Chapter 2-Anatomy and Physiology Flashcards
Cornea
The clear membrane at the front of the globe that begins the process of focusing light the eye receives.
Globe/Eyeball
The eye, without its surrounding structure.
Iris
The colored circle of tissues that controls the amount of light entering the eye by enlarging or reducing the size of its aperture, the pupil.
Pupil
The opening in the center of the iris that enlarges or dilates (admitting more light) and reduces or constricts (admitting less light).
Crystalline Lens (Lens)
Part of the optical focusing system of the eye immediately behind the iris.
Vitreous/Vitreous Body
The clear, jelly-like substance that fills the space behind the lens.
Retina
The inner lining of the posterior segment of the eyeball; consists of a layer of light-sensitive cells that convert images from the optical system into electric impulses sent along the optic nerve for transmission to the brain.
Optic Nerve
The nerve that carries electric impulses to the brain’s visual cortex, where they are integrated to produce the sensation of sight.
Axial Length of the Globe
The length of the eyeball from front (cornea) to back (retina), measured through the optical center.
CCT
Central thickness of the cornea.
Pachymetry
An instrument that measures the distance between the corneal epithelium and the corneal endothelium (corneal thickness).
Refractive Power
The ability of a substance to refract light expressed quantitatively by either its index of refraction or it’s refractivity.
Diopters
The unit of measure of the power of a lens.
Adnexa
The tissues and structures surrounding the eye, includes the orbit, extraocular muscles, eyelids, and lacrimal apparatus.
Orbit
The bony cavity in the skull that houses the globe, extraocular muscles, blood vessels, and nerves.
Blowout Fracture
An injury caused by blunt force applied to the eye, creating pressure that fractures the orbital bones.
Extraocular Muscles
The six muscles that attach to the outside of the globe and control it’s movements.
Medial Rectus Muscle
Extraocular muscle attached to the inner (nasal) side of the globe; function is to move the eye inward toward the nose (adduction).
Lateral Rectus Muscle
Extraocular muscle attached to the outer (temperol) side of the globe; moves the eye outward toward the ear (abduction).
Superior Oblique Muscle
Extraocular muscle attached to the upper side of the globe; three functions are to rotate the eye downward and outward and to rotate inward.
Inferior Oblique Muscle
Extraocular muscle attached to the underside of the globe; three functions are to move the eye upward and outward and to rotate the eye outward.
Superior Rectus Muscle
Extraocular muscle attached to the upper side of the globe; three functions are to elevate the eye, turn the eye inward, and rotate the eye inward.
Inferior Rectus Muscle
Extraocular muscle attached to the underside of the globe; three functions are to move the eye downward and inward toward the nose (adduction) and rotate the eye outward.
Binocular Vision
The blending of the separate images seen by each eye into one image; occurs when both eyes are directed toward a single target and perfectly aligned.
Fusion
The blending by the brain of the separate images received by the two eyes so that a single view is perceived even when the eyes move.
Strabismus
A misalignment of the eyes that may cause vision to be disturbed; occurs when the extraocular muscles do not work in a coordinated manner.
Eyelids
The complex movable cover of the purer portion of the eyeball. This consists of an upper and lower component of skin, tarsus, delicate muscles, eyelashes, glands, and conjunctiva.
Palpebral Fissure
The almond-shaped opening between the upper and lower eyelids.
Medial Canthus
The point where the upper and lower eyelids meet on the nasal side.
Lateral Canthus
The point where the upper and lower eyelids on the temporal side.
Anterior
The front part of a structure.
Cilia
The eyelashes.
Trichiasis
An abnormality of the eyelid that causes eyelashes to turn in the wrong direction and rub against the surface of the eye.
Stye/External Hordeolum
An infection or inflammation of a Zeis gland located on the eyelid margin in a lash follicle.
Posterior
Toward the back.
Meibomian Glands
Multiple specialized glands in the upper and lower eyelids that secrete the oily part of the tear film.
Internal Hordeolum
An acute infection of a meibomian gland in the eyelid; when chronic, the condition is called a chalazion.
Chalazion
A chronic inflammation resulting from an obstructed meibomian gland in the eyelid; associated with infection.
Blepharitis
A common inflammation of the eyelid margin.
Tarsus/Tarsal Plate
The dense, plate-like framework within the middle layer of each eyelid that gives the eyelids their firmness and shape.
Orbicularis Oculi
The circular muscle, located in the middle layer of the eyelids, that closes the eye when it contracts, as in winking.
Levator Palpebrae
The muscle attached to the tarsal plate in the middle layer of the upper eyelids that raises the eyelid when it contracts.
Ptosis
Drooping of the upper eyelid most commonly caused by the levator muscle’s inability to lift the eyelid to its full extent. May be congenital or acquired.
Ectropion
A condition in which the eyelid margin is everted (turned) outward from the globe; may be degeneration of or damage to the eyelid tissues.
Entropion
A condition in which the upper or lower lid margin is turned inward.
Conjunctiva
A thin, translucent mucous membrane extending from the outer corneal border over the globe and the inner surface of the eyelids.
Palpebral Conjunctiva
The portion of the conjunctiva that lines the inner eyelids.
Bulbar Conjunctiva
The portion of the conjunctiva that covers the globe to the edge of the cornea.
Fornix/Cul-De-Sac
The loose pocket of conjunctival tissue where the palpebral and bulbar portions of the conjunctiva meet in the recess of the upper and lower lids.
Conjunctivitis
An inflammation of the conjunctiva that causes swelling of the small conjunctival vessels, making the eye appear red; it may be caused by bacterial or viral infection, allergy, or exposure to environmental agents such as chlorinated swimming pool water; also called pink eye.
Subconjunctival Hemorrhage
A rupture of a conjunctival blood vessel that allows blood to flow under the tissue and produces a bright-red flat area on the conjunctiva.
Lacrimal Apparatus
The structures for tear production and drainage.
Tear Film
The moist coating, composed of three layers, that covers the anterior surface of the globe.
Lacrimal Gland
The gland that produces the watery substance making up the middle layer of the tear film; located in the lateral part of the upper lid.
Mucinous
Sticky
Goblet Cell
The type of cell in the conjunctiva that produces the sticky fluid (mucin) that comprises the innermost tear-film layer.
Foreign Body Sensation
A feeling of eye irritation or grittiness.
Schirmer Tear Test
A test that used a strip of filter paper to measure the patient’s tear output and helps to confirm the diagnosis of dry-eye conditions.
Phenol Red Thread Tear Test
A test that aids in the diagnosis of dry eye and uses cotton threads treated with a pH indicator to measure the patient’s tear production.
Upper Punctum
The tiny opening on the upper eyelid margin near the nose, through which tears pass.
Lower Punctum
The tiny opening on the lower eyelid margin near the nose through which tears pass.
Punctum (Plural-Puncta)
The tiny opening on the upper eyelid margin (upper punctum) and lower eyelid margin (lower punctum) near the nose, through which tears pass.
Upper Lacrimal Canaliculus
One of 2 small channels (plural canaliculi) that starts at the punctum in the upper eyelid mad drains tears from the surface of the eye to the lacrimal sac.
Lower Lacrimal Canaliculus
One of 2 small channels (plural canaliculi) that starts at the punctum in the lower eyelid and drains tears from the surface of the eye to the lacrimal sac.
Lacrimal Sac
The sace that holds tears after they pass through canaliculi, which empty through the nasolacrimal duct into the nasal cavity.
Nasolacrimal Duct
The duct through which tears pass from the lacrimal sac into the nasal cavity.
Dacryocystitis
Inflammation of the lacrimal sac; usually caused by blockage or obstruction of the nasolacrimal duct.
Anterior Segment
The front of the eye; includes the structures between the front surface of the cornea and the vitreous.
Posterior Segment
The rear portion of the eye; includes the vitreous and the retina.
Corneal Epithelium
The outermost corneal layer, which lies above Bowman’s membrane and provides defense against infection and injury.
Bowman’s Membrane
The second corneal layer that lies under the outermost epithelium and above the stroma; also known as the anterior limiting membrane.
Corneal Stroma
The third, or middle, corneal layer, which lies under Bowman’s membrane and above Descemet’s membrane; it contributes to corneal rigidity.
Descemet’s Membrane
The fourth corneal layer that lies above the innermost endothelium and below the stroma; it contributes to corneal rigidity.
Corneal Endothelium
The fifth, innermost corneal layer that lies under Descemet’s membrane; it is composed of a single layer of cells that maintains proper fluid balance within the cornea.
Corneal Abrasion
A scratch or other defect in the superficial cornea (epithelium) caused by trauma.
Corneal Ulcer
Pathological condition involving a defect in the corneal surface and associated with inflammation; infectious ulcers are caused by a pathogenic microorganism.
Sclera
The outer fibrous tissue of the globe, which surrounds the cornea and forms the wall of the eye; protects infra ocular contents.
Limbus
The junction between the sclera and the cornea.
Anterior Chamber
The small compartment. Between the cornea and the iris that is filled with a clear, transparent fluid called aqueous humor.
Aqueous Humor
The clear, transparent fluid that fills the anterior chamber.
Anterior Chamber Angle/Filtration Angle
The junction of the cornea and the iris, from which aqueous humor leaves the eye.
Canal of Schlemm
A structure that drains the aqueous humor from the anterior chamber after it has flowed through the trabecular meshwork.
Aqueous Veins
Collector channels.
Uvea/Uveal Tract
The pigmented layers of the eye (iris, ciliary body, and choroid) that contain the majority of the blood vessel supply.
Dilator Muscle
The iris muscle that dilates the pupil in reduced light conditions; fibers from this muscle stretch from the pupil to the outer boundaries of the iris.
Sphincter Muscle
The muscle that encircles the pupil and makes the pupil smaller in response to bright light.
Posterior Chamber
The space between the back of the iris and the front of the vitreous; the crystalline lens is suspended in this chamber, which is filled with aqueous fluid.
Ciliary Body
A band-like structure of muscle and secretory tissue that extends from the edge of the iris and encircles the inside of the sclera.
Ciliary Process
A finger-like extension of the ciliary body that produces aqueous humor.
Ciliary Muscle
The muscle fibers in the ciliary body of the uveal tract that are involved in accommodation.
Choroid
A layer of tissue largely made up of blood vessels that nourishes the retina; it lies between the sclera and the retina in the uveal tract.
Zonule
A transparent fiber that supports the lens by attaching to the ciliary body. Assists in the accommodative process.
Cortex
A clear paste-like protein that surrounds the nucleus of the crystalline lens.
Accommodation
The change in the curvature of the crystalline lens that helps to focus images of objects close to the eye.
Presbyopia
The progressive loss of the accommodative ability of the lens, due to natural processes of aging.
Opacification
Clouding of a structure, as in the normally clear ocular media, most often seen in the cornea or lens; lenticular opacification (cataract) occurs in many people over 65.
Cataract
An opacified or clouded lens.
Floaters
Small particles of dead cells or other debris that become suspended in the vitreous, or particles of the vitreous itself that degenerate in the normal aging process; they cast shadows on the retina and appear as spots or cobwebs.
Pigment Epithelium
The outer layer of the retina; lies against the choroid.
Photoreceptor
A light-sensitive cell.
Rod
The retinal photoreceptor largely responsible for vision in dim light (scotopic or “night vision”) and for peripheral vision.
Cone
The retinal photoreceptor largely responsible for sharp central vision and for color perception.
Optic Disc/Optic Nerve Head
The
Ovation where the central retinal artery enters and the ventral retinal vein, as well as the nerve fibers, exit.
Macula
The specialized area of the retina close to the center of the back of the eye that provides detailed central vision.
Fovea
The center of the macula.
Bipolar Cell
A type of retinal cell that accepts electric (nerve) impulses from the photo-receptors and passes them to the ganglion cells.
Ganglion Cell
The type of retinal cell that accepts electric (nerve) impulses from the bipolar cells and sends the impulses via axons through the optic disc to the brain.
Axon
The long fiber-like portion of a ganglion cell that courses over the surface of the retina and converges at the optic disc.
Physiologic Blind Spot
The sightless “hole” in the normal vision field corresponding to the optic disc where there are no photoreceptors.
Cup
Small central depression on the optic disc.
Cup/Disc Ratio
The fraction that compares the size of the cup to the size to the optic disc.
Rim
The tissue surrounding the cup.
Optic Atrophy
Thinning of the rim;a pale appearance of the cup and rim.
Central Nervous System
The body system consisting of the brain, spinal cord, and peripheral nerves.
(Retrobulbar) Visual Pathway
The route that is taken by light-generated nerve impulses after they leave the eye.
Optic Chiasm
The point behind the eye in the brain where the two optic nerves merge and the axon fibers from the nasal retina of each eye cross to the opposite side.
Optic Tract
The part of the brain between the optic chiasm and the lateral geniculate body.
Lateral Geniculate Body
The part of the brains long the visual pathway where optic fibers synapse to the optic radiations and transmit visual impulses.
Synapse
The connection between nerves, where electric (nerve) impulses are transmitted.
Optic Radiations
The nerve fibers that transmit visual information from the lateral geniculate body.
Visual Cortex
The area of the brain responsible for the initial conscious registration of visual information; the designation of electric (nerve) impulses from the retina.
