Topic 20: Special Senses Flashcards
what is an eye?
-3 layered sphere filled with fluid
what are the structural features of the eye?
-fibrous tunic
-vascular tunic
-nervous (sensory) tunic
-lens
-anterior segment
-posterior segment
what are the parts of the fibrous tunic?
sclera
-cornea
-conjunctiva
what are the characteristics of the sclera?
-white
-avascular CT
what are the characteristics of the cornea?
-transparent
-allows light to pass through
-superficial
-avascular CT
what is the purpose of the cornea being avascular?
-vessels are not in the way of light
what are the characteristics of the conjunctiva?
-covers the anterior sclera
-vascular mucous membrane
-creates bloodshot eyes when the vessels dilate
what are the parts of the vascular tunic?
-choroid (posterior)
-ciliary body (anterior)
-iris
-pupil
what is the choroid?
-contains melanin so that light does reflect back out of the eye
-highly vascular
-posterior
what is the ciliary body?
-ciliary muscle + cilliary processes
-focuses the lens
what is the iris?
-coloured part of the eye
-what is the pupil?
-hole in the iris
what is the nervous (sensory) tunic?
-retina of the eye
what are the parts of the nervous (sensory) tunic?
-outer pigmented layer
-inner neural layer
-fovea centralis
-optic disc
what is the inner neural layer?
-3 layers of neurons
-photoreceptors
-bipolar cells
-ganglion cells (axons from optic nerve (cranial nerve II)
what are the 2 types of photoreceptors in the inner neural layer?
-rods = allow to see black + white
-cones = allow to see colour
what is the fovea centralis?
-where light is focused
-area of greatest visual resolution (acuity) (sharpness)
-no rods, only cones
what is the optic disc?
-blind spot where blood vessels + optic nerve exit the eye
-no rods, or cones
what are the characteristics of the lens of the eye?
-avascular
-transparent
what are cataracts?
-cloudy areas in the lens
what is the anterior segment?
-anterior to the lens
-contains aqueous humour (fluid similar to plasma)
what is the posterior segment?
-posterior to the lens
-contains vitreous humor (gel-like substance)
what are the structural features of the ear?
-external ear
-middle ear
-inner ear (labyrinth)
-cochlea
-receptors in the inner ear
what is the function of the external ear, middle ear, and inner ear?
-all conduct sound
what are the parts of the external ear?
-auricle (pinna)
-external auditory canal (meatus)
-tympanic membrane (eardrum)
what is the auricle made of?
-elastic cartilage covered with skin
-body of the ear
what are the parts of the middle ear?
-eustachian tube
-ear ossicles
what is the eustachian tube also called?
-pharyngotympanic tube
what are the 3 ear ossicles?
-malleus
-incus
-stapes
what is the malleus secured to?
-the tympanic membrane
how does the stapes transmit sound to the inner ear?
-via the oval window
what are the parts of the inner ear?
-bony labyrinth
-membranous labyrinth
what is the bony labyrinth?
-tunnels in the temporal bone
-tunnels contain perilymph
-contains the semicircular canals, vestibule, and cochlea
what are the semicircular canals + the vestibule of the bony labyrinth used for?
-sound equilibrium
what is the cochlea used for?
-hearing
what is the membranous labyrinth?
-surrounded and protected by the bony labyrinth
-contains endolymph
-3 parts, semicircular duct, utricle + saccule, cochlear duct
where is the semicircular duct located?
-inside the canals
where are the utricle + saccule located?
-inside the vestibule
where is the cochlear duct located?
-inside the cochlea
what is the cochlea?
-coiled canal
what are the 3 channels of the cochlea? where are they located? what fluid is present?
-scala vestibuli = upper = perilymph
-scala tympani = lower = perilymph
-cochlear duct = middle = endolymph
what are the 3 membranes of the cochlea? where are they located or what do they cover?
-vestibular membrane = between cochlear duct + scala vestibuli
-basilar membrane = between cochlear duct + scala tympani
-tectorial membrane = covers hair cells (receptor cells)
what are the receptors in the inner ear?
-hair cells that synapse with neurons
-cilia
what do the hair cells do as receptors?
-send impulses to the brain via cranial nerve VIII
where are the tips of the cilia embedded? what does this allow for?
-the tectorial membrane
-allows for stability
