The Special
Senses
Chapter 17
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Vision (sight)
Gustation (taste)
Olfaction (smell)
Hearing
Equilibrium
(balance)
Accessory Structures of the Eye
• Eyebrows divert
sweat and contribute
to facial expressions
• Eyelids (palpebrae)
blink to protect the
eye and lubricate their
surface
• Eyelashes detect and
deter foreign objects
Accessory Structures of the Eye Cont.
• Conjunctiva - a
mucous membrane
lining the inside of
the eyelids and the
anterior surface of
the eyes
• Conjunctivitis
(“pinkeye”) inflammation of
conjunctiva
Accessory Structures of the Eye Cont.
Lacrimal Apparatus:
– Lacrimal gland
– Lacrimal sac
– Nasolacrimal duct
• Keeps conjunctival
surfaces moist and
clean
Eye Muscles
• Lateral, medial, superior, and inferior rectus muscles;
superior and inferior oblique muscles
Internal Anatomy
of the Eye
• Aqueous humor - clear,
watery fluid in the anterior
chamber
• Cornea - transparent tissue
covering the front of the eye;
bends light
• Pupil - hole in the center
where light passes through
• Iris - controls the size of the
pupil; gives "color" to the eye
• Lens - transparent tissue that
bends light passing through
the eye
• Retina - on the back of the
eye, contains photoreceptors
(center of retina = fovea)
Internal Anatomy
of the Eye
• Rods - photoreceptors
responsive in low light
conditions
• Cones - photoreceptors
responsive to color and in
bright conditions
• Sclera – the “white” of the
eyeball
• Choroid – membrane
between sclera & retina
• Vitreous Humor - clear,
jelly-like fluid found in the
back portion of the eye,
maintains shape
www.uniteforsight
.org/course/eyea
natomy.php
http://www.youtu
be.com/watch?v=
gvozcv8pS3c
Visual Disorders
Myopia (nearsightedness) –
objects far away appear blurry;
can be corrected with concave
lenses (- diopter)
Hyperopia (farsightedness) –
close objects appear blurry; can
be corrected with convex
lenses (+ diopter)
Visual Disorders Cont.
• Astigmatism - uneven
curvature in cornea causes
out of focus image
• Cataract - clouding of the
lens, scatters the light rays
Visual Disorders Cont.
• Glaucoma - caused by a build-up of aqueous humor;
the excessive amount of fluid causes pressure against
the retina, affecting vision; if untreated, will result in
permanent blindness
• Presbyopia - form of hyperopia due to weakening of
eye muscles; normal part of aging