Eye Anatomy, Physiology & Reflexes

40 Question-and-Answer style flashcards covering external and internal anatomy of the eye, clinical conditions, lacrimal apparatus, basic optics, and key concepts of reflex physiology.

What are the three tunics (coats) that form the wall of the eye?

Fibrous tunic, vascular tunic (uvea), and neural tunic (retina).

Which tunic is the outermost protective layer of the eye and what tissue is it made of?

The fibrous tunic; it is composed of avascular connective tissue.

What is the tough, white posterior portion of the fibrous tunic called and what is its primary function?

The sclera; it protects and shapes the eyeball.

Which transparent anterior structure allows light to enter the eye and is part of the fibrous tunic?

The cornea.

Name the five regions of the vascular tunic (uvea).

Choroid, ciliary body, ciliary processes, iris, and pupil.

What is the primary function of the choroid?

It supplies blood to eye tissues and absorbs scattered light via its pigment.

Which part of the vascular tunic contains smooth muscle that controls lens shape?

The ciliary body (specifically, the ciliary muscles).

What do the ciliary processes secrete?

Aqueous humor.

Which pigmented structure gives the eye its color and regulates pupil size?

The iris.

What is the innermost tunic of the eye and what are its two layers?

The neural tunic (retina); it has a pigmented epithelial layer and a neural layer.

Where is the pigmented epithelial layer located and what does it do?

It lines the vascular tunic and helps absorb stray light within the eye.

Which photoreceptors provide the greatest visual acuity and are concentrated in the fovea centralis?

Cones.

What is the optic disc and why is it called the "blind spot"?

The region where the optic nerve exits the eye; it lacks photoreceptors and therefore cannot detect light.

Where is the macula lutea located and what is notable about it?

It lies lateral to the optic disc, directly posterior to the lens; it has a high density of cones and is called the yellow spot.

What is the fovea centralis and why is it important?

The center of the macula lutea containing mostly cones; it is the area of greatest visual acuity.

What structure suspends the lens and helps hold it vertically within the eye?

The suspensory ligament (zonular fibers).

What is the primary function of the crystalline lens?

To focus light onto the retina by changing shape.

Into which two segments does the lens divide the interior of the eye?

Anterior segment (in front of the lens) and posterior segment (behind the lens).

Where is aqueous humor produced, and what does it help maintain?

Produced by the ciliary processes; it helps maintain intra-ocular pressure and nourishes avascular structures.

What is the Canal of Schlemm (scleral venous sinus) responsible for?

Draining aqueous humor from the anterior chamber back into the venous circulation.

Where is vitreous humor located and is it replaced?

In the posterior segment behind the lens; it is a gel-like substance that is never replaced.

What causes glaucoma?

Elevated intra-ocular pressure due to blocked drainage of aqueous humor, which can damage vision.

Define myopia and state how it is corrected.

Nearsightedness; images focus in front of the retina and are corrected with a concave lens.

Define hyperopia and state how it is corrected.

Farsightedness; images focus behind the retina and are corrected with a convex lens.

What optical defect results from irregular curvature of the cornea or lens and causes blurry vision?

Astigmatism.

What term describes a normal eye that can accommodate properly?

Emmetropic eye.

Name the four main components of the lacrimal apparatus in order of tear flow.

Lacrimal gland, lacrimal canals (canaliculi), lacrimal sac, and nasolacrimal duct.

What is the primary function of the lacrimal gland?

It secretes a saline solution (tears) that cleanses and lubricates the eye surface.

What membrane lines the inside of the eyelids and what is its function?

The conjunctiva; it produces mucus to lubricate and protect the eyeball.

What is conjunctivitis?

Inflammation of the conjunctiva (commonly called pink eye).

Where are ciliary (tarsal) glands located and what do they do?

Between eyelash follicles; they secrete an oily substance to lubricate the eye and eyelid.

Define a reflex.

A rapid, predictable, involuntary response to a specific stimulus.

What distinguishes an autonomic reflex from a somatic reflex?

Autonomic reflexes control smooth muscle, cardiac muscle, or glands involuntarily; somatic reflexes stimulate skeletal muscles.

List the five basic components of a reflex arc in order.

Receptor, sensory neuron, integration center, motor neuron, and effector.

What characterizes a monosynaptic reflex, and give an example.

It contains one synapse between two neurons; the patellar (knee-jerk) reflex is an example.

How does a polysynaptic reflex differ from a monosynaptic reflex?

It involves one or more interneurons and therefore at least two synapses within the integration center.

What is the primary purpose of the stretch reflex?

To maintain posture, balance, and muscle tone by causing reflex contraction when a muscle is stretched.

Which cranial nerve mediates the corneal reflex and what is the normal response?

Cranial nerve V (Trigeminal); touching the cornea produces an involuntary blink or wink.

The pupillary light reflex is an example of what type of reflex?

An autonomic reflex involving direct and consensual pupil constriction.

Differentiate general sensory receptors from special sensory receptors.

General receptors detect touch, temperature, pain, and proprioception; special receptors are dedicated to vision, hearing, smell, taste, and balance.