Final Flashcards
what are the accessory structures of the eye
eyebrows
eyelashes
eyelids (palpebrae)
conjunctiva
lacrimal apparatus
eyebrows
located along supraorbital ridge
aid in nonverbal communication and prevent sweat from dripping into eyes
eyelashes
extend from margins of eyelids
prevent objects coming into contact with eye
eyelids
join at medial and lateral palpebral commisures
conjunctive
transpartent lining of eye and lid surfaces
contains numerous goblet cells to moisten eye, many blood vessels to nourish sclera, abundant nerve endings
does not cover cornea so as not to interfere with light passage
ocular conjunctiva
covers anterior sclear (white of eye)
palpebral conjunctiva
covers internal surface of eyelid
lacrimal apparatus
produces, collects, drains lacrimal fluid (tear film)
lacrimal fluid: water, Na+, antibodies, lysozyme (antibacterial)
lubricates, cleanses and moistens eye, reduces eyelid friction, defends against microbes, oxygenates and nourishes cornea
lacrimal gland: produces fluid and secretes it through ducts
-located in superolateral orbit
blinks (15-20 per/min) wash fluid over eye
Lacrimal apparatus flow
- lacrimal gland (orbital and palpebral) push lacrimal fluid through ducts on the eyelid covering the eye and traveling to the lacrimal puncta which then flows fluid into lacrimal canaliculi and down the lacrimal sac into the nasolacrimal duct
fibrous tunic
tough outer layer containing sclera and cornea
vascular tunic
middle layer containing many vessles that includes the iris, ciliary body, and choroid
sclera
white of the eye
composed of dense irregular connective tissue
provides eye shape
protects internal components
attachment site for extrinsic eye muscles
cornea
convex transparent structure at front of eye
limbus: corneal scleral junction
refracts light
choroid
extensive, posterior region of vascular tunic
many capillaries nourish retina
ciliary body
ciliary muscles and processes
located anterior to choroid
ciliary muscles: bands of smooth muscle connected to lens
-muscle contraction loosens suspensory ligaments, altering lens shape
ciliary processes: contain capillaries secreting aqueous humor
iris
gives eye color; most anterior region of uvea
divides the anterior segment into the anterior chamber (between cornea and iris) and posterior chamber (between iris and lens)
pupil is opening in center of iris connecting the two chambers
iris controls pupil diameter
pupillary reflex
alters pupil size in response to light (increased brightness lead to constriction
pupillary constriction
bright light
sphincter pupillae contracts (parasympathetic innervation)
pupil shrinks
pupillary dialation
low light
dialator pupillae contracts (sympathetic innervation)
pupil increases
retina
contains optic disc, mascula lutea, peripheral retina
what are the subtypes of the cells of the neural layer of retina
photoreceptor cells
bipolar cells
ganglion cells
photoreceptor cells
outermost neural layer
contains rods and cones
contain pigments that react to light
bipolar cells
dendrites receive synaptic input from rods and cones
their axons synapse with dendrites of ganglion cells
ganglion cells
their axons gather at optic disc and form optic nerve
optic disc
contains no photoreceptors (blind spot)
where ganglion axons exit toward brain
macula lutea
rounded, yellowish region lateral to optic disc
contains fovea centralis (central pit)
-highest proportion of cones (hardly any rods)
-area of sharpest vision
cones
function in high intensity light and in color vision
peripheral retina
contains primarily rods
functions most effectively in low light
lens
changes shape to focus light on retina
shape determines degree of light refraction
shape is determined by ciliary muscle and suspensory ligaments
when viewing objects 20 ft away or more…
muscle relaxes, suspensory ligaments are tense, lens is flattened
when viewing objects closer than 20 feet
accommodation
muscle tenses, suspensory ligaments are less tense, lens more spherical
vitreous humor (body)
transparent gelatinous fluid in posterior cavity (behind lens)
permanent fluid first produced in embryonic development
helps maintain eye shape
supports retina - keeps it flush against back of eye
aqueous humor
transparent watery fluid in anterior cavity (in front of lens)
continuously produced by ciliary processes
nourishes and oxygenates lens and inner cornea
aqueous humor secretion
- aqueous humor is secreted by the ciliary processes into the posterior chamber
- aqueous humor moves from the posterior chamber through the pupil to the anterior chamber
- excess aqueous humor is reabsorbed into the scleral venous sinus
phototranduction
converting light to electrical signals
performed by photoreceptors
rods
more numerous than cones
primarily located within peripheral retina
specialized for dim light, night vision
cannot distinguish color; poor at sharpness of vision
cones
less numerous than rods
primarily located in fovea centralis
respond to stimulation by bright light
provide color recognition and sharpness of vision
subdivided into blue, green, and red cones
discs within rods and cones contain
photopigment capable of absorbing light
dark adaptation
return of sensitivity to low light levels after bright light
rods must regenerate rhodopsin
may take 20-30 minutes to see well
light adaptation
process of adjusting from low light to bright conditions
pupils constrict but cones initially overstimulated
takes about 5-10 minutes for full adjustment
the ear detects
sound and head movement
signals transmitted via vestibulocochlear nerve (CN VIII)
external ear
auricle
external acoustic meatus
tympanic membrane
auricle
funnel shaped visible part of ear with elastic cartilage
-protects ear entryway and directs sound waves inward
external acoustic (auditory) meatus
ear canal
extends to tympanic membrane
ceruminous glands produce cerumen
-ear wax impedes microorganism growth
tympanic membrane
eardrum
delicate funnel-shaped epithelial sheet
partition between external and middle ear
vibrates when sound waves hit it
transmits sound wave energy into middle ear
middle ear
auditory tube (eustachian tube)
auditory ossicles (stapes, malleus, incus)
eustachian tube / auditory tube
passage extending from middle ear to nasopharynx (upper throat)
equalizes pressure on either side of tympanic membrane