Quiz 9 - Eye Flashcards
the eye
visual receptors enable us to detect light and to receive detailed visual images
accessory structures to the eye
eyelid, eye lashes, orbital fat, lacrimal glands, conjunctiva
eyelid
protects eyes: “windshield wipers” keeps eyes moist by blinkin
eye lashes
moving hair causes blinking reflex
orbital fat
provides padding and insulation
lacrimal glands
produce lacrimal fluid (tears)
- contains antibodies and lysozyme (kills bacteria)
- protects, moistens and lubricates eye
conjunctiva
epithelium coving inner surface of eyelids and outer surface of the eye
three layers of tunics
fibrous tunic (outer) vascular tunic (middle) neural tunic (inner)
parts of fibrous tunic
sclera and cornea
scelra
“white” of eye - outer protective covering and dense, fibrous connective tissue
cornea
“window” of eye - continuous with the sclera, transparent, most sensitive part of the eye
parts of vascular tunic
choroid iris pupil ciliary body ciliary muscle suspensory ligaments
choroid
middle dark layer that contains blood vessels, delivers oxygen and nutrients to other layers
iris
contains pigment cells and smooth muscle cells, regulates amount of light entering eye
- pupillary sphincter muscles
- pupillary dilator muscles
pupillary sphincter muscles
form concentric circle, contraction decreases pupil
pupillary dilator muscles
extend radially, contraction enlarges pupil
pupil
central opening of iris
pupillary reflexes
close vision and bright light - constrict distant vision and dim light - dilate emotional state - dilate SNS - dilate PNS - constrict
ciliary body
composed mostly of ciliary muscle
ciliary muscle
right of smooth muscle that controls lens shape
suspensory ligaments of lens
hold lens in place
lens
focus the visual image on the retina
for long distance…
ciliary muscles relax
- places tension on ligament
- pulls lens taut
- lens becomes more flat
for closer distance…
ciliary muscles contract
- reducing tension on ligament
- lens becomes more convex
parts of neural tunic
retina
photoreceptors
fovea
optic disc
retina
neural lauyer contains photoreceptors: dark, pigmented layer prevents light scattering
photoreceptors
rods - light sensitive; important in seeing in dim light and peripheral vision (~125 million rods)
cones - important for color vision (~6 million cones) - color blind individuals lacking in # of cones)
fovea
- pine-sized pit containing highest concentration of cones
- site of sharpest vision
- by-passes neural layers to light strikes cones directly
visual acuity and parts
sharpness of vision
- myopia
- hyperopia
- astigmatism
myopia
(nearsightedness) image is focused in front of retina
hyperopia
(farsightedness) image is focused behind retina
astigmatism
condition that causes blurred vision
optic disc
(blind spot) - where axons of retinal neurons gather and exit eye in optic nerve; light focused here will not be seen
chambers of the eye
eyeball is hollow and interior is divided into 2 cavaties
anterior cavity
anterior chamber - filled with aqueous humor posterior chamber (vitreous chamber) - large; contains the gelatinous vitreous humor
aqueous humor
- plasma-like fluid secreted by ciliary body
- supports, nourishes and removes wastes from lens and cornea
posterior cavity (vitreous chamber)
vitreous chamber filled with vitreous humor
vitreous humor
clear, gel-like fluid that:
- transmits light
- supports lens and holds retina against eye wall
- contributes to intraocular pressure
