HUMAN ANATOMY: Special Senses

special senses receptor types

chemoreceptors, mechanoreceptors, and photoreceptors

special senses

smell, taste, hearing & equilibrium (balance), and sight

chemoreceptors

smell & taste

mechanoreceptors

hearing & equilibrium

photoreceptors

sight

olfaction

smell

where are the olfactory chemoreceptors?

pseudostratified ciliated columnar epithelium

olfactory bulbs

location where chemoreceptors synapse with interneurons; part of the CNS

pathway of olfactory reception

mucus traps molecules from inhaled air => olfactory receptors are activated => like molecules synapse in a glomerulus => activated interneurons send signal through the olfactory tract to the olfactory cortex

papilla that contain taste buds

vallate (circumvallate) papilla and fungiform papilla

filiform papillae

create the rough texture of the tongue as they allow it to grip food; no tastebuds

taste bud

composed of: 50-100 cells, a taste pore, gustatory receptor cells with hair, supporting cells, and basal cell

gustatory receptor cells w/ hair (tastebud)

respond to chemicals in food and drink

supporting cells (tastebud)

insulatory and make up half of all cells

basal cells (tastebud)

immature cells that replace old/ damaged cells every 7-10 days

axons (tastebud)

taste fibers of cranial nerve; transport signal from gustatory receptor cells to CNS

taste pore

place when dissolved molecules/chemicals and saliva are presented

gustatory receptor cells

these cells are activated once the microvillus (hair) comes in contact with the molecules from the taste pore

flavor

combination of taste, smell, and texture

vision

our most dominant sense; where 70% of all sensory receptors are located

iris

colored portion of the eye made up of smooth muscle; contracts/enlarges the pupil to let in light entering the eye and contains melanocytes

pupil

hole within the iris that can change the diameter

sclera

white of eye that wraps around the entire eye and gives the eye its shape, extension of dura mater; dense irregular CT

eyelid

palpebra

palpebral fissure

opening created when eyelid is up

lacrimal gland

one per eye; serous cell that produces tears, fluid washes away irritants from surface of eye

draining of lacrimal gland

lacrimal canaliculi => lacrimal sac => nasolacrimal duct => nasal cavity

extrinsic eye muscles

six per eye that coordinate eye movement; attach to sclera

strabismus

misaligned eyes “cross eyed”; when extrinsic muscles don’t function the way they should which can result in double vision, lack of stereoscopic vision, and amblyopia

stereoscopic vision

the ability for the brain to register three dimensional objects

amblyopia

reduced vision in the waker or “lazy” eye

fibrous tunic

the avascular outer layer of the eye (extension of dura mater) that provides protection and mechanical support; consists of the sclera and cornea

cornea

transparent part of the eye that covers the iris and the pupil and allows light to enter the inside; parallel collagen fibers/ dense regular CT

conjunctiva

covers the sclera and is where the blood vessels sit

conjunctivitis

pink eye

vascular tunic

lines the inner surface of the sclera and made up of three major parts: choroid, iris, and ciliary body

choroid

vascular, dark surface that absorbs excess light

melanocytes

brown pigment that determines eye color

ciliary body

smooth muscle that controls the shape of the lens, which focuses light on the back surface of the eye; capillaries within produce the aqueous humor

aqueous humor

produced by the ciliary body and circulates through the anterior segment of the eye; behaves as the CSF in the eye

glaucoma

condition where aqueous humor is drained slower than its produced increasing pressure within the eye and damaging the retina

sensory tunic

innermost layer of the eye composed of the retina

retina

structure in the eye composed of the pigmented and neural layers; nerve tissue at the back of the eye that receive images and sends them as electric signals through the optic nerve to the brain

pigmented layer

single epithelial layer within the retina that contains melanin granules that lies against the choroid; absorbs light and nourishes the neural layer

neural layer

layer within the retina that is in contact with the lumen of the eye and contains three type of neural cells; photoreceptor cells, bipolar cells, and ganglion cells

rod cells

type of photoreceptor in the retina; most numerous and most sensitive to light (good for low light) side of eye

cone cells

type of photoreceptor in the retina; works best in bright light and has three subtypes (blue, red, green) back of eye

bipolar cells

cells in the retina that are activated by cones and rods

ganglian cells

cells in the retina that are activated by bipolar cells and transmit impulse to the brain through the optic nerve

what type of cells are utilized when eyes are adjusting from a light room to a dark room

cones and rods

optic disc/blind spot

location at the back of the eye where axons of the ganglion cells are leaving the eye; lack of cones and rods

macula lutea

region at the posterior pole of the eye where light comes in directly giving you the best possible visual of an object whilst looking directly at it in good light conditions; fovea centralis and mostly cones

fovea centralis

the very center of the macula lutea composed of cones completely and gives maximum visual acuity

lens

concentric layers of fibers suspended in the ciliary body that separates the anterior and posterior segments of the eye; changes shape to focus light

emmetropic eye

normal eye; light focuses on retina

myopic eye

nearsighted eye as the light focuses on the front of the retina; concave lens

hyperopic eye

farsighted eye as light focuses behind the retina; convex lens

presbyopia

lens becomes less elastic as we age

LASIK surgery

surface of the cornea is reshaped using a laser in order to properly redirect light onto the retina

astigmatism

abnormal shape of cornea surface causes light rate to scatter differently resulting in two or more focal points

anterior segment of the eye

segment that exists between the cornea and lens containing aqueous humor; supplies nutrients/oxygen to the lens and cornea, blood filtrate from ciliary body, and removed at scleral venous sinus

posterior segment of the eye

segment that exists behind the lens containing the vitreous humorl holds everything into place

vitreous humor

thick fluid of the posterior segment that supports the lens and retina and is composed of 98% water as well as collagen

detached retina

a hole or small tear in the retina that peels retina from choroid later and leaks vitreous humor in the retina causing photoreceptors to die

sensory functions of the ear

hearing and equilibrium

external ear

region of the ear that collects and directs sound waves

middle ear

region of the ear that amplifies and transmits sound waves; air filled cavity

inner ear

sensory organs for hearing and equilibrium; fluid filled cavity

auricle (pinna)

structure of the external ear; outer fleshy portion of the ear that provides protection and funnels sound

external acoustic meatus

structure of the the external ear; air filled canal lined with stratified squamous epithelium

ceruminous glands

glands within the external acoustic meatus that secrete cerumen (wax) which inhibits microorganism growth

tympanic membrane (eardrum)

structure that separates the external (skin lining) and middle ear (mucous membrane lining); vibrates when hit by sound waves

perforated eardrum

membrane will heal but scar tissue can affect hearing

auditory ossicles

structure of the middle ear; small bones that transmit vibration from tympanic membrane towards inner ear (malleus, incus, stapes)

pharyngotympanic tube

equalizes pressure with outside air; connects middle ear to nasopharynx

pathway of vibration (middle ear)

tympanic membrane => malleus => incus => stapes => oval window

tensor tympani

small muscle that attaches to malleus that tenses up to control strong vibrations that could damage receptors in inner ear

stapedius

small muscle that attaches to stapes that tenses up to control strong vibrations that could damage receptors in inner ear

oval window

structure of the middle ear; “entrance” for sound vibrations to the inner ear

round window

structure of the middle ear; “exit” for sound vibrations from the inner ear

bony labyrinth

cavity where all inner ear structures are located containing the perilymph (like CSF) and the regions of the: cochlea, vestibule, and semicircular canals

membranous labyrinth of the inner ear

water balloon like structure that contains endolymph with these regions floating within: cochlear duct (sound) and utricle, saccule, and semicircular ducts (equilibrium)

perilymph

bony labyrinth

endolymph

membranous labyrinth

pathway of vibration through the cochlea

oval window => scala vestibule (perilymph) => scala media (endolymph) => crosses basilar membrane (sound receptors) into scala tympani (perilymph) => round window

scala vestibuli

perilymph

scala media

endolymph

basilar membrane

sound receptors

scala tympani

perilymph

spinal organ of corti (membranous labyrinth of the inner ear)

region of cochlear duct with simple columnar epithelium that contains receptor cells; sits on basilar membrane

hair cells (spinal organ of corti)

mechanoreceptor cells that are suspended between the tectorial and basilar membrane

hairs/sterocilia (spinal organ of corti)

organelles of hair cells that initiate an electrical impulse when bent

tectorial membrane (spinal organ of corti)

rigid sheet of collagen fibers that stereocilia are embedded within

fibers of cochlear nerve (spinal organ of corti)

sensory neuros

supporting cells (spinal organ of corti)

protection and support

how does the impulse of the spinal organ of corti work

the basilar membrane vibrates when sound passes from the scala media to scala tympania; hairs between the basilar and tectorial membrane bend generating an impulse

is higher frequency closes to the oval window or cochlear duct

oval window

is lower frequency closes to the oval window or cochlear duct

cochlear duct

bony vestibule

made up of the membranous structures of the utricle and saccule; equilibrium

utricle

responds to acceleration in horizontal direction