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The Sensory System

Chapter 13 - Sensory System - Eye

QuestionAnswer
What is the function of the eyebrows? Protect the eyes. Keep perspiration out of the eyes and shade the eyes from glaring sunlight.
What is the function of the eyelashes? Protect the eyes. Help trap dust.
Palpebrae Eyelids.
Layers of the eyelid. Skin, Skeletal Muscle, Connective Tissue, Conjunctiva
What is ptosis of the lid? The eyelid droops or sags because the patient is unable to lift the eyelid completely. It gives the patient a sleepy appearance.
What is lid lag? The upper eyelid of a person appears to be pulled up too high, thereby exposing the white sclera above the iris. Common in patients with an overactive thyroid.
What do the tarsal glands do? They secrete an oil that coats the surface of the eye and reduces evaporation of tears.
What are the inner and outer canthi? The corners of the eyes.
levator palpebrae superioris Muscle attached to the eyelid. Contraction of this muscle OPENS the eye.
orbicularis oculi Muscle attached to the eyelid. Contraction of this muscle CLOSES the eye.
Conjunctiva A thin mucous membrane that lines the inner surface of the eyelid.
"Pink Eye" Inflammation of the conjunctiva caused by a bacterial infection.
What structure is appears to be "bloodshot"? Conjunctiva
What are the layers of the eyeball? Sclera, Choroid, Retina
Sclera Outermost layer of the eyeball. Made of tough fibrous connective tissue. Cornea is a forward extension of the sclera.
Choroid Middle layer of the eyeball that is attached to innermost layer. Highly vascular (nourishes the retina). Forward extensions: ciliary body, iris.
Retina Innermost layer that lines posterior two-thirds of eyeball. Contains photoreceptors: rodsmost abundant in periphery, cones most abundant in center. Location of optic disk.
Optic Disk Blind spot because there are no rods or cones.
Eyeball Spherical s hape approximately 2 to 3 cm in diameter. Composed of three layers: sclera, choroid, retina.
Rods Located on periphery. Responsible for black and white or night vision.
Cones Located on central part of posterior eye. Concentrated in fovea centralis in center of macula lutea. Responsible for color vision.
Posterior Cavity of Eyeball Between lens and retina. Contains vitreous humor.
Vitreous Humor Gel substance that pushes retina against choroid layer.
Anterior cavity of eyeball. Between lens and cornea. Contains aqueous humor.
Formation and drainage of aqueous humor. Formed by ciliary body. Circulates through pupil behind cornea. Drains through canals of Schlemm.
Muscles of the eye. Extrinsic muscles. Intrinsic muscles.
Extrinsic muscles. Move eyeball in its bony orbit.
Intrinsic muscles Move structures within the eyeball.
Lacrimal gland Structure that secretes tears.
Colored part of the eye. Iris
Lysozyme Enzyme in tears that prevents infection.
Transparent covering over iris. Cornea
"Hole" in the middle of iris that allows light to enter. Pupil
What happens to pupil in increased light conditions? Constricts
What happens to pupil in decreased light conditions? Dilates
Where are photoreceptors in eyeball? Retina
Lens Bends (refracts) light to focus in eye.
Cataract Cloudy lens that blocks light.
Optic Chiasm Site for the crossing of the medial fibers of the optic nerve to the opposite side of brain; located in front of the pituitary gland.
Refraction Bending of light rays to focus on the retina. Lens, primary refracting structure. Focal point on retina.
Errors of refraction. Myopia, Hyperopia, Astigmatism
Myopia Focal point in front of retina.
Hyperopia Focal point behind retina.
Astigmatism Result of irregularly curved cornea.
Created by: ljlindrose61