Special Senses Flashcards
what is the structure and function of the sclera of the eye?
white of the eye covered by bulbar conjunctive
formed from fibrous and elastic tissue
allows contraction of eye, load bearing and maintains refractive status with the cornea
what is the iris of the eye?
smooth muscle structure controlling pupil diameter
what 2 muscles control the pupil diameter?
sphincter papillae (constriction)
dilator papillae (dilation)
why is the cornea of the eye most used for transplants?
it’s avascular so it’s less likely to reject new tissue
explain the outcome of the optic nerve when brain pressure increases
pressure travels along the optic nerve causing bulging of optic disk (papilloedema)
what is keratoconus?
thinning of the cornea causing a cone shaped cornea and vision blurring
what happens in the anterior and posterior chamber of the eye?
produces humerus fluid and circulates it between anterior and posterior to maintain eye pressure
explain the function of the lens of the eye
helps focus visual info to the back of the retina
describe the composition of the vitreous chamber
contains vitreous humour, a gel like structure
contains phagocytes to remove cell debris
composed of water/electrolytes
no blood vessels
explain the function of the retina
interpretates black and white vision (rods) and coloured vision (cones)
explain the journey of the impulses of vision from eye to brain
optic nerve -> optic chiasm -> optic tract -> radiation -> occipital lobe of brain
where does tear production occur?
lacrimal gland
what are the functions of tears?
lubricates movement
removes debris (washed across eye from lateral to medial)
what are the 7 bones of the orbit?
frontal, sphenoid, zygomatic, palatine, ethmoid, lacrimal, maxilla
what are the 3 sinal cavities?
orbital, nasal and oral cavities
what are the 4 types of paranasal sinuses?
maxillary (under eyes)
frontal (forehead)
ethmoid/sphenoid (posterior to nose)
what is the function of sinuses?
mucous circulation
contributes to sound resonance
reduces skull weight
what is the function of extraocular muscles?
repsonsible for movement of the eye structures
name the 7 extraocular muscles and which cranial nerve innervates it
levator palpebrae superioris (CN3)
superior rectus (CN3)
inferior rectus (CN3)
medial rectus (CN3)
lateral rectus (CN6)
superior oblique (CN4)
inferior oblique (CN3)
what is the function of the levator palpebrae superioris muscle?
keeping upper eyelid open
what is the function of the medial and lateral rectus muscles?
medial - adducts eyeball (towards nose)
lateral - abducts eyeball (away from nose)
what is the function of the superior/inferior rectus muscles?
superior - elevation of eyeball (up/towards nose)
inferior - depression of eyeball (down/towards nose)
what is the function of the superior/inferior oblique muscles?
superior - depression of eyeball (down/away from nose)
inferior - elevation of eyeball (up/away from nose)
how does the nose control the features of the air entering?
rich/superficial blood supply to warm air
mucous provides moisture to air
mucous and hair traps patricles to filter air
what is the purpose of the olfactory nerve?
converts chemical energy to electrical energy
located in superior surface of nasal cavity
what are the folds in the nasal cavity called and what is their function?
conchae - increase surface area and increase chance of olfactory exposure
name 2 unusual characteristics of the tongue muscle
boneless
contains both intrinsic and extrinsic muscle
what are the 2 parts of the tongue?
oral - at front
pharyngeal - at back
what are the sublingual glands?
salivary glands producing mucous like secretion
name the 2 surfaces within the mouth
buccal - cheek
lingual - inner gums
what is the muscle at the bottom of the mouth?
mylohyoid muscle
name the 6 structures of the tongue
foramen caecum
terminal sulcus
foliate papillae
fungiform papillae
vallate papillae
filiform papillae
name the nerve innervating the front 2/3 of the tongue and the 2 nerve branches which combine to form it
lingual nerve
formed from chorda tympani (from CN7) and 3rd branch of CN5
what functions do cranial nerves 9 and 12 have in the back 1/3 of the tongue
CN9 carries taste and sensation
CN12 allows motor control
what strucures are found in the external ear?
ear drum/tympanic membrane
what structures are present in the middle ear?
malleus/incus/stapes bones
oval window
what features are found in the inner ear?
semicircular canal
cochlear
what cranial nerves are found in the internal acoustic meatus’?
CN7 and CN8
what are the 2 portions of the temporal bone?
petrous and squamous
what is the function of the ossicles?
transmit vibrations through middle ear
what is found in the lateral wall of the middle ear?
tympanic membrane (ear drum)
what is found in the medial wall of the middle ear?
vestibular window - opening into vestibule of inner ear, closed by stapes base
cochlear window - opening into cochlear portion of inner ear
what is the function of the cochlea?
sound amplification, conversion from vibration to electrical signal, signal transferred through CN8
what is the function of the semicircular canals?
balance, innervated by CN8 (vestibular part)
what does the auditory (eustachian) tube do?
links middle ear with pharynx to maintain pressure
explain sound waves
vibration of a medium
spreads out as a pressure wave
name the measurements for different aspects of sound
frequency - hertz
intensity (loudness) - decibels
name the basic structures in each section of the ear
outer - pinna, canal
middle - tympanic membrane, ossicles
inner - cochlea, vestibules
what is the function of the pinna?
amplifies & filters incoming sounds (directional dependant)
how does the middle ear overcome impedance mismatch?
collects sound over large area (tympanic membrane)
converts air vibration into bone vibration (dense)
concentrates energy onto small area (oval window)
uses bone as piston to transfer energy in fluid
what is the main advantage of a 3 ossicle system?
increased high frequency range
what are the 2 protective muscles of the middle ear?
stapedius reflex and tensor tympani
when does the eustachian tube open?
during swallowing and valsalva (ear popping)
name some reasons for conductive hearing loss
canal - wax, foreign body
tympanic membrane - perforation
ossicles - congenital fusion, infection damage
middle ear - fluid instead of air
what structural feature of the ear allows amplification?
the tympanic membrane being much larger than oval window
how do vibrations enter the cochlea?
oval window faces into vestibule
vestibule contains sensory epithelia for saccule/utricle
vestibule leads into scala vestibuli (upper cochlear duct)
explain the structure of the organ of corti
sits on basilar membrane, connected to auditory nerve fibres, contains spiral ganglion
how does the basilar membrane contribute to frequency analysis?
stiff and light at one end but flexible and heavy at another end
explain the hair cell structure in the cochlea
hair cells of epithelial origin (resembling stomach cells)
stereocilia form bundles at atypical pole of hair cell
arranged from shortest to tallest
explain how stereocilia contribute to membrane polarisation
if stereocilia pushes towards tallest hair cells -> depolarisation and K+ channels open into endolymph
vice versa
what do inner hair cells do?
turn vibrations into neural signals
name some things that in the inner ear that can cause hearing loss
loss of inner hair cells (no signal to brain)
loss of outer hair cells (basilar vibration impaired)
what fluid is contained in the scala media and what is unique about it?
endolymph - high potassium and low sodium
what fluid is contained in the scala vestibuli/tympani?
perilymph
what is the function of the stria vascularis?
regulates ionic and metabolic functions of scala media
how do outer hair cells (OHCs) amplify vibration?
when stimulated (basilar membrane movement) they change shape/stiffness
feeding energy into BM which acts as an amplifier (increases BM total vibration)
how does the nose conduct quiet breathing?
laminar airflow over the inferior turbinate
what does sniffing do in terms of odorants?
mixes air and sends odorants towards roof of nose towards olfactory receptors
explain the function of odorants being detected by olfactory receptors
odorant molecules dissolved in nasal mucous which is then detected by rhodopsin
what feature of odorants and receptors have that allows smell identification?
odorants can stimulate more than one receptor and receptors can respond to more than 1 odorant
where does the olfactory nerve project to?
amygdala, hippocampus, parahippocampal gyrus
what surgeries can loss of taste be a side effect of?
ear/salivary gland surgeries
