Special senses Pt. 1 Flashcards
general senses of touch (3)
Temperature
Pressure
Pain
Special senses (5)
Smell
Taste
Sight
Hearing
Equilibrium
___ percent of all sensory receptors are
in the ___
70; eyes
Protection for the eye (2)
Most of the eye is enclosed in a bony orbit
A cushion of fat surrounds most of the eye
Accessory Structures of the Eye (9)
eyelids
eyelash
meibomian glands
ciliary glands
conjunctiva
lacrimal apparatus (lacrimal gland and canals)
lacrimal sac
nasolacrimal duct
modified sebaceous
glands produce an oily secretion to lubricate
the eye
meibomian glands
– modified sweat glands
between the eyelashes
Ciliary glands
Membrane that
lines the eyelids; Connects to the surface of the eye; Secretes mucus
to lubricate the eye
conjunctiva
produces lacrimal fluid
Lacrimal gland –
drains lacrimal fluid from eyes
lacrimal canals
provides passage of lacrimal fluid towards nasal cavity
lacrimal sac
empties lacrimal fluid into the nasal cavity
nasolacrimal duct
Function of the Lacrimal Apparatus
Protects, moistens, and lubricates the
eye
Empties into the nasal cavity
Properties of lacrimal fluid
Dilute salt solution (tears)
Contains antibodies and lysozyme
Muscles attach to the outer surface of the eye
Extrinsic (External) Eye Muscles
Produce gross eye movements and make it
possible to follow moving objects
Extrinsic (External) Eye Muscles
the ____is composed of three tunics – coats
while the interior is filled with fluids called ___
eye wall; humors
three tunics:
outside layer - __
middle layer - __
inside layer - ____
outside= fibrous tunic (sclera)
middle= choroid
inside= sensory tunic
fibrous tunic (2)
sclera
cornea
White connective tissue layer
Seen anteriorly as the “white of the eye”
Sclera
Transparent, central anterior portion; Allows for light to pass through; Repairs itself easily
cornea
The only human tissue that can be transplanted
without fear of rejection – no blood vessels
cornea
Blood-rich nutritive tunic; Dark pigment prevents light from scattering
inside the eye
Choroid Layer
the choroid layer is Modified interiorly into two structures
ciliary body
iris
– smooth muscle to which the lends
is attached
Ciliary body
Pigmented layer that gives eye color
Iris
– rounded opening in the iris for light to
enter
Pupil
Contains receptor cells (photoreceptors)
Sensory Tunic (Retina)
photoreceptors in retina
rods
cone
signals pass from photoreceptors via a two-neuron chain
bipolar neurons
ganglion cells
Signals leave the retina toward the brain
through the ___
optic nerve
Most are found towards the edges of the
retina; Allow dim light vision and peripheral vision; Perception is all in gray tone
Rods
Allow for detailed color vision in bright light
Densest in the center of the retina
cones
– area of the retina with only cones– lateral to each blind spot
Fovea centralis
No photoreceptor cells are at the __ or ___ – where the optic
nerve leaves the eyebal
optic
disk, or blind spot
three types of
cones and their wavelengths
blue cones- 420 mm
green cones 530 mm
red cones 560
is the result
of lack of one cone type
Color blindness
Impulses received at the
same time are interpreted
as __
intermediate colors
Biconvex crystal-like structure; Held in place by a suspensory ligament
attached to the ciliary body
lens
Internal Eye Chamber Fluid
Aqueous humor
Vitreous humor
Watery fluid found in chamber between the
lens and cornea; Similar to blood plasma
Aqueous humor
Helps maintain intraocular pressure; provides nutrients for the lens and cornea
aqueous humor
aqueous humor is Reabsorbed into venous blood through the
____
canal of Schlemm
Gel-like substance behind the lens; Keeps the eye from collapsing inward by
reinforcing it internally; Lasts a lifetime and is not replaced
Vitreous humor
form when the
lens becomes increasingly
hard and opaque over time
requiring a transplant or
special glasses
Cataracts
___results when the drainage of
aqueous humor is blocked and pressure
within the eye increases dramatically and
compresses the delicate retina and optic
nerve causing pain and blindness
Glaucoma
Light must be focused
to a point on the ___
for optimal vision –
done by the ___
retina; lens
The resting eye is set
for distance vision
(over ___ ft away)
20
The lens must change
shape to focus for
closer objects –
____
accommodation
Images Formed on the Retina
real; reversed left to right; upside down
Optic nerve crosses
at the ____
to the opposite side
optic chiasma
Visual pathway:
Fiber tracts that
result are the ___
optic tracts
____ contains fibers
from the lateral side of the
eye on the same side and
the medial side of the
opposite eye
Optic tracts
The optic tract fibers
synapse with neurons in
the thalamus, whose axons
form ___
optic radiation
eye reflexes:
____muscles are controlled by the
autonomic nervous system
Internal
Bright light causes pupils to constrict through
action of radial and ciliary muscles –
photopupillary reflex
Viewing close objects causes accommodation
– ___
accommodation pupillary reflex
eye reflex:
__muscles control eye movement to
follow objects
External
Viewing close objects causes ___
(eyes moving medially (toward nose))
convergence
the ear houses two senses
Hearing
Equilibrium (balance)
receptors in ear that respond to physical forces
mechanoreceptors
The ear is divided into
three areas
Outer (external) ear
Middle ear
Inner (internal) ear
__ and __ ear structures involved in
hearing only while ___ear functions in both
equilibrium and hearing
Outer and middle;
inner
Structures of
the external ear
Pinna (auricle)- ear
external auditory canal
Narrow chamber in the temporal bone
Lined with skin
external auditory canal
the external auditory canal have glands that secrete earwax (cerumen)
Ceruminous (wax) glands
the external auditory canal Ends at the ___ where sound waves hit and
cause vibration
tympanic membrane
(eardrum)
