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Questions and Answers
What is the structure that forms the roof of the orbital cavity?
What is the structure that forms the roof of the orbital cavity?
Which of the following is NOT a content of the orbital cavity?
Which of the following is NOT a content of the orbital cavity?
Which artery provides blood supply to the medial parts of the eyelids?
Which artery provides blood supply to the medial parts of the eyelids?
Which extraocular muscle is responsible for elevating the upper eyelid?
Which extraocular muscle is responsible for elevating the upper eyelid?
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What is the primary action of the recti muscles of the eye?
What is the primary action of the recti muscles of the eye?
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What is the function of the superior ophthalmic vein?
What is the function of the superior ophthalmic vein?
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Which artery anastomoses with the termination of the facial (angular) artery?
Which artery anastomoses with the termination of the facial (angular) artery?
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Which muscles are classified as intrinsic muscles of the eye?
Which muscles are classified as intrinsic muscles of the eye?
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Which of the following arteries supplies the middle and anterior ethmoidal sinuses?
Which of the following arteries supplies the middle and anterior ethmoidal sinuses?
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Where does the inferior ophthalmic vein end?
Where does the inferior ophthalmic vein end?
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Study Notes
Sense Organs 1: Eye
- The eye is a sense organ.
- By the end of the lecture, students should be able to describe the bony orbit, identify contents of the orbital cavity, and describe extraocular muscles.
Orbital Cavity
- It's a pyramidal space with a base, apex, and four walls.
- Roof: Orbital plate of frontal bone
- Floor: Orbital surface of maxilla, zygomatic bone
- Medial wall: Lacrimal bone, orbital plate of ethmoid bone
- Lateral wall: Zygomatic bone, greater wing of sphenoid bone
Contents of the Orbital Cavity
- Eyeball
- Muscles
- Blood vessels
- Nerves
- Ciliary ganglion
- Lacrimal gland
- Orbital fat
Muscles of the Orbit
-
Extrinsic muscles: Control eye movement
- 4 Recti muscles (superior, inferior, medial, lateral)
- 2 Oblique muscles (superior, inferior)
-
Intrinsic muscles: Control pupil size.
- Dilator pupillae
- Constrictor pupillae
- Ciliary muscle
Extraocular Muscles
- Origin: Common tendinous ring
- Insertion: Sclera anterior to coronal equator of eyeball
- Action: Move the cornea vertically or horizontally (according to muscle name and function)
- Nerve supply: Different muscles are supplied by different nerves (see below)
Superior Oblique Muscle
- Origin: Roof and medial surface of the orbit.
- Insertion: Sclera, posterior to the coronal equator.
- Action: Depression, abduction, and intorsion.
- Nerve supply: Trochlear nerve
Inferior Oblique Muscle
- Origin: Anterior part of the floor of the orbit.
- Insertion: Sclera, posterior to the coronal equator.
- Action: Elevation, abduction, and extorsion.
- Nerve supply: Inferior division of oculomotor nerve
Levator Palpebrae Superioris (LPS)
- Origin: From orbital surface of the roof, anterior superior to optic canal.
- Insertion: Skin of upper eyelid, superior tarsus (Müller's muscle), and superior fornix of conjunctiva.
- Action: Elevates upper eyelid.
Actions of Extraocular Muscles
- Movement around three axes (transverse, vertical, anteroposterior).
- Transverse: Elevation and depression
- Vertical: Abduction and adduction
- Anteroposterior: Intorsion and extorsion.
Nerve Supply of Extraocular Muscles
- All extraocular muscles are supplied by the oculomotor nerve, except the superior oblique and lateral rectus
- Superior oblique: Trochlear nerve
-
Lateral rectus: Abducent nerve
- Other extraocular muscles: Oculomotor nerves (superior and inferior divisions)
Applied Anatomy (Cranial Nerve lesions)
- Cranial nerve 3 lesion: Ptosis, lateral squint, loss of accommodation, dilated pupil, slight proptosis, diplopia.
- Cranial nerve 6 lesion: Medial squint, diplopia.
Intraocular Muscles
- Formed of smooth muscle fibers.
- Have involuntary actions.
- Supplied by autonomic nerves (sympathetic and parasympathetic)
- Include 3 muscles:
- Constrictor pupillae (parasympathetic)
- Dilator pupillae (sympathetic)
- Ciliary muscles (parasympathetic)
Blood Vessels of the Orbit
- Ophthalmic artery: A branch of the internal carotid artery that enters the orbit through the optic canal.
- It supplies the orbit through several branches.
- Supraorbital artery, Dorsal nasal artery, Lacrimal artery and Central retinal artery.
- Fore head, medial and posterior ethmoidal, and branches to orbit.
Ophthalmic Veins
- Superior ophthalmic vein: Receives tributaries, passes through superior orbital fissure, and ends in cavernous sinus. Communicates with supraorbital and angular veins.
- Inferior ophthalmic vein: Begins at the anterior part of the orbit floor, passes through the superior orbital fissure, and ends in the cavernous sinus. Communicates with the pterygoid plexus.
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Description
This quiz focuses on the anatomy of the eye and its associated structures. Students will learn to identify the bony orbit, the contents of the orbital cavity, and the extraocular muscles responsible for eye movement. Prepare to test your understanding of these key aspects of ocular anatomy.
