Chapter 14 Flashcards
Eye
One of the body’s special senses that consists of two identical main organs with their associated structures. The function of the eyes is to provide sensory information of visual images that can be interpreted by the visual cortex in the brain to become the sense of sight
Accommodation
Change in the shape of the lens as the muscles of the colliery body contract or relax to move the suspension ligaments to the lens. The lens becomes thicker and more rounded to see objects close by or thinner and flatter to see objects at a distance.
Anterior cavity
Area at the front of the eye that consists of the anterior chamber and the posterior chamber
Anterior chamber
Very small space between the cornea and the iris. Aqueous humor circulates through it
Aqueous humor
Clear, watery fluid produced continuously by the ciliary body. It circulates through the posterior chamber, pupil, and the anterior chamber, as it carries nutrients and oxygen to the cornea and lens.
It drains through the trabecular mesh work, the canal of Schlemm, and is absorbed into the blood in a nearby vein.
Canal of Schlemm
Circular Canal around the iris. Aqueous humor from the trabecular mesh work flows through the canal of Schlemm and is absorbed by a nearby vein.
Choroid
Spongy membrane of blood vessels that begins at the iris and continues around the posterior eye.
In the posterior cavity, it is the middle layer between the sclera and the retina.
Ciliary body
Extension of the choroid. It has suspensions ligaments that hold the lens in place. Muscles in the ciliary body contract or relax to change the shape of the lens.
The ciliary body also produces aqueous humor,
Conjunctiva
Delicate, transparent mucous membrane that covers the inside of the eyelids and the anterior surface of the eye. It produces clear, watery mucus.
Cornea
Transparent layer over the anterior surface of the eye that allows light to enter the eye and bends the light rays.
It is the most sensitive area on the anterior surface of the eye.
It contains no blood vessels but receives oxygen and nutrients from tears on its surface and aqueous humor beneath it.
Cranial nerves III
Oculomotor nerve
Carries motor commands to move four extraocular muscles, move the eyelids, and change the size of the pupil.
Cranial nerve IV
Trochlear nerve
Carries motor commands to move the superior oblique extraocular muscle.
Cranial nerve V
Carries sensory information form the eyelids and eye brows to the brain.
Cranial nerve VI
Carries motor commands to move the lateral Rectus extraocular muscle
Cranial nerve VII
carries motor commands to the lacrimal glands to produce tears.
Extraocular muscles
Six muscles that are attached to the sclera by tendons and move the eye in all directions: Superior Rectus muscle Inferior Rectus muscle Medial Rectus muscle Lateral Rectus muscle Superior oblique muscle Inferior oblique muscle
Eyelashes
Hairs in the eyelids that form a protective barrier that extends outward and keeps foreign substances from coming in contact with the eye.
Eyelids
Pair of fleshy structures above and below the eye. They protect the eye as they blink involuntarily to prevent foreign substances from coming in contact with the eye and to spread tears to keep the eye surface moist.
The eyelids contain the eyelashes and sebaceous glands that secrete oil to keep tears on the surface of the eye.
Iris
Colored, circular structure around the pupil. The color of the iris is determined by genetics.
In dim light, muscles in the iris relax to dilate the pupil.
In bright light, those muscles constrict the pupil.
The iris is a dividing structure between the anterior chamber and the posterior chamber
Lacrimal gland
Gland in the superior-lateral aspect of the eye. It continuously produces and releases tears through the lacrimal duct.
Lacrimal sac
Structure that collects tears as the drain from the medial aspect of the eye. The sac empties into the nano lacrimal duct.
Lens
Transparent, flexible disk posterior to the pupil.
It is surrounded by the lens capsule. Muscles of the ciliary body change the lens shape to become thicker and mor rounded for near vision or thinner and flatter for far vision
Lens capsule
Clear membrane that surrounds the lens
Mitosis
Contraction of the muscles of the iris to constrict (decrease the diameter of) the pupil and limit the amount of bright light entering the eye
Mydriasis
Relaxation of the muscles of the iris to dilate (increase the diameter of) the pupil and increase the amount of light entering the eye
Nasolacrimal duct
Structure that carries tears from the lacrimal sac to the inside of the nose.
Orbit
Hollow bony socket in the anterior skull. It surrounds all but the anterior part of the eye and contains a layer of fat to cushion and protect the eye.
Posterior chamber
Very narrow space posterior to the iris. Aqueous humor circulates through it.
Pupil
Dark, round, central pending in the iris that allows light rays to enter the posterior cavity. In dim light, muscles in the iris relax to dilate the pupil (mydriasis). In bright light, these muscles contract to constrict the pupil (miosis).
Sclera
White, opaque, tough, fibrous, connective tissue that forms the outer layer around most of the eye, protects the internal structures, and maintains the shape of the eye.
Also known as the white of the eye.
The extraocular muscles are attached to the sclera
Trabecular mesh work
Interlacing fivers around the edge of the iris. Aqueous humor drains through it and then goes into the canal of Schlemm.
Uvea
Collective word for the iris, choroid, and ciliary body. Also known as the uveal tract.
Fovea
Small depression in the center of the macula. It is the area of sharpest vision and lies directly opposite the pupil.
Fundus
General word for the retina because it is the area that is farthest from the opening (the pupil)
Macula
Dark, yellow-orange circular area with in distinct edges located on the retina. It contains the fovea.
Optic disk
Bright, yellow-white circle in the retina where the optic nerve and retinal arteries enter, and the retinal veins leave, the posterior cavity. It is not stimulated by light or color images and is known as “the blind spot.”
Optic nerve
Cranial nerve II. It enters the posterior cavity at the optic disk and carries sensory information of visual images from the retina to the optic chias in the brain.
Posterior cavity
Large space between the lens and the retina that is filled with vitreous humor.
Retina
Thin layer of tissue that lines the posterior cavity. Landmarks on the retina include the optic disk and the macula. The retina is also known as the fundus.
Vitreous humor
Clear, gel-like substance that fills the posterior cavity and helps maintain the shape of the eye.
Cones
Light-sensitive cells concentrated in the macula of the retina that detect color. There are three types of cones, each of which responds only to red, green, or blue light.
Optic chiasm
Area of the brain where part of each optic nerve crosses over to join part of the optic nerve from the other side. These combined nerves carry images that merge part of the visual field of one eye with part of the visual field of the other eye.
Optic nerve
Cranial nerve II. It enters the posterior cavity at the optic disk and carries sensory information of visual images from the retina to the optic chiasm in the brain.
Refraction
The bending and focusing of light rays as they pass through the cornea and then through the lens.
Rods
Light-sensitive cells in the retina that detect black and white but not color. Rods function in daytime and nighttime vision.
In low light, they produce a grainy, black-and-white image.
Stereoscopic vision
Three dimensional vision with depth and distance perception
Thalamus
Area in the brain where sensory images can be quickly interpreted so there can be a quick motor reflex to blink or move away.
Visual cortex
Area in the right and left occipital lobes of the brain. It merges the images from both eyes to create a single image, then turns the image right side up and facing in the direction of the original object.
Visual field
The field of vision, including all objects that can be seen, centrally and to the side (peripheral vision)
Blepharitis
Infection or inflammation of the eyelid with redness, crusts, and scales at the bases of the eyelashes. Acute blepharitis is caused by an infection or an allergy.
Chronic blepharitis is caused by rosacea, inflammation of the skin, or microscopic mites that live in the sebaceous glands.
Blepharoptosis
Drooping of the upper eyelid from excessive fat or sagging of the tissues due to age. It can also be from a disease that affects the muscles or nerves.
Ectropion
Injury or a growth on the lower eyelid that causes it to turn outward. Ectropion may also be seen as a birth defect in patients with Down Syndrome or from nerve damage to the facial muscles in patients with Bell palsy.
Entropion
The lower eyelid turns inward becasue of weakening of the muscles and tendons. This causes the lower eyelashes to touch the eye, causing chronic conjunctivitis and pain.
Hordeolum
Red, painful swelling or a pimple containing pus on the eyelid. It is caused by a bacterial infection in a sebaceous gland. Also known as Stye.
Dacryocystitis
Bacterial infection of the lacrimal sac. The sac is painful and contains pus.
Xerophthalmia
Insufficient production of tears resulting in eye irritation. It occurs with aging, because of an ectropion, or as a side effect of certain drugs. Also known as dry eyes syndrome.
Conjunctivitis
Inflamed, reddened, and swollen conjunctiva with dilated blood vessels in the sclera. It may be caused by a foreign substance in the eye, a chemical splashed in the eye, allergens or pollution in the air, chlorinated water in swimming pools, mechanical irritation from eyelashes, or dryness due to a lack of tears.
Corneal abrasion
Damage to the cornea due to trauma or repetitive irritation, such as a foreign particle under a contact lens. A chronic bacterial infection in a corneal abrasion can create a corneal ulcer with sloughing-off of necrotic tissue.
Exophthalmos
Pronounced outward bulging of the anterior surface of the eye with a startled, staring expression. If just one eye is affected, it often has a tumor behind it.
Sclera icterus
Yellow discoloration of the conjunctival, which makes the sclera also appear yellow. It is caused by jaundice due to liver disease.
Nystagmus
Involuntary rhythmic motions of the eye, particularly when looking to the side. Each back and forth motion is known as a “beat”.