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Major roles of the
Integumentary System
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protection
maintenance of normal
body temperature
storage (of fat)
synthesis (of vitamin D)
excretion (of salts, water
and wastes in sweat)
sensory perception
The Skin: 3 Major layers
Did You
Know?...
 At 8-10
pounds, the
skin is bodies
largest organ!
The Epidermis
 The epidermis is the outer
layer of skin. The
thickness of the epidermis
varies in different types of
skin. It is the thinnest on
the ______ at .05 mm and
the thickest on ______ at
1.5 mm.
 Cells of the epidermis are
constantly sloughing off
and replacing
themselves…
The Epidermis cont…
5 layers
 Cells are shaped like
columns at the base and
migrate upward, as dead
cells are continuously
sloughed off at the surface
•stratum corneum
•stratum lucidum
•stratum granulosum
•stratum spinosum
•stratum basale
Epidermal Layers
stratum corneum
the outermost layer of the epidermis
is composed of large, flat, plate-like
cells filled with keratin, these dead
cells have migrated up from the
stratum granulosum
stratum lucidum
This thin layer is made up of 3 to 5 layers
of dead, flattened keratinocytes. Here,
melanocytes determine the darkness of the
stratum lucidum. Thickness of the lucidum
is controlled by the rate of mitosis in the
cells below.
stratum granulosum
In this, the granular layer, cells have lost
their nuclei and are characterized by dark
clumps of cytoplasmic material. There
significant activity here, as keratin proteins
and water-proofing lipids are being
constructed/organized.
Epidermal Layers
stratum spinosum
Cells that move into the spinosum layer
(referred to as the prickle cell layer)
change from being columnar to
polygonal. In this layer the cells start to
synthesize keratin.
stratum basale
The bottom layer the epidermis responsible
for constantly renewing epidermal cells.
This layer contains a single row of
columnar stem cells that divide very
frequently. About Half of the cells begin to
flatten and move to the next layer in the
maturation process. The other half remain
in the basal layer and divide over and over.
Which layer of the epidermis is this?
Specialized Epidermal Cells
 The melanocyte- produces pigment (melanin)
 The Langerhans' cell- frontline defense of the immune
system in the skin
 Merkle Cells are highly sensitive ‘light’ touch receptors
(neurons) found in the basal layers of the epidermis
The Dermis
 This layer varies in
thickness as well,
depending on the area
of the body. It is a mere
0.3 mm on the eyelid
and 3.0 mm on your
back.
 The dermis is
composed of 3 types of
tissue….
The Dermis cont…
 2 types of tissue that
are present throughout
(not in layers).
 collagen
 elastic Areolar (loose)
connective tissue
Dermis: Elastic tissue
 Elastic protein fibers made by cells called fibroblasts
provide protection for tissues underneath the dermis as
well as the pliability we associate with the skin.
Areolar connective tissue
providing a support infrastructure for
blood vessels, nervous tissue and
specialized dermal structures. It also
acts as a reservoir for glucose,
essential ions, and water.
Dermis Tissue: Collagen
 Collagen is the most abundant and
important structural protein in your
body. It strengthens and supports
many body tissues from the outside
creating an “extracellular matrix.”
Specialized Dermal Cells
 arrector pili muscle cells support hair
follicles.
 oil (sebaceous) glands, scent glands, and
sweat glands are associated with the follicle.
 Blood vessels and nerves course through this
layer. The nerves transmit sensations of pain,
pressure, itch, and temperature, and blood
vessels facilitate gas exchange.
Glands Galore!
Sebaceous glands
 Sebaceous glands are located
near the hair follicle and produce
sebum - the natural oil of your
skin.
 Sebum is a mixture of different
waxes and fats, and the facial skin
contains nearly three thousand of
these glands per square inch.
Glands
(cont.)
Apocrine glands
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In the armpit, belly button, genital and anal areas
of the body
situated deep within the dermis and produce a
milky type of sweat, causing body odor when
bacteria breaks it down on the epidermis.
In animals these glands produce body odors that
attract sexual partners. Some believe the same
holds true for humans….
Eccrine glands
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Unlike sebaceous and apocrine glands, they do not
use the hair follicle to exit sweat to the skin, each has
its own dedicated pore.
Sweat glands regulate body temperature, as draws
heat away from the body.
Eccrine sweat is also helpful in eliminating waste salts
from the body.
1 Square inch if Skin
Contains…
What makes these hairs stand on end? Why?
Can you name
structures 1-4?
Layer 3: The Subcutaneous
 Also referred to as the
“hypodermis,” this layer of the
skin is composed primarily of
adipose tissue (fat). This layer
plays a key role in insulating the
body and regulating the
temperature of the skin.
 The hypodermis can vary
significantly in thickness and
incorporates larger blood vessels
and nerves.
Nails
 Your nails extend from the
epidermis and contain a
tough protein called
keratin. They play an
important role in grasping
objects, scratching, and
protecting fingers and
toes.
A. Nail plate; B. lunula; C. root; D.
sinus; E. matrix; F. nail bed; G.
hyponychium; H. free margin
Did you Know?
 Your fingernails grow about 5 times
faster than your toenails!
Hair
 Also composed of the
protein keratin hair
acts as an effective
insulator between you
and the environment.
 hair follicles originate
in the dermis.
Did you know?
 Humans have more hair than apes.
Although theirs is thicker, longer, and
typically darker.
Challenge Question!
 The hair in your ears, nose, and around
your eyes play important roles in keeping
you healthy….Can you explain why?
Did You Know?
 Hair can grow as
little as 0.1 inches
per month or as fast
as 0.5 inches per
month depending
on genetics and
your diet.
Damaging the Skin
Puncture wounds are caused by a sharp object that
penetrates the skin. Such wounds may cause
significant deep injury that is not immediately
recognized. These types of wounds do not bleed
freely
The most common type of open wound is a
laceration. Lacerations are commonly called
cuts and are an irregular cut or tear through
the skin.
Abrasions are commonly called scrapes. They
occur when the skin is rubbed across a rough
surface. Abrasions involve variable depths of skin.
An avulsion is a tearing away of body tissue.
Avulsions raise flaps of tissue, usually along
normal tissue planes. The avulsed part may
be totally severed from the body or it may be
attached by a flap of skin.
Aging and the
integumentary system
Marked declines in:
 Cell division in stratum basale
 Melanocyte production
 Glandular activity
 Hair follicle function
 Elastic fiber function in dermis
 Blood supply to skin
 Rate of repair
Disorders of the skin
•Lesions and tumors
•infections (bacterial, viral, fungal, parasitic)
•inflammatory reactions and allergies
•Genetic diseases
•acne
Anatomy of a Pimple