Transcript File

Chapter 14
Seeing and Hearing
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Senses –General and Special
• General
– Visceral sensations
• Hunger, thirst
– Touch
• Touch / tactile, pressure
– Temperature
• Hot/cold
– Pain
• Receptors inside and surface of body
– Proprioception
• Sense of body movement and position
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Special Senses
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(Touch)
Smell
Taste
Vision
Hearing
Equilibrium
• More complex than General senses,
• Sensory structures located in the head
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1. Smell
• Olfactory Sense
• “chemical” sense
• Dogs
– Average of
220 million receptors
– Humans: 5 million
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How do they smell
• Two patches of olfactory epithelial cells
Located up high in both nasal passages
• Odor molecules dissolve in the mucus
nerve impulses are generated that travel to
the brain
• Cranial Nerve I: called Olfactory nerve
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© 2009 Delmar, Cengage Learning
Best Smellers
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Pointers
Coonhounds
English Springer Spaniel
Belgian Malinois
Labrador Retreivers
German Shepherd – 225 million scent receptors
Beagle
Basset Hound
Blood Hound – 300 million scent receptors!
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2. Taste
• Gustatory Sense
• “chemical” sense
• Taste sensations vary from species to
species
Humans taste: sweet sour salty and bitter
Cats do not “taste” sweet
(“tasting” refers to responding to a particular taste sensation)
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Taste Buds
• Tiny rounded structures made
up of gustatory sensory cells
sensory receptors (modified dendrites of neurons)
• Found in elevated papillae around the tongue
• Substance dissolve in saliva, nerve impulses are
generated that travel to the brain
• Cranial Nerve IX (glossopharyngeal nerve)
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3. Equilibrium
• Mechanical sense
• Balance
• Equilibrium works by keeping track of the
position and movement of the head
• Equilibrium receptors are located in portions
of the inner ear (vestibule and semicircular canals)
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4. Hearing
• Auditory Sense
• “mechanical” sense
• Vibrations of air molecules are converted into
nerve impulses that are interpreted by the brain
External Ear
Middle Ear
Inner Ear
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Functions of the Ear
• The ear is the sensory organ that enables
hearing and helps to maintain balance.
• The combining forms for ear are audit/o,
aud/i, and ot/o.
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Outer Ear Structures
• Pinna
– catches and then
transmits sound waves
– Pinn/i is the combining
form.
– Aur/i and aur/o also
mean external ear.
• External auditory
canal
– tube that transmits sound
from the pinna to the
tympanic membrane
– Glands secrete cerumen
here.
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Middle Ear Structures
• Auditory ossicles
– malleus, incus, and
stapes
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Middle Ear Structures
• Tympanic
membrane
– “eardrum”
– Transmits sound waves
to the ossicles
– Tympan/o and myring/o
mean eardrum.
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Middle Ear Structures
• Eustachian tube
– equalizes air and middle
ear pressure
• Tympanic bulla
– osseous chamber that
houses the middle ear
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Inner Ear Structures
• Bony labyrinth
– vestibule
• balance and equilibrium
– semicircular canals
• three canals that regulate equilibrium
– cochlea
• organ of hearing
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Pathological conditions
• Vestibular Disease / Old Dog Vestibular Syndrome
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Equilibrium
Vestibular Cranial Nerve
Possible inner ear infection
Ideopathic
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Deafness and “white” hair
Vibrations occur and the hair cells in the Cochlea move.
The mechanical energy is converted by the hair cells of the
cochlea into electrical impulses through the cochlear nerve
to the brain. In order for the hair to convert the mechanical
energy the cell must contain pigment. Lack of pigment in
the inner ear is difficult to predict…but too much white in
Certain dogs seems to be correlated to the amount of white
found in the hair cells.
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Functions of the Eye
• The ocular system is responsible for vision.
• The combining forms for the eye or sight
are opt/i, opt/o, optic/o, ocul/o, and
ophthalm/o.
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Structures of the Eye
• The accessory structures of the eye:
– Orbit
• Bony cavity of the skull that contains the eyeball
– eye muscles
• 7 major muscles attach to each eye for movement
– eyelids or palpebrae
• Palpebral reflex (result of Trigeminal Nerve and CN VII)
– Also depth of anesthesia
– https://www.youtube.com/watch?v=4_zdjL51qoU
• Belphar/o is the combining form.
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Structures of the Eye
– eyelashes
• Hairlike structures called cilia
• Protect the eye from foreign material
– conjunctiva
• Mucous membrane that lines the underside of the eyelid
• Forms protective covering when the eyelids are closed
• Nictitating membrane=third eyelid.
– lacrimal apparatus
• Lacrim/o and dacry/o are the combining forms.
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Structures of the Eye
– lacrimal apparatus
• Lacrim/o and dacry/o are the combining forms.
• Lacrimal glands produce and secrete tears
• Lacrimal canaliculi or lacrimal duct collects tears and drains
them into the lacrimal sac
• Lacrimal sac collects tears at the upper portion of the tear duct
• Nasolacrimal duct is the passageway that drains tears into the
nose.
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Structures of the Eye
• Outer covering of the eyeball:
– Sclera
• White of the eye
• Fibrous outer layer that maintains shape of the eye
• Surrounds most of the eyeball
– Cornea
• The transparent anterior portion
of the sclera is called the cornea.
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Sclera and Cornea
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– Middle
Structures of the Eye
• Iris
– Colored portion of the eye
– Pigmented muscular diaphragm controls amount of light
– Located right behind the cornea
• Pupil
– Hole in the center of the iris through which light passes
» Constricts or dilates
• Lens
– Layers of connective tissue fibers
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• Choroid
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Main portion of the middle layer
Blood vessels
Dark pigmentation (caudal portion of the eye)
Tapetum Lucidum
» Very reflective “mother of pearl” blues and greens
» Aids night vision due to reflective nature
» Pigs and humans do not have a tapetum lucidum
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Structures of the Eye
– Inner layer
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Retina
Nervous tissue layer that receives images
Converts light rays into nerve impulses
Photoreceptors “rods and cones”
– Rods – light
– Cones - color and detail
• Send messages via the optic nerve
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Structures of the Eye
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Eye Chambers
• The eye is divided into parts:
– Anterior segment contains watery fluid called aqueous humor.
• anterior chamber
• posterior chamber
– Vitreous chamber contains vitreous humor.
• Gel like mass
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Patological Conditions
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Lenticular sclerosis
Cataracts
Glaucoma
Eye Enucleation
Eye Entropion
Tear Production
Scratches on the Cornea
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Lenticular Sclerosis
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Age associated
Hardening of the lens
Pupil appears cloudy and gray
Very little loss of vision
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Cataracts
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Protein and cellular debris clump together
Old age – gradual
Sudden – diabetes
White
Surgical removal of lens
• https://www.youtube.com/watch?v=4JFmPU50kZY
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Glaucoma
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Intraocular pressure
Very painful
Irreversible blindness
Different reasons
One reason is breed
predisposition
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• Intracular pressure should be between
12 and 25 mm Hg
• Can be measured with a tonometer or
tonopen
• Usually surgically remove the eye
– eye enucleation
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Eye Entropion
• An inversion (turned inward) of the eyelid
• Causes irritation of the cornea and sclera
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Tear Production
• “Dry Eye”
Lack of tears allows the normally
transparent cornea to become
thickened and opaque, leading to
blindness.
Corneal ulcers and bacterial
conjunctivitis are other disorders
occurring as a result of dry eye.
• Schirmer Tear Test
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Corneal Scratches / Ulceration
• If superficial “scratch”
– 1st layer
– epithelium
• Deeper ulceration
– 2nd / 3rd layers
– the liquid inside the eyeball
leaks out, the eye collapses
and irreparable damage
occurs.
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• Flourescein Stain adheres to ulceration
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Medical Terms for the
Ocular System
• Additional terms for ocular system tests,
pathology, and procedures can be found in
the text.
• Review StudyWARE to make sure you
understand these terms.
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