Chapter 15: The Special Senses Flashcards
what is the cornea?
transparent area on anterior surface of the eye
what is the pupil?
opening in center of the iris
function of the pupil
transmits light
what is the conjunctiva?
layer of mucous membrane and epithelium that lines the eyelids and anterior eye
what are the tarsal glands?
modified sebaceous glands
what is the function of tarsal glands?
secretions prevent eyelid from sticking
conjunctivitis is also known as
pinkeye
what is conjunctivitis?
inflammation of the conjunctiva
redness of the eye in conjunctivitis is due to __
dialation of blood vessels deep in epithelium of conjunctiva
what things can cause conjunctivitis?
infection, irritation (physical, chemical, allergic) on conjunctival surface
function of lacrimal gland
makes tears
what is the function of tears?
lubricate, nourish, oxygenate and clean the cornea
lacrimal gland contains ___ and ___ that attack invading pathogens
lysozyme; antibodies
what are the three tunics (layers) of the eye?
- outer fibrous
- middle vascular
- inner
what is contained in the outer layer of the eye?
sclera and cornea
what is contained in the middle layer of the eye?
iris, choroid, ciliary body
what is contained in the inner layer of the eye?
retina
what are the 3 functions of the fibrous layer of the eye?
- support and protect
- attachment site for extrinsic eye muscles
- curve of cornea focuses light
light enters first through the __
cornea
the vascular layer of the eye contains ___, ___ and ___
blood vessels; lymphatic vessels; intrinsic muscles of eye
what are the 4 functions of the vascular layer of the eye?
- route for blood vessels/lymphatic to eye
- regulates amount of light (iris)
- secretes / reabsorbs aqueous humour
- controls shape of lens (ciliary body) = focus
what is the iris/
coloured part of the eye
the iris contains __ and __
blood vessels and pigment cells (melanocytes)
the iris is made of 2 layers of
smooth muscle
what is the role of the smooth muscle in the iris?
contraction changes diameter of pupil to control amount of light entering
what is the ciliary body?
thickened region bulging into interior eye
___ connects ciliary body and lens
ring of fibers
what is the choroid?
vascular layer under the sclera
the choroid has an extensive __ network supplying ___ and __ to the neural layer
capillary network; oxygen/nutrients
function of the outer pigmented layer of the retina
absorbs light
the thick inner neural layer of the retina contains ____
photoreceptors
what are the 2 types of photoreceptors?
rods and cones
eye cavities are separated by ____
lens / ciliary body
the anterior cavity of the eye extends from __ to __
cornea to lens
the anterior cavity contains fluid called __
aqueous humor
the anterior cavity contains 2 chambers ___
- anterior chamber
2. posterior chamber
the anterior chamber of the anterior cavity in the eye extends from the ___ to ___
cornea to iris
the posterior chamber in the anterior cavity of the eye extends from ___ to __
iris to ciliary body and lens
the posterior cavity is filled with gelatinous ___
vitreous body
what is the vitreous humor?
fluid part of the vitreous body
what is the ciliary muscle?
smooth muscle ring that projects into the eye
the aqueous humor circulates within the ___ and passes through the __
anterior cavity; pupil
the aqueous humor is secreted by the epithelial cells of the ____
ciliary processes
the aqueous humor diffuses through the ___ to the ___ surface
vitreous body; retinal surface
the aqueous humor leaves the eye at the ___
scleral venous sinus
the aqueous humor flows into veins in the __
sclera
what are the 4 functions of the aqueous humor?
- transports nutrients and wastes
- forms fluid cushion
- helps retain eye shape
- stabilizes position of the retina
the body of the iris is highly __ pigmented ___ tissue
vascular; loose connective
eye colour is determined by genes that influence ___ and ___
density/distribution of melanocytes; density of pigmented epithelium
T/F the cornea is transparent and clear to allow light through
true
the cornea is a dense matrix of multiple layers of __-
collagen fibers
the cornea is ___ and receives oxygen and nutrients from ___
avascular; tears
what is the primary function of the lens?
changes shape to focus image on photoreceptors
what is the sclera?
the white of the eye
what is the sclera made of ?
dense fibrous connective tissue + collagen and elastic fibers
what are 2 functions of the sclera?
- stabilizes eye shape during movement
2. insertion for extrinsic eye muscles
function of the optic nerve
conveys visual information to brain
what are 2 functions of the ciliary body?
- supports lens
2. controls lens shape
____ helps resist the urge of the lens to ball up
tension in ciliary zonule
the retina contains what 4 things?
- photoreceptors
- pigent cells
- supporting cells
- neurons
the two pupillary muscles of the iris are
- dialator pupillae muscles
2. sphincter pupillae muscles
formation of dilator pupillae muscles around pupil
extend radially
the dilator pupillae muscles are innervated by the ___ nervous system
sympathetic
formation of sphincter muscles around pupil
encircle pupil
the sphincter pupillae muscles are innervated by the ___ nervous system
parasympathetic
what is the macula?
patch of retina with lots of photoreceptors
the fovea centralis is the central part of the __
macula
the highest concentration of photoreceptors (sharpest image) is found in the ___
fovea centralis
explain how light is focused in the eye
- light is refracted when it comes in through the cornea and again through aqueous humor into lens and is bent towards focal point
the focal point is a specific point on the __
retina
the focal distance of a lens is the distance between the center of __ and its ___
lens; focal point
the focal distance is determined by two things __ and __
- distance form object to lens
2. shape of lens
T/F the distance from lens to retina can change
false
eyes focus by changing ___ ( a process called __ )
changing shape of the lens; accommodation
for close vision; the ciliary muscle _____ (contracts/relaxes) and moves ____ (towards/away) and ____ (increases/decreases tension in ciliary zonule
contracts; towards; decreases
for distant vision; the cilary muscle ___ and the ciliary zonule ___ on lens
relaxes; pulls
for close vision, the lens is pulled into a ___ shape
spherical
the spherical shape of the lens increases __
refraction
for distant vision, the shape of the lens is __-
flattened
what is the near point of vision?
inner limit of clear vision
the near point of vision is determined by __
lens elasticity
the near point of vision ___ with age
increases
what is the function of the pigmented layer of the retina
prevents visual echoes by absorbing light
what is the site of preliminary processing/integration of visual info?
neural layer of retina
photoreceptors are located closest to the ___ layer
pigmented
rods are highly ___
sensitive
the function of rods
allow vision in dim light
T/F rods can distinguish colour
false
function of cones
colour vision, sharper, clearer images
cones require what kind of light?
intense
rods and cones synapse with ___
bipolar cells
bipolar cells synapse on ___
ganglion cells
what is the innermost layer of the retina?
ganglion cells
axons of ganglionic cells converge at the ___ to form the optic nerve
optic disc
what is the blind spot?
where the optic nerve leaves the eye
blood vessels follow the ___ to supply inner neural layers
optic nerve
cones are most dense at the ___
fovea centralis of the macula
are there rods located in the fovea centralis?
no
cone density directly correlated to ___
visual acuity
maximum density of rods s located at ___
periphery
the visible light spectrum
400-700 nm
rods respond to ___ wavelengths
blue-green
what are the 3 types of cones?
- blue cones
- green cones
- red cones
what is the most abundant type of cones?
red cones
if all three cone types are stimulated, what colour do we see?
white
colour blindness is caused by __
nonfunctional or absent cones
red-green colour blindness is caused by a lack of what type of cones?
red cones
describe the visual pathway
photoreceptors —> bipolar cells —> ganglion cells
the 2 optic nerves reach the diencephalon at the ____
optic chiasm
from the optic chiasm, continue along the ___
optic tracts
about half the fibers from the optic nerve go to the ___ nucleus on the ___ side of the brain and the other half to the ___ side
lateral geniculate; same side, opposite side
what is optic radiation?
bundle of projection fibers linking each lateral geniculate body with visual cortex on the same side
collaterals from fibers synapsing in lateral geniculate bodies go to subconscious processing centers in the ___ and ___
diencephalon and brainstem
what is depth perception?
ability to judge depth / distance by interpreting 3D relationships
depth perception is perceived by comparing ___ within images received by both eyes
relative positions of objects
T/F images form right and left eyes overlap
true
emmetropia is ___ vision
normal
in normal vision; when the ciliary muscle is relaxed and lens flattened, distant image is focused on ___
retinal surface
myopia is ____ vision
nearsightedness
in myopia, the focal distance is too ___
short
in myopia, the image focuses on ___
area in front of retina
shape of the eyeball that causes myopia
too deep (egg-shaped)
in myopia, the resting curvature of the eye is too ___
great
myopia is corrected with ___ lenses
diverging / concave
what is the function of concave lenses?
spreads light rays apart to shift focus onto retina
hyperopia is ___ vision
farsighted
in hyperopia, the focal distance is too __
long
in hyperopia, the image focuses on __
area behind the retina
shape of eyeball with hyperopia
too flat
hyperopia is corrected with ___ lenses
converging / convex
what is the function of convex lenses?
provides additional refraction to focus on retina
