AMA 171 - Anatomy &
Physiology/Medical
Terminology/Pathology
2 Skin and Senses
Skin: (Integumentary System)
Interesting fact: weighs 8-10lbs and covers an
area of 22 square feet (in an average adult)
Functions:
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Covers and protects the internal organs and
tissues
Produces important secretions: oil and sweat
to lubricate and cool the body
Contains nerves that are receptors for
sensations such as pain, temperature,
pressure and touch
Thermoregulation of the body
Structure (layers of the skin):
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Epidermis: outermost layer made of squamous
epithelial cells; the basal layer of the epidermis is
always growing and multiplying
Dermis: middle layer composed of blood and lymph
vessels, nerve fibers and accessory organs, such as
hair follicles, sweat and sebaceous glands
Subcutaneous: deepest layer specializing in the
formation of fat; important in the protection of the
deeper tissues of the body, as a heat insulator and
for energy storage
Accessory organs: hair, nails &
glands
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Hair: fibers composed of keratin, a hard protein
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Nails: hard keratin plates covering the last bones of each toe
and finger
Glands:
 Sebaceous (oil): found almost everywhere, except hands and
feet. Lubricate the skin through the hair follicle and minimize
water loss from the body; influenced by sex hormones
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Sweat: most numerous on hands and feet but found on almost all
body surfaces. Almost pure water with dissolved materials such
as salt; odor comes from bacteria, not sweat. Sweat
(perspiration) cools the body as it evaporates into the air.
Sense Organs: Receptors that are
activated by stimuli from the
external or internal environment.
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Eye: light rays enter the eye and are
sent to the cerebral cortex of the
brain, fusing to form a visual sensation
with three-dimensional effect
Ear: sound waves are received by the
ear and sent to the auditory region of
the brain in the cerebral cortex
Structure of the eye
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Cornea: fibrous tissue covering pupil and iris, light enters here first, is bent or
refracted
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Anterior chamber: contains aqueous humor a fluid produced by the ciliary body
to nourish the eye and help maintain its shape
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Pupil: dark center of the eye, light rays enter here after passing through the
cornea
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Iris: colored portion of the eye, contains muscles that constrict pupil to regulate
light
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Conjuctiva: membrane that lines the eye and eyelids; clear and colorless unless
irritated
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Sclera: white of the eye, provides nourishment via blood vessels
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Choroid: dark brown membrane inside of sclera, contains blood vessels
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Lens: changes shape to refract light and to flatten or round the lens for
distance or close vision (accommodation)
Structure of the eye cont…
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Ciliary body: muscles that control the lens
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Vitreous humor: jelly-like fluid that helps maintain eye’s shape
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Retina: sensitive nerve layer of the eye, contains rods and cones
that are receptor cells responsible for color and central vision
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Optic nerve: chemical change from rods and cones cause nerve
impulses to send visual signal to brain through this nerve
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Optic disc: region where optic nerve meets the retina
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Macula: area that contains the fovea centralis
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Fovea centralis: depression in macula that is the location of the
sharpest vision in the eye
Structure of the ear: three regions
of
the
ear
Outer ear: conducts sound waves
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Pinna (auricle): flap of the ear
External auditory meatus (auditory canal): ear canal that
secretes ceruman (ear wax)
Middle ear: conducts sound waves
 Tympanic membrane (eardrum): sounds waves make this
vibrate
 Ossicles: three small bones that are vibrated by the sound
on the tympanic membrane: Maleus, Incus & Stapes
 Oval window: vibration from stapes touches this membrane
that separates the middle and inner ear
Inner ear (labyrinth): receives auditory waves and relays them
to the brain
 Cochlea: looks like a shell; contains liquids that transmit the
sound waves/vibrations
 Auditory nerve fibers: connect the cochlea to the brain so
the brain “hears” sounds