tears?
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Which of the following muscles is NOT an extraocular muscle?
Which of the following muscles is NOT an extraocular muscle?
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Which of the following nerves leaves the anterior surface of the brainstem between the midbrain and the pons?
Which of the following nerves leaves the anterior surface of the brainstem between the midbrain and the pons?
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Which nerve carries afferent fibers from the retina of the eyeball to the visual centers of the brain?
Which nerve carries afferent fibers from the retina of the eyeball to the visual centers of the brain?
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Which of the following nerves enters the dura covering the clivus and continues in a dural canal until it reaches the cavernous sinus?
Which of the following nerves enters the dura covering the clivus and continues in a dural canal until it reaches the cavernous sinus?
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The inferior ophthalmic vein leaves the orbit posteriorly by:
The inferior ophthalmic vein leaves the orbit posteriorly by:
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Which of the following nerves divides into superior and inferior branches just before entering the orbit?
Which of the following nerves divides into superior and inferior branches just before entering the orbit?
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The optic nerve is surrounded by:
The optic nerve is surrounded by:
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Which nerve passes out laterally to supply the lateral rectus muscle?
Which nerve passes out laterally to supply the lateral rectus muscle?
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The trochlear nerve turns medially to enter which muscle?
The trochlear nerve turns medially to enter which muscle?
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Which of the following is NOT a branch of the ophthalmic nerve?
Which of the following is NOT a branch of the ophthalmic nerve?
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What is the function of the ciliary ganglion?
What is the function of the ciliary ganglion?
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What structure lies immediately posterior to the cornea?
What structure lies immediately posterior to the cornea?
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Which of the following structures is responsible for regulating the amount of light entering the eye?
Which of the following structures is responsible for regulating the amount of light entering the eye?
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Which nerve carries the sensory root to the ciliary ganglion?
Which nerve carries the sensory root to the ciliary ganglion?
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Through which structure do the frontal and lacrimal nerves enter the orbit?
Through which structure do the frontal and lacrimal nerves enter the orbit?
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What is the function of the aqueous humor?
What is the function of the aqueous humor?
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Which of the following is NOT a part of the eyeball?
Which of the following is NOT a part of the eyeball?
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What is the shape of the ciliary body?
What is the shape of the ciliary body?
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What is the function of the smooth muscle fibers within the iris?
What is the function of the smooth muscle fibers within the iris?
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What is the name of the point where the optic nerve leaves the retina?
What is the name of the point where the optic nerve leaves the retina?
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What is the structure that forms a complete ring around the eyeball?
What is the structure that forms a complete ring around the eyeball?
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What is the part of the retina that is sensitive to light?
What is the part of the retina that is sensitive to light?
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What is the name of the area with a hint of yellowish coloration in the retina?
What is the name of the area with a hint of yellowish coloration in the retina?
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What is the condition characterized by increased intraocular pressure?
What is the condition characterized by increased intraocular pressure?
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What is the layer of the retina that is firmly attached to the choroid and continues anteriorly over the internal surface of the ciliary body and iris?
What is the layer of the retina that is firmly attached to the choroid and continues anteriorly over the internal surface of the ciliary body and iris?
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Which muscle is responsible for the elevation of the upper eyelid?
Which muscle is responsible for the elevation of the upper eyelid?
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Which nerve innervates the lateral rectus muscle?
Which nerve innervates the lateral rectus muscle?
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What is the action of the inferior rectus muscle?
What is the action of the inferior rectus muscle?
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Which artery is NOT a branch of the ophthalmic artery?
Which artery is NOT a branch of the ophthalmic artery?
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Which muscle is involved in the depression and abduction of the eyeball?
Which muscle is involved in the depression and abduction of the eyeball?
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Which structure drains into the superior ophthalmic vein?
Which structure drains into the superior ophthalmic vein?
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What is the primary function of the medial rectus muscle?
What is the primary function of the medial rectus muscle?
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Which artery supplies blood to the central retinal artery?
Which artery supplies blood to the central retinal artery?
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Study Notes
Learning Objectives
- Understand the anatomical boundaries of the orbit.
- Identify structures located within the orbit.
- Comprehend the anatomy of the eyelids and potential clinical issues.
- Describe the components and functioning of the lacrimal apparatus.
- List extraocular and intraocular muscles associated with eye movement.
- Recognize anatomical details of the eyeball and their clinical implications.
The Orbit
- Bilateral structures located beneath the anterior cranial fossa and anterior to the middle cranial fossa.
- Contains the eyeball, optic nerve, extraocular muscles, lacrimal apparatus, adipose tissue, and associated nerves and vessels.
Bony Orbit
- Shape: Pyramidal
- Roof consists of frontal and sphenoid bones.
- Medial wall includes maxilla, lacrimal, ethmoid, and sphenoid bones.
- Floor formed by maxilla, zygomatic, and palatine bones.
- Lateral wall comprises zygomatic and greater wing of sphenoid bones.
- Apex is located at the optic canal.
Eyelids
- Protective fibromuscular structures with a palpebral fissure separating them.
- Composed of thin skin, subcutaneous tissue, muscle layer, and lined by conjunctiva.
- Orbicularis oculi muscle, supplied by the facial nerve, enables eyelid closure.
- Eyelids assist in moving the eyeball in three dimensions.
Extraocular Muscles & Innervation
- Levator palpebrae superioris: Elevates upper eyelid (Oculomotor nerve).
- Superior rectus: Elevation, adduction, medial rotation (Oculomotor nerve).
- Inferior rectus: Depression, adduction, lateral rotation (Oculomotor nerve).
- Medial rectus: Adduction (Oculomotor nerve).
- Lateral rectus: Abduction (Abducent nerve).
- Superior oblique: Depression, abduction, medial rotation (Trochlear nerve).
- Inferior oblique: Elevation, abduction, lateral rotation (Oculomotor nerve).
Blood Vessels
- Ophthalmic Artery: Main arterial supply for the orbit; a branch of the internal carotid artery.
- Enters through the optic canal alongside the optic nerve with multiple branches including:
- Lacrimal artery
- Central retinal artery
- Posterior ciliary arteries
- Muscular arteries
- Supraorbital artery
- Ethmoidal arteries
- Medial palpebral artery
- Dorsal nasal artery
- Supratrochlear artery.
Venous Drainage
- Superior Ophthalmic Vein: Formed from the union of supraorbital and angular veins; drains into the cavernous sinus.
- Inferior Ophthalmic Vein: Smaller, can drain via superior orbital fissure or inferior orbital fissure.
Innervation
- Optic nerve (not a true cranial nerve) connects retina to brain.
- Oculomotor nerve divides before entering the orbit.
- Trochlear nerve controls superior oblique muscle.
- Abducens nerve innervates lateral rectus muscle.
- The ophthalmic nerve [V1] provides sensory innervation to the orbit; branches into nasociliary, lacrimal, and frontal nerves.
Ciliary Ganglion
- Small parasympathetic ganglion associated with the oculomotor nerve located near the optic nerve.
- Receives parasympathetic fibers from the oculomotor and sympathetic fibers from the superior cervical ganglion.
Eyeball Structure
- Globe-shaped structure located anteriorly in the orbit.
- Consists of various chambers filled with aqueous humor:
- Anterior chamber: between cornea and iris.
- Posterior chamber: between iris and lens.
- Vitreous chamber: behind the lens.
Iris and Retina
- Ciliary Body: Triangular structure providing support for the iris and lens.
- Iris: Colored structure with smooth muscle to control pupil size.
- Retina: Two parts – optic (light-sensitive) and non-visual (covers ciliary body and iris).
- Optic Disc: Origin of the optic nerve; known as the blind spot due to lack of light sensitivity.
- Macula Lutea: Area of high light sensitivity; contains fovea centralis, a depression for acute vision.
Clinical Applications
- Cataract: Opacity of the lens leads to vision impairment.
- Glaucoma: Condition initiated by increased intraocular pressure, potentially damaging the optic nerve.
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Description
This quiz covers the anatomical boundaries of the orbit, structures contained in the orbit, eyelids, lacrimal apparatus, extraocular and intraocular muscles, and the eyeball. It's ideal for medical students and anatomy enthusiasts.
