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The Sensory System
Chapter 13 - Sensory System - Eye
Question | Answer |
---|---|
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. |