Chapter 14 Flashcards
How does the eye act like a camera?
- Lens of eye adjusts to bring object into focus
- Pupil of eye constricts to allow less light to enter in bright setting or dilates to allow more light to enter in darker setting
- Through bending of light rays, image reaches retina
- Sensitive nerve cell layer of eye
- Image is transmitted to brain for interpretation
What is the sclera?
- White portion of eye
- Tough, fibrous membrane
- Maintains shape of eyeball
- Serves as protective covering for eye
What is the iris?
The colored portion of the eye
What is the pupil?
- an opening in the center of the iris
- controls the amount of light entering the eye
- its diameter is regulated by relaxation and contraction of the iris
What is the conjunctiva?
- a thin mucous membrane layer that lines the anterior part of the eye (is exposed to air and inner part of eyelids)
- it is colorless but appears withe because it covers the sclera
- will look bloodshot if blood vessels become dilated due to irritation
Lacrimal gland?
- located at the upper out edge of each eye
- produces tears
What is the purpose of tears? What do they contain?
- they flow constantly across the conjunctival surfaces to cleanse and lubricate them
- help prevent bacterial infections
- contain lysozyme, an antibacterial enzyme
lacrimal duct
- located at the canthus (inner edge) of the eye
- the spot from which tears drain
eyelids
-continuous with the skin and cover the eyeball, keeping the surface of the eyeball lubricated and protected from dust and debris through blinking
eyelashes
- located along the edges of the eyelids
- further protect the eyeballs by preventing foreign materials and/or insects from getting to the eyeball
what is the uvea?
the vascular middle layer of the eye
-contains the choroid
what is the choroid?
-a layer just beneath the sclera which contains extensive capillaries that provide the blood supply and nutrients to the eye; the iris; and the ciliary body
the lens
-colorless biconvex structure that aids in focusing the images clearly on the sensitive nerve cell layer called the retina
ciliary body
- on each side of the lens
- secretes aqueous humor
- contains muscles responsible for adjusting the lens to view near objects.
suspensory ligaments
- radiate from the ciliary body
- straight fibrils that attach to the lens and hold it in place
- they respond to the contraction and relaxation of the ciliary body muscles to adjust the shape of the lens for proper focusing of the eye
accommodation
- the ability of the lens to focus clearly on objects at various distances
- the thickening and thinning of the lens causes the light rays to bend appropriately so the image will focus clearly on the sensitive nerve cell layer of the eye
- the lens accommodates for the closeness of an object by increasing its curvature to bend the rays more sharply so they will focus on the retina, producing a clear image
retina
- the third innermost layer of the eye
- changes the energy of the light rays into nerve impulses
how are the nerve impulses transmitted?
-via the optic nerve to the brain for interpretation of the image
rods?
cones?
- outer edges of the retina; responsible for vision in dim light and for peripheral vision
- responsible for visualizing colors, central vision, and vision in bright light
fovea centralis
- a small depression within the macula lutea
- where the highest concentration of cones exists
macula lutea
oval, yellowish spot near the center of the retina
central vision
when the image focuses directly on the fovea centralis and the sharpest image is obtained.
optic nerve
-where images from the retina are transmitted to the brain and interpreted as vision
optic disc
- insensitive to light
- no rods or cones
- known as the blind spot
- the center serves as point of entry for the artery that supplies the retina
what are the two cavities of the inner eye?
anterior chamber: in front of the lens and iris and behind the cornea
posterior chamber: between the iris and the suspensory ligaments
-both are filled with aqueous humor that flows freely between them
-the balance of production and absorption of the aqueous humor maintains proper eye pressure
vitreous humor
clear jellylike substance that gives shape to the eyeball
- is not constantly reproduced
- if a puncture occurs and it escapes, it can cause blindness
What is the process of vision
- light ray enters the eye
- light goes through the cornea, aqueous humor, pupil, lens, and vitreous humor to the retina
- once in the retina, sensitive nerve cells transmit the image through the optic nerve to the brain
refraction
the bending of light rays as they pass through the various structures of the eye to produce a clear image on the retina
The four errors of refraction
astigmatism
hyperopia
myopia
presbyopia
biomicroscopy
- ophthalmic examination of the eye by use of a slit lamp and a magnifying lens
- also known as slit-lamp exam
blespharospasm
-a twitching of the eyelid muscle
-due to eye strain or nervous irritability
blephar/o=eyelid -spasm=twitching, involuntary contraction
corneal
-pertaining to the cornea
exotropia
- an obvious outward turning of one eye in relation to the other eye
- also called walleye
floaters
-one or more spots that appear to drift, or “float” across the visual field
ophthalmopathy
-any disease of the eye
ptosis
-blepharoptosis
blindness
-loss of the sense of sight or extreme visual limitations
types of color blindness?
monochromatism: daltonism or achromatic vision
macular degeneration
- progressive deterioration of the retinal cells in the macula due to aging
- known as senile or age-related macular degeneration (ARMD)
- affects central vision
- rarely causes complete blindness b/c only the macula if affected
what are the 2 types of macular degeneration?
- dry form: causes slow, gradual deterioration macula function, blind spots; no known treatment
- wet form: more serious and responsible for the majority of cases of severe visual loss; experience a leakage of fluid from abnormal vessels under the retina; often treated with laser therapy in early stages
night blindness
-nyctalopia
retinal detachment
- partial or complete splitting away of the retina from the pigmented vascular layer called the choroid
- interrupts the vascular supply to the retina and creates a medical emergency b/c ischemia develops
- causes include trauma, changes to the vitreous chamber b/c of aging or inflammation
- symptoms: floating spots, light flashes, losing of vision
- diagnosis: ophthalmoscopic examination
- surgery needed quickly to reposition the detached retina or permanent loss of vision will occur
intraocular lens implant
- surgical process of cataract extraction and insertion of an artificial lens
- restores visual acuity, depth perception, light refraction, and binocular vision
- can be implanted in the anterior chamber or posterior chamber
laser in situ keratomileusis
- LASIK
- procedure that is a form of laser vision correction for myopia (nearsightedness)
pachymetry
- measurement of the thickness of the cornea
- critical in determining the risk for glaucoma
- uses an ultrasonic-wave instrument
slit-lamp exam
- examination of the external and internal structures of the eye
- uses a low-power microscope combined with a high-intensity light source
- also known as biomicroscopy
- examines the eyelids, sclera, conjunctiva, iris, lens, cornea, fluids, and membranes of interior of the eye
What are the functions of the ears
- to hear
- a sensory organ of balance and equilibrium
what is binaural hearing?
-hearing from both sides from an ear on each side of the head
audiologist
a professional that studies hearing, detects and diagnoses hearing loss, rehabilitates individuals with hearing loss
audiology
the field of research devoted to the study of hearing and impaired hearing
What is included in the external ear?
- it is the visual portion of the ear
- auricle or pinna, external auditory canal, and tympanic membrane
what is the auricle or pinna?
the cartilaginous flap that has a fleshy lower portion known as the ear lobe
external auditory canal?
- the tube leading from the auricle to the middle ear
- lined with cilia and modified sweat glands (ceruminous glands)
what do cilia do?
aid in transmitting the sound waves inward
ceruminous glands?
secrete thick, waxy, honey-colored substance that lubricates and protects the ear-called cerumen
what separates the external and middle ear?
the tympanic membrane
what is the tympanic membrane?
a thin, semitransparent membrane that transmits sound vibrations to the inner ear via the auditory ossicles
what are the 3 middle ear bones and what are they collectively called?
- malleus, incus, and stapes
- together known as the auditory ossicles
malleus
- resembles a hammer
- transmits the sound vibration to the second ossicle
incus
- resembles an anvil
- transmits sound to the stapes
stapes
- resembles a tiny stirrup
- transmits sound from incus to the inner ear
eustachian tube
- also called the auditory tube
- connects the middle ear to the pharynx
oval window
separates the middle ear from the inner ear
What are the bony structures of the inner ear?
-the vestibule, cochlea, and semicircular canals
What are the membranous structures of the inner ear?
utricle and saccle (in vestibule that aid in maintaining balance), the cochlear duct (in the cochlear), semicircular canals (inside bony semicircular canals)
vestibule
-central portion of the inner ear
cochlea
- snail-shaped bony structure
- contains endolymph and perilymph that aid in the transmission of sound vibrations
- houses the organ of Corti- the true organ of hearing
- contains tiny hairs that are stimulated by the sound vibrations
semicircular canals
- located behind the vestibule
- help maintain balance
myringotomy
- surgical incision into the eardrum to relieve pressure
- also called a typanotomy
- tubes in the ear to aid in: avoiding a potential spontaneous rupture of the tympanic membrane, relieve pain, restore hearing, improve speech problems and learning deficits, equalize pressure in the middle ear
- tubes are removed after the middle ear heals
conductive deafness
- hearing loss caused by the breakdown of the transmission of sound waves through the middle and/or external ear
- usually from a mechanical defect of: oval or round windows, tympanic membrane, eustachian tube, ear ossicles, external auditory canal, and/or pinna
- defects may occur because of: otosclerosis, otitis media, ruptured tympanic membrane, or impacted cerumen
- diagnosed with an audiometry
impacted cerumen
-excessive earwax
perforation of the tympanic membrane
- rupture of the tympanic membrane
- due to: middle ear trauma-infection, direct injury, barotrauma, explosion, or explosive acoustic trauma
otoscopy
-using a otoscope to view tympanic membrane and outer ear for lesions, cerumen, color, and intactness
tuning fork test
Rinne test
tuning fork test
Weber test
- evaluates auditory acuity and discovers whether a hearing deficit is conductive or sensorineural
- fork on the center of person’s forehead
hearing aids
devices to amplify sound and provide more precise perception and interpretation of communicated words to the individual with a hearing deficit
types of hearing aids?
- in-canal style: completely in ear; hard to manuveur
- in-ear style: in the external ear
- behind the ear style
- body hearing aid
