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what are your special senses?
smell, taste, sight, hearing, equilibrium
what are your special sense receptors?
large, complex sensory organs (eye and ear)
localized clusters of receptors (taste buds and olfactory epithelium)
how many receptors are in the eye?
70% of all sensory receptors are in the eye
what are the accessory structures of the eye?
extrinsic eye muscles, eyelids, conjunctiva, lacrimal apparatus
eyelid
opens and closes to protect the eye
meet at medial and lateral commissure (canthus)
eyelashes
glands secrete different lubricants to moisture and protect eye
2 types of glands
tarsal glands
produce an oily secretion that lubricates the eye
ciliary glands
located between the eyelashes
conjunctiva
membrane that lines the eyelid and eyeball
connects with the transparent cornea
secretes mucus to lubricate the eye and keep it moist
Lacrimal apparatus
lacrimal gland and ducts
lacrimal gland
produces lacrimal fluid
situated on lateral end of the eye
lacrimal fluid
tears
path of tears
tears drain across the eye into the lacrimal canaliculi, then the lacrimal sac, and into the nasolacrimal duct, which empties into the nasal cavity
tears contain
dilute salt solution
mucus
antibodies
lysozyme (enzyme that destroys bacteria)
function of tears
cleanses
protect
moisten
lubricate the eye
extrinsic eye muscles
6 muscles attach to the outer surface of the eye
produce gross eye muscles
lateral rectus
moves eye laterally
cranial nerve VI -- abducens
medial rectus
moves eye medially
cranial nerve III -- oculomotor
superior rectus
elevates eye and turns it medially
cranial nerve III -- oculomotor
inferior rectus
depresses eye and turns it medially
cranial nerve III -- oculomotor
inferior oblique
elevates eye and turns it laterally
cranial nerve III -- oculomotor
superior oblique
depresses eye and turns it laterally
cranial nerve IV -- trochlear
internal structures of the eyeball
layers/tunics
humors and fluids
lens
how many layers form the wall of the eyeball?
3
what are they three layers of the eyeball?
fibrous layer
vascular layer
sensory layer
humors and fluids
fill the interior of the eyeball
lens divides the eye. . .
into 2 chambers
fibrous layer of the eyeball
sclera and cornea
sclera
white connective tissue layer
seen anteriorly as the white of the eye
holds structure of the eye
cornea
1st area where light enters the eye
transparent, central anterior portion
allows for light to pass through
repairs itself easily
the only human tissues that can be transplanted without fear or rejection due to lack of blood vessels
vascular layer
blood supply
choroid
ciliary body
iris
pupil
choroid
a blood rich nutritive layer that contains pigment (prevents light from scattering)
how is the choroid modified anteriorly?
into two smooth muscle structures
ciliary body and iris
ciliary body
attached to lens by a suspensory ligament called the ciliary zonule
iris
regulates the amount of light entering the eye
the pigmented layer that gives the eye color
pupil
rounded opening in the iris
while within iris, black part is the back of the retina
sensory layer
photoreceptors
retina and rods and cones
how many layers does the retina contain?
2
what are the two layers of the retina?
outer pigmented layer absorbs light and prevents it from scattering
inner neural layer contains receptor cells (photoreceptors)
what are the photoreceptors?
rods and cones
electrical signals pass from photoreceptors via __________
two neuron chain
what are the two neurons in a two neuron chain?
bipolar cells and ganglion cells
how do signals leave the retina to go to the brain?
via the optic nerve
optic disk
the blind spot
where the optic nerve leave the eyeball
cannot see images focused on the optic disc because it lacks rods and cones
rods
most are found toward the edges of the retina
allow vision in dim light and peripheral vision
all perception is in gray tones
cones
allow for detailed color vision
densest in the center of the retina
fovea centralis
fovea centralis
lateral to the blind spot
area of the retina with only cones
visual acuity is here
visual acuity
sharpest vision
cone sensitivity
3 types of cones (RBG)
each cone type is sensitive to different wavelengths of visible light
what segments does the lens divide the eye into?
anterior segment
posterior segment
anterior segment
aqueous segment
anterior to the lens
contains aqueous humor
posterior segment
vitreous segment
posterior to the lens
contains vitreous humor
aqueous humor
watery fluid found between the lens and cornea
similar to blood plasma
helps maintain intraocular pressure
provides nutrients for the lens and cornea
reabsorbed into venous blood through the sclera venous canal/canal of schlemm
vitreous humor
gel-like substance
prevents eye from collapsing
helps maintain intraocular pressure
ophthalmoscope
instrument used to illuminate the interior of the eyeball and fundus (posterior wall)
can detect diabetes, arteriosclerosis, degeneration of the optic nerve and retina
light must be focused to a point on the ___ for optimal vision
retina
light is _______ by the cornea, aqueous humor, lens, and vitreous humor
bent/refracted
the eye is set for _______
distant vision (over 20 ft away)
accommodation
the lens must change shape to focus on closer objects (less than 20 ft away)
image formed on the retina is a ________
real image
real images are . . .
reversed L from R
upside down
smaller than the object
optic nerve
bundles of axons that exit the back of the eye carrying impulses from the retina
optic chiasma
location where the optic nerves cross
fibers from the medial side of each eye cross over to the opposite side of the brain
optic tracts
contain fibers from the lateral side of the eye on the same side and the medial side of the opposite eye
synapse with neurons in the thalamus
optic radiation
axons from the thalamus run to the occipital lobe
synapse with cortical cells and vision interpretation (seeing) occurs
pathway of impulses from the retina to the point of visual interpretation
optic nerve
optic chiasma
optic tract
thalamus
optic radiation
visual cortex in occipital lobe of the brain
visual fields
overlap for each eye
each eye sees a slightly different view
binocular vision
results and provides depth perception
depth perception
three-dimensional vision
emmetropia
eye focuses images correctly on the retina (normal vision)
myopia
nearsightedness
distant objects appear blurry
light from those objects fails to reach the retina and are focused in front of it
results from having an eyeball that is too long
hyperopia
farsightedness
near objects appear blurry, whereas distant objects are clear
distant objects are focused behind the retina
results from an eyeball that is too short or from a lazy lens
astigmatism
images are blurry
results from light focusing as lines, not points, on the retina because of unequal curvatures of the cornea or lens
convergence
reflexive movement of the eyes medially when we focus on a close object (going cross eyed when a pen is brought to your nose)
photopupillary reflex
bright light causes pupils to constrict
accommodation pupillary reflex
viewing objects causes PUPILS to constrict
how many senses does the ear house?
2 senses
what are the two senses that the ear houses?
hearing and equilibrium (balance)
what are the receptors in the ear?
mechanoreceptors
how many areas is the ear divided into?
3
what are the divisions of the ear?
external (outer) ear
middle ear
internal (inner) ear
external (outer) ear
auricle (pinna)
external acoustic meatus (auditory canal)
only involved in collecting sound waves
external acoustic meatus (auditory canal)
narrow chamber in the temporal bone
lined with skin and ceruminous (earwax) glands
glands secrete cerumen (earwax)
cerumen traps foreign objects and repels insects
ends at the tympanic membrane (eardrum)
middle ear cavity (tympanic cavity)
air-filled mucosa-lined cavity within the temporal bone
involved in sense of hearing
located btwn tympanic membrane and by a bony wall with two openings
pharyngotympanic tube
3 bones (ossicles)
what are the two openings in the middle ear?
oval window and round window
pharyngotympanic tube
aka auditory tube
links the middle ear cavity with the throat
equalizes pressure in the middle ear cavity so the eardrum can vibrate
what are the three bones in the middle ear?
the auditory ossicles are the malleus (hammer), incus (anvil), and stapes (stirrup)
function of the auditory ossicles
transmit and amplify vibrations from the tympanic membrane to fluids of the inner ear
vibrations travel from the hammer→anvil→stirrup→oval window of the inner ear
internal (inner) ear
includes sense organs for hearing and balance
bony labyrinth/osseous labyrinth
filled with perilymph (bony labyrinth)
filled with endolymph (membranous labyrinth)
what does the osseous labyrinth consist of?
cochlea
vestibule
semicircular canals
spiral of corti
located within the cochlear duct
receptors= hair cells on basilar membrane
gel-like tectorial membrane is capable of bending hair cells
cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe
pathways of vibrations from the sound waves
auricle (pinna)
external acoustic meatus (auditory canal)
Tympanic membrane
ossicles amplify the sound waves
oval window
basilar membrane in the spiral organ of corti
hair cells of the tectorial membrane are bent when the basilar membrane vibrates against it
an AP starts in the cochlear nerve (cranial nerve VIII)
impulse travels to the auditory cortex in the temporal lobe
high pitched sounds
disturb the short, stiff hairs/fibers of the basilar membrane
receptor cells close to the oval window are stimulated
low pitched sounds
disturb the long, floppy hairs/fibers of the basilar membrane
specific hair cells further along the cochlea are affected
equilibrium
2 types
static
dynamic
equilibrium receptors
vestibular apparatus
static equilibrium
balance concerned with changes in the position of the head
maculae
receptors in the vestibule
report on position of the head
help us keep our head erect
send info via vestibular nerve to the cerebellum of the brain
anatomy of the maculate
hair cells are embedded in the otolithic membrane, otoliths float in a gel around hair cells, movements cause otoliths to roll and bend hair cells
dynamic equilibrium
sense that reports on the rotatory or angular movements of the head in space
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