Topic 20: Special Senses

Question 1

what is an eye?

Answer 1

-3 layered sphere filled with fluid

Question 2

what are the structural features of the eye?

Answer 2

-fibrous tunic
-vascular tunic
-nervous (sensory) tunic
-lens
-anterior segment
-posterior segment

Question 3

what are the parts of the fibrous tunic?

Answer 3

sclera
-cornea
-conjunctiva

Question 4

what are the characteristics of the sclera?

Answer 4

-white
-avascular CT

Question 5

what are the characteristics of the cornea?

Answer 5

-transparent
-allows light to pass through
-superficial
-avascular CT

Question 6

what is the purpose of the cornea being avascular?

Answer 6

-vessels are not in the way of light

Question 7

what are the characteristics of the conjunctiva?

Answer 7

-covers the anterior sclera
-vascular mucous membrane
-creates bloodshot eyes when the vessels dilate

Question 8

what are the parts of the vascular tunic?

Answer 8

-choroid (posterior)
-ciliary body (anterior)
-iris
-pupil

Question 9

what is the choroid?

Answer 9

-contains melanin so that light does reflect back out of the eye
-highly vascular
-posterior

Question 10

what is the ciliary body?

Answer 10

-ciliary muscle + cilliary processes
-focuses the lens

Question 11

what is the iris?

Answer 11

-coloured part of the eye

Question 12

-what is the pupil?

Answer 12

-hole in the iris

Question 13

what is the nervous (sensory) tunic?

Answer 13

-retina of the eye

Question 14

what are the parts of the nervous (sensory) tunic?

Answer 14

-outer pigmented layer
-inner neural layer
-fovea centralis
-optic disc

Question 15

what is the inner neural layer?

Answer 15

-3 layers of neurons
-photoreceptors
-bipolar cells
-ganglion cells (axons from optic nerve (cranial nerve II)

Question 16

what are the 2 types of photoreceptors in the inner neural layer?

Answer 16

-rods = allow to see black + white
-cones = allow to see colour

Question 17

what is the fovea centralis?

Answer 17

-where light is focused
-area of greatest visual resolution (acuity) (sharpness)
-no rods, only cones

Question 18

what is the optic disc?

Answer 18

-blind spot where blood vessels + optic nerve exit the eye
-no rods, or cones

Question 19

what are the characteristics of the lens of the eye?

Answer 19

-avascular
-transparent

Question 20

what are cataracts?

Answer 20

-cloudy areas in the lens

Question 21

what is the anterior segment?

Answer 21

-anterior to the lens
-contains aqueous humour (fluid similar to plasma)

Question 22

what is the posterior segment?

Answer 22

-posterior to the lens
-contains vitreous humor (gel-like substance)

Question 23

what are the structural features of the ear?

Answer 23

-external ear
-middle ear
-inner ear (labyrinth)
-cochlea
-receptors in the inner ear

Question 24

what is the function of the external ear, middle ear, and inner ear?

Answer 24

-all conduct sound

Question 25

what are the parts of the external ear?

Answer 25

-auricle (pinna) -external auditory canal (meatus) -tympanic membrane (eardrum)

Question 26

what is the auricle made of?

Answer 26

-elastic cartilage covered with skin -body of the ear

Question 27

what are the parts of the middle ear?

Answer 27

-eustachian tube -ear ossicles

Question 28

what is the eustachian tube also called?

Answer 28

-pharyngotympanic tube

Question 29

what are the 3 ear ossicles?

Answer 29

-malleus -incus -stapes

Question 30

what is the malleus secured to?

Answer 30

-the tympanic membrane

Question 31

how does the stapes transmit sound to the inner ear?

Answer 31

-via the oval window

Question 32

what are the parts of the inner ear?

Answer 32

-bony labyrinth -membranous labyrinth

Question 33

what is the bony labyrinth?

Answer 33

-tunnels in the temporal bone -tunnels contain perilymph -contains the semicircular canals, vestibule, and cochlea

Question 34

what are the semicircular canals + the vestibule of the bony labyrinth used for?

Answer 34

-sound equilibrium

Question 35

what is the cochlea used for?

Answer 35

-hearing

Question 36

what is the membranous labyrinth?

Answer 36

-surrounded and protected by the bony labyrinth -contains endolymph -3 parts, semicircular duct, utricle + saccule, cochlear duct

Question 37

where is the semicircular duct located?

Answer 37

-inside the canals

Question 38

where are the utricle + saccule located?

Answer 38

-inside the vestibule

Question 39

where is the cochlear duct located?

Answer 39

-inside the cochlea

Question 40

what is the cochlea?

Answer 40

-coiled canal

Question 41

what are the 3 channels of the cochlea? where are they located? what fluid is present?

Answer 41

-scala vestibuli = upper = perilymph -scala tympani = lower = perilymph -cochlear duct = middle = endolymph

Question 42

what are the 3 membranes of the cochlea? where are they located or what do they cover?

Answer 42

-vestibular membrane = between cochlear duct + scala vestibuli -basilar membrane = between cochlear duct + scala tympani -tectorial membrane = covers hair cells (receptor cells)

Question 43

what are the receptors in the inner ear?

Answer 43

-hair cells that synapse with neurons -cilia

Question 44

what do the hair cells do as receptors?

Answer 44

-send impulses to the brain via cranial nerve VIII

Question 45

where are the tips of the cilia embedded? what does this allow for?

Answer 45

-the tectorial membrane -allows for stability