JCAHPO Ocular Anatomy & Physiology 3

Question 1

Which cranial nerve provides sensory innervation to the cornea and is responsible for triggering the blink (corneal) reflex?

Accepted Answer

Cranial nerve V (trigeminal)

Answer

The ophthalmic branch (V1) of the trigeminal nerve (CN V) provides sensory innervation to the cornea; afferent signals from corneal touch trigger the blink reflex.

Question 2

The tear film is composed of three layers. Which layer, produced by goblet cells, is the innermost and provides adhesion to the corneal epithelium?

Accepted Answer

Mucin layer

Answer

The mucin layer, secreted by conjunctival goblet cells, forms the innermost layer of the tear film and converts the hydrophobic corneal surface to hydrophilic for tear adhesion.

Question 3

The choroid is primarily responsible for which function?

Accepted Answer

Supplying oxygen and nutrients to the outer retina

Answer

The highly vascular choroid provides the majority of oxygen and nutrients to the outer retinal layers, including photoreceptors, through diffusion.

Question 4

Accommodation of the lens for near vision involves which action of the ciliary muscle?

Accepted Answer

Ciliary muscle contracts, zonules relax, lens becomes more convex

Answer

When the ciliary muscle contracts, it reduces tension on the zonular fibers, allowing the elastic lens capsule to make the lens more spherical and increase its refractive power for near focus.

Question 5

The cornea derives most of its oxygen supply from which source?

Accepted Answer

Atmospheric oxygen dissolved in tears

Answer

The avascular cornea receives approximately 80% of its oxygen directly from atmospheric oxygen dissolved in the precorneal tear film, with some supplemental supply from aqueous humor and limbal vessels.

(JCAHPO) International Joint Commission Allied Health Personnel in Ophthalmology Practice Test

(JCAHPO) International Joint Commission Allied Health Personnel in Ophthalmology Practice Test

JCAHPO Ocular Anatomy & Physiology 3