SPECIAL SENSES Flashcards
What is the cranial nerve of smell
olfactory nerve (CN 1)
sensory
What is the cranial nerve of sight
Optic nerve (CN 2)
sensory
What is the cranial nerve of hearing
vestibulocochlear nerve (CN 8)
sensory
What are the cranial nerves of taste
Facial nerve (CN 7) sensory and motor
Glossopharyngeal nerve (CN 9) sensory and motor
what cells secrete mucous
respiratory type epithelium cells which contain seromucus glands
What are the borders of the nasal cavity
external/anterior openings = nares
posterior openings = choanae
medial wall = septum
lateral walls = cartilage and cranial bones (conchae and meatus)
floor = hard palate
roof = cranial bones + olfactory region
Explain the nerves of smell
Olfactory nerve fibres and receptors in olfactory epithelium pass into cranial bones to olfactory bulbs
bulbs become olfactory nerve tracts (CN 1) and project to olfactory cortex of temporal lobe
What is the orbit
bony cavity for eye made of 7 cranial bones.
orbicularis oculi: circular muscles that close eyelids
extra ocular muscles: move eye and open eyelid
lacrimal apparatus: production, drainage of fluid from eye (tears)
List the parts of the eye
Cornea conjunctiva iris lens anterior and posterior cavities
Outline the cornea
refracts bends light
anterior and posterior surfaces are epithelium
anterior surface continuous with conjunctiva
avascular
Outline the conjunctiva
Provides mechanical protection and lubrication
epithelium, secretory cells, fibrous tissue and blood vessels.
covers posterior surface of eyelids and reflects to cover anterior surface of eyeball
extends over the anterior sclera
Outline the iris
Regulates amount of light entering eye
thin diaphragm of tissue on lens
sphincter papillae arranged circularly around pupil, constrict, parasympathetic
dilator papillae arranged radially, dilate, sympathetic
Outline the lens
Refracts/bends light onto retina to focus on images
avascular biconvex disc
CT capsule
suspensory ligaments anchor edges of lens to ciliary smooth muscles which contract to adjust lens
parasympathetic
flatter = distant rounder = closer
Outline anterior cavity
Anterior: contains fluid aqueous humor and supplies nutrients to avascular cornea and lens
maintains intraocular pressure ans shape of anterior eye
fluid continuously produced
Outline posterior cavity
Gelatinous mass called vitreous humor
Formed in development, not replaced
Stabilises shape of eye due to muscles
Outline the layers of the eye
fibrous tunic (sclera, white of eyes): protects eye, muscle attachment
vascular tunic (choroid): vascularised, smooth muscles of ciliary and iris, blood vessels enter at optic nerve to supply retina/pupils/lens
Neural tunic: explained in another
Describe the neural tunic (retina)
innermost, avascular
macula: all cones, no rods
fovea: within macula, densest conc of cones
optic disc: where optic nerve attaches to eye
What are the photoreceptors of the eye
rods: sensitive to light, night, no colour distinction
cones: red, green and blue, require light to function
Explain the nerves of sight
Visual info of photoreceptors sent to optic nerve, then primary visual cortex of occipital lobe.
partial decussation at optic chiasm
Describe the outer ear
auricle/pinna: funnels sound into the auditory meatus
external auditory meatus/acoustic canal: traps foreign particles a by hair cells and ceruminous glands which secrete ear eax. Protect tympanic membrane
Tympanic membrane: Lateral side epidermis, medial side thin mucous membrane, separate external and middle ear
Describe the middle ear
Tympanic cavity: contains oval window
pharyngotympanic tube: opens to equilibrate pressure in cavity with outside
auditory ossicles: amplify sound. malleus, incus, stapes. connect to tympanic membrane and oval window. skeletal muscles prevent excessive movement
Describe the internal ear
Oval window: connects to series of cavities like bony labyrinth
Bony labyrinth: vestibule, three semicircular canals and cochlea, lined with periosteum
Membranous labyrinth: suspended within the fluid, cochlear duct
Cochlea and cochlear duct: in another
Describe the cochlea and cochlear duct
cochlea: transduces sound, curls, contains clear lymphatic fluid and cochlear duct
cochlear duct: contains hair cells/stereocilia, clear lymphatic fluid
explain the nerves and physiology of hearing
Auricle directs sound into auditory meatus
Waves hit tympanic membrane converting sound to mechanical movement
Ossicles movement cause vibration of oval window
Oval window vibration generates wave in lymphatic fluid, travels through cochlea
Waves bend stereocilia which are detected by receptors of the cochlear nerve fibres
Cochlear nerve branch of vestibulocochlear nerve that sends info to primary auditory cortex
Describe the 4 papillae of the tongue
Vallate/circumvallate: largest, V-shaped
line anterior to the terminal groove. many receptors
Foliate: folds on lateral surfaces of tongue anterior to terminal groove. few receptors
Fungiform: small, found on dorsum of tongue. Some receptors
Filiform: smallest, cone-shaped projections. No receptors
What are the receptors of the tongue papillae
Gustatory receptors
What are the 5 tastes
sweet salty sour bitter umami
Outline the nerves involved in taste
Gustatory receptors project to facial nerve for the body of tongue (anterior 2/3) and glossopharyngeal nerve for the root of tongue (posterior 1/3). Project to gustatory cortex
