COST Ocular Anatomy and Physiology Flashcards

The optic nerve exits the eye at which structure, creating a physiologic blind spot?

Answer: Optic disc (optic nerve head)

The optic disc is where retinal ganglion cell axons converge to form the optic nerve; it contains no photoreceptors, producing the normal physiologic blind spot.

Which layer of the choroid is directly adjacent to the outer surface of the retinal pigment epithelium?

Answer: Choriocapillaris

The choriocapillaris is the innermost capillary layer of the choroid and is the primary blood supply for the outer retina, lying just external to Bruch's membrane.

What is the role of the corneal endothelium in maintaining corneal clarity?

Answer: Actively pumping fluid out of the stroma to keep it dehydrated

Corneal endothelial cells use Na+/K+-ATPase pumps to actively remove fluid from the stroma, maintaining its relative dehydration and thus its transparency.

Which muscle of the iris controls the pupillary light reflex by constricting the pupil?

Answer: Sphincter pupillae

The sphincter pupillae, a circular smooth muscle innervated by parasympathetic fibers of CN III, constricts the pupil in response to light (miosis).

The sclera is continuous anteriorly with which transparent tissue?

Answer: Cornea

The sclera transitions into the cornea at the limbus, the corneoscleral junction that is also an important surgical landmark for many ocular procedures.

Which cranial nerve carries parasympathetic fibers that control accommodation and pupillary constriction?

Answer: Cranial nerve III

CN III (oculomotor nerve) carries preganglionic parasympathetic fibers that synapse in the ciliary ganglion, controlling the sphincter pupillae and ciliary muscle.