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98 terms

Exercise 24: Special Senses

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Palpabrae
eyelids
Conjunctiva
the thin, protective mucous membrane that covers the anterior eye and folds to cover the inner eyelid
Palpebral conjunctiva
covers the interior of the eyelid
Bulbar conjunctival
covers the anterior part of the white of the eye, but not the cornea
Lacrimal apparatus
is a group of structures involved in producing and draining tears
Lacrimal gland
produces and secreates tears onto the eye surface
Lacrimal canals
drain tears from teh eyes into the enlarged lacrimal sac
Lacrimal sac
the lacrimal canals drain tears from the eyes into this sac
Nasolacrimal duct
receives tears from the lacrimal sac and drains the tears into the nasal cavity
Extrinsic eye muscles
aare six skeletal muscles that insert on teh exterior of the eyeball to move the eyeball in all directions: the superior, inferior, medial, and lateral rectus muscles are parallel to the long axis of the eyeball; the superior and inferior oblique muscles attach to the eye ball at an angle
Inferior oblique
moves eye superiorly and laterally
Inferior rectus
moves eye inferiorly
Lateral rectus
moves eye laterally
Medial rectus
moves eye medially
Superior oblique
moves eye inferiorly and laterally
Superior rectus
moves eye superiorly
Wall of the eyeball
has three layers: the outer fibrous tunic, the middle vascular tunic, and the inner retina
Fibrous tunic
is composed of teh cornea and sclera
Cornea
the transparent anterior portion that covers the iris and pupil
Sclera
the touch, white part of the eye that forms the majority of the eyeball
Scleral venous sinus
is an opening found at the junctino of the cornea and sclera; drains aqueous humor back into the bloodstream
Vascular tunic
is composed of the iris, ciliary body, and choroid
Iris
the most anterior portion of the vascular tunic and contains pigmented cells; it is made of circular smoth muscle and controls the pupil size
Pupil
is the opening in teh middle of the iris that allows light to enter the eyeball and changes size in response to teh intensity of light
Ciliary body
begins posterior to teh iris at the junction of the cornea and sclera and consists of the ciliary muscle and ciliary processes
Ciliary muscle
is a circular smooth muscel that ocntracts to control the sape of the lens
Ciliary processes
are folds that protrude from teh ciliary body toward the lens; they contain capillaries that secrete aqueous humor, the fluid in the anterior chamber of the eyeball
Suspensory ligaments
are thin fibers that attach the lens to the ciliary processes
Choroid
is the most posterior part of the vascular tunic that lines most of the interior of the sclera; it contains many blood vessels that nourish teh retina
Retina
is the inner coat that begins at teh ora serrata; the retina continues posteriorly, lining the interior of the choroid; teh pigmented layer of the retina is the outer portion, and the neural layer is the inner portion that contains photoreceptors and associated neurons
Ora serrata
the serrated boundary between the ciliary muscle and the retina
Interior of the eyeball
contains the lens, anterior cavity, and vitreous chamber
Lens
divides the interior of the eyeball into an anterior cavity and a vitreous chamber (posterior cavity)
Anterior cavity
is a space between teh cornea and the lens that is filled with watery aqueous humor; this cavity is subdivided into an anterior chamber and a posterior chamber
Anterior chamber
part of the anterior cavity; between the cornea and the iris
Posterior chamber
part of the anterior cavity; betwen teh iris and the lens
Vitreous chamber
is the larger, posterior cavity located between teh lens and the retina; is filled with a gel-like substance called teh vitreous body (humor) that holds the retina flat agains the choroid
Neural portion of the retina
an outgrowth of the brain and contains three layers of neurons: the photoreceptor layer (deepest cell layer), the bipolar cell layer (middle layer), and the ganglion cell layer (the superficial cell layer)
Photoreceptor cell layer
contains the rods and cones, which synapse with the bipolar neurons in teh bipolar cell layer
Rods
are used in night vision and respond to low levels of light, allowing us to perceive shades of gray, black, and white; visual acuity with rods is low
Cones
require brighter light for stimulation, but allow us to see color and provide high visual acuity
Bipolar cell layer
cells here synapse on the ganglion cells in teh ganglion cell layer
Ganglion cell layer
axions from the ganglion cells extend through the optic disc and leave the eyeball as the optic nerve
Optic disc
does not contain photoreceptors and forms the blind spot of the retina; it is also teh site where the central retinal artery and vein center enter and leave the retina, and the only place where the retina is secured to teh otehr layers of the eyeball
Macula lutea
the site of macular degeneration, is in the center of the neural portion of the retina
Central fovea
in the middle of the macula lutea is this; this area of the retina has the highest density of cones of any area of the retina and is not covered by ganglion and bipolar cell layers; therefore , this area ahs the highest visual acuity of any area of the retina; when we look at an object, the light rays reflected from teh object are focused onto teh central fovea
Ophtalmoscope
the retina can be viewed with this; it illuminates teh interior of the eye
Regions of the ear
the external ear, the middle ear, the internal ear
External ear
consists of the auricle, external auditory canal, and tympanic membrane; extends fromt eh auricle to teh tympanic membrane
Auricle
teh flexible external structure that is commonly called the ear, collects sound waves and directs them toward the external auditory canal
Helix
the rim of the auricle
Lobule
the flesy, inferior portion of the auricle
External auditory canal
conducts sound waves from the auricle to the tympanic membrane
Tympanic membrane
(eardrum) converts sound waves to vibrations that are transferred to middle ear structures
Middle ear
is an air-filled cavity within the temporal bone that extends from teh tympanic membrane to teh oval window; structures include the auditory ossicles, oval window, roudn windown and auditory tube
Auditory ossicles
are small bones within teh cavity that are connected by synovial joints; they transfer vibrations from the tympanic membrane to teh oval window; include the malleus, incus, and stapes
Malleus
the outermost auditory ossicle and is attached to the tympanic membrane
Incus
the middle auditory ossicle and connects to the stapes
Stapes
the innermost auditory ossicle; connects to the incus and teh oval window
Oval window
the membrane-covered opening that separates teh mdidle and inner ear and transfers vibrations to the inner ear
Round window
is a membrane-covered opening between teh middle ear and cohlea
Auditory tube
conects the middle ear to the nasopharynx, and equalizes the air pressure of the ear with atmospheric air
Internal ear
is housed within the temporal bone; it consists of cavities within teh bone called the bony labyrinth that encloses a series of connected membranous sacs, the membranous labyrinth
Bony labyrinth
contains a fluid called perilymph that surrounds the membranous labyrinth; endolymph is the fluid within teh membranous labyrinth; the bony labyrinth has 3 main regions: the vestibule, the semicircular canals, and the cochlea
Vestibule
is the middle area of the bony labyrinth that encircles 2 sections of membranous labyrinth, the utricle and the saccule
Utricle
is the posterior section of the membranous labyrinth within the vesttibule, and is houses equilibrium receptors
Saccule
is the anterior section of the membranous labyrinth within the vestibule; the saccule is continuous with the utircle and also houses equilibrium receptors
Semicircular canals
are 3 bony canals posterior to the vestibule that project posteriorly, laterally, and superiorly from teh vestibule; each canal is at right angles to the other two
Semicircular ducts
are sections of membranous labyrinth within the semicircular canals which contain equilibrium receptors and connects with the utricle
Ampulla
is the widened end of each semicircular canal and duct
Cochlea
the spiral area of teh bony labyrinth anterior to the vestibule; makes 3 turns around a bony cone; a section through this shows 3 channels: the scala vestibuli, teh cochlear duct, and teh scala tympani
Cochlear duct
is teh section of membranous labyrinth within the cochlea; contains the hearing receptors and is connected to teh saccule
Vestibulocochlear nerve
hearing and equilibruim receptors initiate nerve impulses which are carried by this nerve to the brain; has 2 branches: the vestibular branch and the cochlear branch
Vestibular branch
part of the vestibulocochlear nerve; carries nerve nerve impulses generated by equilibrium receptors
Cochlear branch
carries nerve impulses generated by the hearing receptors
Scala vestibuli
is part of the cochlea and is superior to teh cochlear duct; it is separated frmo the cochlear duct by the vestibular membrane; it is continuous with the scala tympani and is filled with perilymph
Scala tympani
is also part of the cochlea and is posterior to cochlear duct; it is separated from teh cochlear duct by the basilar membrane; it is continuous with the scala vestibuli and is filled with perilympth
Cochlear duct
is part of the membranous labyrinth, houses the spiral organ of corti and is filled with endolymph
Spiral organ of Corti
sits on teh basilar membrane; it contains hair cells (receptors for hearing) and supporting cells
Hair cells
have a hair bundle composed of stereocillia at their apical end; superior and in contact with teh stereocilia is the tectorial membrane; the basal end of teh hair cells synapse with sensory and motor neurons from the cochlear branch of the vestibulocochlear nerve
Types of equilibrium receptors
there are 2 types: the maculae and the cristae
Maculae
located in teh utricle and saccule; provide information on head position (static equilibrium), as well as linear acceleration and deceleration, a type of dynamic equilibrium; consists of hair cells with hair bundles and supporting cells
Otolithic membrane
is in contact with teh hair bundles of the maculae; contains calcium carbonate crystals called otoliths
Otoliths
movemtn of the head causes movemetn of the otoliths and otolithic membrane, which bends the hair bundles; the dirrection of movement will determine if the hair cells release more or less neurotransmitter to the associated sensory neurons
Crista
located in teh membranous semicircular ducts within the ampullae; detects rotational accelaeration and deceleration, a type of dynamic equilibrium; each consists of hari cells and supporting cells; the hair bundles of the hair cells are covered by a gelatinous structure called the cupula
Cupula
a gelatinous structure that covers the hair bundles of the hair cells in teh crista; when the head moves, movement of the endolympth pushes the cupula causing the hair cells to bend; bending of the hair bundles results in generation of nerve impulses in the vestibular branch of the vestibulocochlear nerve
Olfactory epithelium
covers teh inferior surface of the cribriform plate, the superior nasal concha, and the upper part of the middle nasal concha; contains olfactory receptors cells, basal stem cells, and ducts of olfactory glands
Olfactory receptor cells
are bipolar neurons whose dentritic end is embedded in the mucus layer covering the surface of the olfactory epithelium and whose axons form the olfactory nerves; they are located on olfactory haris that project from the dentrites of the olfactory receptor cells
Olfactory nerves
pass through the olfactory foramina in the cribriform plate and synapse on neurons in the olfactory bulb; nerve impulses then travel along the olfactory tract to the lateral olfactory area of teh cerebral cortex; olfactory receptors adapt to odors very quickly
Taste buds
are found on the tongue, soft palate, pharynx (throat) and larynx; are microscopic, onion shaped structures that contain gustatory cells, gustatory hairs, and supporting cells
Gustatory cell
each has one gustatory hair that projects through an opening, the taste pore, on the apical end of the taste bud
Gustatory receptors
are located on the gustatory hairs; the basal end of gustatory cells synapse onto the dendritic end of sensory neurons; axons from the sensory neurons contribute fibers to the facial nerve (cranial nerve VII), glossopharyngeal nerve (IX), or vagus nerve (X), depending on the location of the taste bud
Papillae
taste buds on teh tongue are located here; elevated structures that give the tongue its rough appearance; there are 4 types: vallate, fungiform, foliate, and filiform
Vallate papillae
are the largest papillae and form an inverted V at the posterior of the tongue
Fungiform papillae
are mushroom shaped and are scattered over the surface of the tongue
Filiform papillae
are slender, pointed, projections that cover teh surface of the tongue and give the tongue a rough texture; these papillae have tactile receptors but not taste buds; taste buds are found in vallate, fungiform, and foliate papillae
Foliate papillae
are present mostly in children and are lcoated in lateral margins of the tongue
Taste sensations
there are four primary: sweet, bitter, salty, and sour; and a possible fifth, MSG (monosodium glutamate); gustatory receptors most senstive to sweet and salty sensations are found on the tip of the tongue, while bitter sensation are in teh back and sour sensations are on teh sides of the tongue; other taste sensations are a mixture of these four; smell, temperature, and texture (tactile sensation) contribute to our sense of taste