Unit 14 The Special Senses.docx

8/18/2019 Unit 14 The Special Senses.docx

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UNIT 14: THE SPECIAL SENSES

1. List the special sense organsEye, Ear, Nose, Tonge

!. I"enti#y the general $so%atic& sense organs: $p.!''&

(ree ner)e en"ings $pain an" te%peratre receptors&

Tactile $*eissner& corpscles $toch receptor&

+los $-##ini& corpscles

La%ellar $Pacinian& corpscles $"eep pressre receptor&

En"ls $/rase corpscles&

0olgi ten"on receptors $proprioceptor&

*scle spin"les $proprioceptor&


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THE EE'. I"enti#y an" "escrie the accessory organs o# the eye accor"ing to:

Con2ncti)a lines the eyelids and covers part of the outer surface of the eyeball.It ends at the edge of the cornea by fusing with the corneal epithelium. The

conjunctiva secretes mucus, which helps to lubricate the eyeball and keep itmoist.

Eyeli"s Anteriorly the eyes are protected by the eyeli"s, which meet at themedial and lateral corners of the eye

E3trinsic eye %scles are attached to the outer surface of each eye. Extrinsic eyemuscles aim the eyes for following moving objects and for convergence.

Lacri%al apparats The lacri%al apparats consists of the lacrimal gland anda number of ducts that drain the lacrimal secretions into the nasal cavity.

Lacri%al 0lan"s The lacri%al glan"s are located above the lateral end of eacheye. They continually release a dilute salt solution tears! onto the anteriorsurface of the eyeball through several small ducts.


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*e"ical canths an" lateral canths the medial and lateral corners of the eye

Tarsal $%eio%ian& glan"s *o"i#ie" sebaceous glands associated with theeyelid edges

4. escrie the gross strctre an" #nctions o# the #ollo5ingco%ponents o# the eyeall:

Sclera $oter 5hite layer& "rotective outermost layer, #iros layer , thick,

glistening white connective tissue, is seen anteriorly as the #white of the eye.$

Cornea $#rontal, clear& Transparent, #iros layer

Choroi" $secon" layer, )asclar, n"er sclera& %ost posterior is the choroid, ablood&rich nutritive tunic that contains a dark pigment. The pigment prevents lightfrom scattering inside the eye.

Cilary o"y $%scle& %oving anteriorly, the choroid is modified to form twosmooth muscle structures, the ciliary body

Iris $color in persons eye& The pigmented iris has a rounded opening

Lens The lens is the major light&bending refractory! structure of the eye. Its convexity isincreased by the ciliary body for close focus.

-etina

Anterior cha%er The anterior chamber is the front part of the eyebetween the cornea and the iris.

Posterior cha%er: The posterior chamber is between the iris andthe lens.


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A6eos cha%er The lens divides the eye into two segments, or chambers.The anterior a'ueous! segment, anterior to the lens, contains a clear wateryfluid called a'ueous humor

Posterior cha%er The posterior vitreous! segment, posterior to the lens, is

filled with a gel like substance called either vitreous humor or the vitreous body

7itreos h%or (itreous humor helps prevent the eyeball from

collapsing inward by reinforcing it internally. The vitreous chamberis between the lens and the back of the eye.

8ptic "isc $lin" spots& The blind spot optic disc! is the point where the opticnerve leaves the back of the eye

ball.

8ptic ner)e


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9. escrie the %icroscopic strctre o# the retina n"er the #ollo5inghea"ings: $p.!'!9&

Pig%ent layer

Neral layer

o Photoreceptor cellso +ipolar cells

o 0anglion cells

-o"s The rods are most dense at the periphery, or edge, of the retina and decrease innumber as the center of the retina is approached. The rods allow us to see in gray tonesin dim light, and they provide our peripheral vision.

Cones Cones are discriminatory receptors that allow us to see the details of our worldin color under bright light conditions. They are densest in the center of the retina anddecrease in number toward the retinal edge.

*ascla ltea It is the part of the retina that is responsible for sharp, detailedcentral vision also called visual acuity!. The %acla ltea, also called fovea,contains a very high concentration of cones, the light&sensitive cells in the retinathat give detailed central vision.

(o)ea centralis lateral to each blind spot is the fovea centralis, a tiny pit thatcontains only cones. )onse'uently, this is the area of greatest visual acuity, orpoint of sharpest vision, and anything we wish to view critically is focused on thefovea centralis

;. Locate the )isal corte3 $p.!4


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The external acoustic meatus or auditory canal! is a short, narrow chamber about +inch long by +- inch wide! carved into the temporal bone of the skull.

11.escrie the strctre an" #nction o# the %i""le ear n"er the#ollo5ing hea"ings:

Ty%pan% is a small, air&filled, mucosa&lined cavity within the temporal bone. It isflanked laterally by the eardrum and medially by a bony wall with two openings, the ovalwindow and the inferior, membrane covered round window

8ssicles: %alles, incs, stapes The tympanic cavity is spanned by the three smallestbones in the body, which transmit the vibratory motion of the eardrum to the fluids of the inner

ear

*alles $ha%%er& When the eardrum moves, the hammer moves with it and transfers thevibration to the anvil

Incs $an)il& The anvil, passes the vibration on to the stirrup, which presses on the ovalwindow of the inner ear.

Stapes $stirrp&

8)al 5in"o5

-on" 5in"o5

A"itory $pharyngoty%panic& te runs obli'uely downward to link the middleear cavity with the throat, and the mucosae lining the two regions are continuous.

ormally, the pharyngotympanic tube is flattened and closed, but swallowing oryawning can open it briefly to e'uali/e the pressure in the middle ear cavity withthe external, or atmospheric, pressure. This is an important function because theeardrum does not vibrate freely unless the pressure on both of its surfaces is thesame. 0hen the pressures are une'ual, the eardrum bulges inward or outward,causing hearing difficulty voices may sound far away! and sometimes earaches.The ear&popping sensation of the pressures e'uali/ing is familiar to anyone whohas flown in an airplane.

1!.escrie the strctre an" #nctions o# the inner ear:

+ony or osseos layrinth The bony labyrinth is filled with plasma like fluidcalled perilymph

o Perily%ph also known as )otunnius1 li'uid, and li'uor

cotunnii! is an extracellular fluid located within the cochleapart of the inner ear! in two of its three compartments2 thescala tympani and scala vestibuli. The ionic composition of


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perily%ph is comparable to that of plasma andcerebrospinal fluid.

*e%ranos layrinth 3uspended in the perilymph is a membranous labyrinth,a system of membrane sacs that more or less follows the shape of the bony

labyrinth. The membranous labyrinth itself contains a thicker fluid calledendolymph

o En"oly%ph 4luid waves occur in the en"oly%ph in the

various parts of the membranous labyrinth in response tofluid waves in the perilymph.

1'.List the three "i)isions o# the ony an" %e%ranos layrinthCochlea

Se%icirclar canals an" "cts

7estile The vestibule is situated between the semicircular canals and the cochlea.


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14.escrie 5hich parts o# the inner ear #nction in:

Static E6iliri%

yna%ic E6iliri%

Hearing

19.escrie the asis #or ho5 the strctres o# the %i""le ear an" inner ear #nction

The *i""le ear structures are the ossicles and pharyngotympanic tube withinthe tympanic cavity. Auditory ossicles transmit the vibratory motion from theeardrum to the oval window. The pharyngotympanic tube allows pressure to bee'uali/ed on both sides of the eardrum. These structures are involved withsound transmission only.

The internal ear or bony labyrinth consists of bony chambers cochlea,vestibule, and semi& circular canals! in the temporal bone. The bony labyrinthcontains perilymph and membranous sacs filled with endolymph. 0ithin themembranous sacs of the vestibule and semicircular canals are e'uilibriumreceptors. 5earing receptors are found within the membranes of the cochlea.

1;. e#ine the )estilocochlear $acostic& ner)e $Cranial Ner)e 7III&

The eighth cranial ner)e. e#inition )I! The eighth cranial ner)e composedof the acostic ner)e and the )estilar ner)e. The ner)e travels from the

inner ear, enters the cranial cavity through the internal a"itory foramen and joins the brainstem.

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Unit 14 The Special Senses.docx