COT Ocular Anatomy and Physiology 5 — Questions and Answers
Question 1: Which extraocular muscle is the only one innervated by the trochlear nerve (CN IV)?
- Inferior oblique
- Superior oblique (Correct answer)
- Lateral rectus
- Superior rectus
Correct answer: Superior oblique
The trochlear nerve (CN IV) exclusively innervates the superior oblique muscle, which depresses, intorts, and abducts the eye.
Question 2: The crystalline lens receives its nutrition primarily from:
- Retinal blood vessels
- Aqueous and vitreous humor (Correct answer)
- Hyaloid artery remnants
- Ciliary body capillaries
Correct answer: Aqueous and vitreous humor
The avascular crystalline lens depends entirely on diffusion from the aqueous humor anteriorly and vitreous humor posteriorly for nutrients.
Question 3: Which type of collagen is the predominant component of the vitreous humor?
- Type I collagen
- Type II collagen (Correct answer)
- Type IV collagen
- Elastin fibers
Correct answer: Type II collagen
Type II collagen fibrils form the scaffolding of the vitreous gel, interspersed with hyaluronic acid.
Question 4: The pupillary light reflex afferent pathway travels via which cranial nerve?
- Cranial nerve III
- Cranial nerve II (Correct answer)
- Cranial nerve V
- Cranial nerve VII
Correct answer: Cranial nerve II
The afferent limb of the pupillary light reflex travels along cranial nerve II (optic nerve) to the pretectal nucleus in the midbrain.
Question 5: The macula lutea gets its yellow color from which pigments?
- Melanin and rhodopsin
- Lutein and zeaxanthin (Correct answer)
- Xanthophyll and beta-carotene
- Hemoglobin and transferrin
Correct answer: Lutein and zeaxanthin
Lutein and zeaxanthin are carotenoid pigments concentrated in the macula that filter blue light and protect against oxidative damage.
Question 6: Which structure maintains the eye's round shape and prevents it from collapsing?
- Extraocular muscles
- Intraocular pressure (Correct answer)
- Scleral rigidity alone
- Zonular fibers
Correct answer: Intraocular pressure
Intraocular pressure (normal 10–21 mmHg) inflates the globe and maintains its shape for proper optical function.
Question 7: The ora serrata is significant because it marks the:
- Junction of the optic nerve and retina
- Transition between the peripheral retina and pars plana (Correct answer)
- Boundary between the cornea and sclera
- Edge of the optic disc
Correct answer: Transition between the peripheral retina and pars plana
The ora serrata is the serrated anterior border of the neurosensory retina where it transitions to the non-photosensitive pars plana.
COT Ocular Anatomy and Physiology 5
Which extraocular muscle is the only one innervated by the trochlear nerve (CN IV)?