BIOL 2020 Chapter 17: Special Senses - Vision Flashcards

Vocabulary flashcards covering anatomical structures, muscles, visual pathways, and refraction conditions from BIOL 2020 Chapter 17.

Conjunctiva

A protective mucous membrane that lines the eyelids and covers the sclera.

Tarsal plate

A fold of connective tissue that forms the eyelids and contains sebaceous glands that maintain the tear film.

Stye

An infected gland located within the tarsal plate of the eyelid.

EOM Check

A clinical test of the extraocular eye muscles that evaluates cranial nerves 3 (oculomotor), 4 (trochlear), and 6 (abducens).

Fibrous layer

The outermost layer of the eyeball consisting of the cornea and sclera.

Vascular layer

The middle layer of the eyeball consisting of the choroid, ciliary body, and iris.

Cornea

The transparent component of the fibrous layer that admits and refracts (bends) light.

Sclera

The outer structure of the fibrous layer that provides shape and protects inner parts of the eyeball.

Iris

The structure in the vascular layer that regulates the amount of light entering the eyeball.

Ciliary body

A structure in the vascular layer that secretes aqueous humor and alters the shape of the lens for near or far vision (accommodation).

Choroid

A structure in the vascular layer that provides blood supply and absorbs scattered light.

Sphincter pupillae

Iris muscles under parasympathetic control that contract to constrict the pupil in bright light.

Dilator pupillae

Iris muscles under sympathetic control that contract to dilate the pupil in dim light.

PERRLA

An acronym used during pupil exams standing for Pupils Equal, Round, Reactive to Light and Accommodation.

Anterior segment

The portion of the eye divided into anterior and posterior chambers by the iris, filled with clear, watery aqueous humor.

Posterior segment

The vitreous chamber filled with transparent vitreous humor gel that maintains eye shape and keeps the retina attached to the choroid.

Optic disc

The area where the optic (II) nerve exits the eye, corresponding to the blind spot.

Macula

The region located at the center of the retina.

Fovea centralis

The site in the center of the macula containing the highest visual acuity where vision is sharpest.

Rods

Photoreceptors activated in dim light that contain the photopigment rhodopsin.

Cones

Photoreceptors activated in bright light that produce color vision and contain three different photopigments for red, green, and blue.

Rhodopsin

The photopigment contained inside rods that responds to light.

Vision Pathway

The sequential pathway of light through the eye: Cornea -> Aqueous humor -> Pupil -> Lens -> Vitreous humor -> Photoreceptor cells (retina).

Accommodation

The process where the lens changes shape to focus an object, flattening for distant objects and becoming more spherical (thickening) for close objects.

Presbyopia

The gradual loss of accommodation that occurs after age 40.

Myopia

Nearsightedness where light focuses in front of the retina, corrected using a concave lens.

Hyperopia

Farsightedness where light focuses past the retina, corrected using a convex lens.

Astigmatism

A condition where an irregular curve of the cornea or lens causes blurred or distorted vision.