Chapter 5
Integumentary System
5-1
• The skin is one of the largest and
heaviest organ of the body.
• In an average adult,
– the skin covers about 2 square
meters (22 square feet)
– weights 4.5-5 kg (10-11 lb) and
– varies in thickness (1.5 to 4.0 mm)
depending on what part of the body
it covers.
5-2
• The skin covers all of the
exposed surface of the body and
is continuous with the mucous
membranes lining openings into
the body surface, such as those
of the digestive, respiratory and
urogenital systems.
5-3
• The skin and its appendages(hair, nails,
sebaceous and sweat glands) make up a very
complex set of organs that accomplishes
several functions:
– Protection: barrier against the outside
– Protection against dehydration
– Body Temperature Regulation
– Cutaneous Sensation
– Metabolic Functions
– Blood Reservoir
– Excretion
5-4
• The skin consists of 2 layers,
• 1 - the outer epidermis, derived
from the embryonic ectoderm
and
• 2 - the inner dermis which
develops from the mesoderm.
5-5
• The appendages of the skin such as
hair, nails, sebaceous glands and sweat
glands develop from the embryonic
epidermis.
• Beneath the dermis is the hypodermis
(=subcutaneous tissue = superficial
fascia) which anchors the skin loosely to
underlying tissues (mainly muscles).
The hypodermis is NOT part of the
skin
5-6
THE EPIDERMIS
• The epidermis is a keratinized
stratified squamous epithelium
consisting of four distinct cell
types and five distinct layers.
• Its thickness varies: 0.07-0.12 mm
over most of the body to 0.8 mm
on the palms and 1.4 mm on the
soles.
5-7
THE EPIDERMIS
• Its surface layer, consists of dead cells,
rich in keratin, a protein which renders
it dry and more or less waterproof,
allowing it to resist surface evaporation
and preventing excessive water loss.
• It also serves as a protective barrier
against ultra-violet light, bacteria, many
chemicals and abrasion.
5-8
The epidermal cells are:
• 1 - keratinocytes
• 2 - Merkel cells
• 3 - melanocytes
• 4 - Langerhans cells
5-9
1 - the keratinocytes:
• compose most of the epidermis.
They produce a protein: the keratin
that helps waterproof the skin and
that protects the skin and the
underlying tissues from heat,
microbes, abrasion and chemicals.
5-10
2 - the Merkel cells:
• sensory receptors (touch).
They associate with a disclike sensory nerve ending to
form the Merkel disc.
5-11
3 - the melanocytes
• synthesize the melanin
pigments which protect the
skin against ultraviolet
damage.
5-12
4 - the Langerhans cells
• macrophages used in the
defense against
microorganisms.
5-13
The epidermis consists of several
layers of cells. From the deepest
to the most superficial:
• 1 - the stratum basale (or stratum
germinativum)
• 2 - the stratum spinosum
• 3 - the stratum granulosum
• 4 - the stratum lucidum
• 5 - the stratum corneum
5-14
1 - the stratum basale (or
stratum germinativum):
• is the deepest epidermal layer. It
consists of one row of cuboidal to
columnar shaped cells. Those cells
are mostly stem cells that divide
rapidly to produce new keratinocytes
which push up toward the surface
and become part of the more
superficial layers
5-15
• Ten to 25% of cells found
here are melanocytes: their
long branching processes
extend in between epidermal
cells and reach into the more
superficial Stratum spinosum.
Melanocytes synthesize the
pigment melanin.
5-16
• Melanin passes on from the
melanocytes into the
keratinocytes and will protect
them from the destructive
effect of ultraviolet radiation.
 Merkel cells are also found
in this layer.
5-17
2 - the stratum spinosum
• is 8-10 layers thick.
• The keratinocytes contain
thick bundles of
intermediate filaments
(tonofilaments) made of a
tension-resisting protein.
5-18
• Scattered amongst
keratinocytes are the
Langerhans'cells that are
most abundant in this layer.
5-19
• Stratum germinativum and
stratum spinosum
• are immediately adjacent to
the dermis and contain the
only epidermal cells that
receive adequate nourishment
(by diffusion of nutrients from
the dermis).
5-20
• As the daughter cells are
pushed upward, away from
the source of nutrition, they
gradually die and their soft
protoplasm becomes
keratinized (hard).
5-21
3 - the stratum granulosum
• here the keratinization process
begins and the cells begin to
die.
• This layer is called
granulosum because the cells
contain granules of the
precursor of keratine.
5-22
4 - the stratum lucidum
• is only found in thickened areas
of the epidermis such as the sole
of the feet.
• The cells appear clear (luci
means clear) because of an
accumulation of keratin
precursor. The cells begin to
degenerate.
5-23
5 - the stratum corneum
• is the outermost layer composed
of dead, flat, keratinized cells
which are being sloughed off
(they are your dandruff and the
flakes that slough off dry skin.
Corneum means horn: hard dead
cells
5-24
• An easy trick to remember these 5
epidermal layers in order from the most
superficial to the deepest:
"Can Little Girls Speak German"
• Can
Corneum
• Little
Lucidum
• GiRl
GRanulosum
• Speak
SPinosum
• GERMan GERMinativum
5-25
THE DERMIS
• The average thickness of the dermis is about
1 to 2 mm and varies from 0.6 mm on the
eyelids to 3 mm or more on the soles and
palms. It contains lots of nerve fibers,
sensory receptors, blood and lymphatic
vessels as well as the hair follicles, and the
sebaceous and sweat glands.
• The dermis consists of two layers:
5-26
1 - the Papillary layer
• is the outer layer closest to the
epidermis. It is composed of
areolar loose connective tissue. Its
superior region contains fingerlike
projections called dermal papillae
(also give the layer its name:
papillary) that indent the epidermis.
5-27
• Dermal papillae contain
capillaries, nerve endings
(pain receptors), Meisner
corpuscles (touch receptors:
make us feel light touching)
and the disc-like sensory
nerve endings of the Merkel
disks.
5-28
2 - the Reticular layer
• is the deeper layer and the thickest
(4/5th of the dermis). It is made of
dense irregular connective tissue
containing thick bundles of interlacing
collagen fibers and some coarse
elastic fibers that run in several
directions (but mostly in directions
that are parallel to the skin surface).
5-29
• The collagen fibers in the
reticular region provides the
skin with strength and
extensibility (= ability to
stretch) and
• The elastic fibers provide its
elasticity (= ability to return
to the original shape after
stretching).
5-30
• The reticular layer is richly
supplied with blood vessels
and nerves, and contains
sensory endings for touch
(Pacinian corpuscle for
sensing deep pressure such as
bumps), pain, heat, cold, etc.
5-31
• The epidermis projects down
into the dermis to form sweat
glands, sebaceous glands and
hair follicles.
5-32
THE SKIN APPENDAGES
• Organs such as hair, sweat glands
and sebaceous glands that develop
from the embryonic epidermis are
labeled appendages of the skin or
epidermal derivatives. Nail and the
enamel of your teeth also derive
from the epidermis.
5-33
HAIR
• The primary function of hair is protection:
in human, hair protect the scalp from
injury, from the sun ray and decrease heat
loss. Eyebrows and eyelashes protect the
eye from foreign particles. Hair in the
nostrils filter the air we inhale and hairs in
the external ear canal also prevent foreign
particles to penetrate there.
• Hair are made of dead keratinized cells.
5-34
The two regions of a hair are:
• 1 - the shaft
• 2 - the root
5-35
1 - the shaft
• It is the portion of the hair that projects
from the surface of the skin.
• The shape of the shaft determines the
curliness of your hair:
• round shaft -> straight hair
• oval shaft -> wavy/curly hair
• flat shaft -> kinky hair
5-36
2 - the root
• It is the portion of the hair
embedded in the skin. It
extends from the epidermal
surface into the dermis but
in the scalp, it can extend
into the hypodermis
5-37
• The hair (shaft and root) is
made of three tubes that fit
into each other.
• The three tubes are made of
keratinized cells.
5-38
The outer tube is the cuticle:
• it is made of one layer of
heavily keratinized cell.
5-39
The middle tube is the cortex:
• It contains several layers of
cells.
• The cells contain pigments in
dark hair and air bubbles in
white hair.
5-40
The inner tube is the medulla:
• it is composed of 2 or 3 rows
of cells containing pigments
and air spaces.
5-41
• The root of the hair is
contained inside a bag called
the follicle (follicle means bag).
• The base of this bag expends
forming the hair bulb.
5-42
• An extension of dermal
tissue called the papilla
protrudes inside the hair bulb
and contains capillaries that
supply nutrients to the
growing hair. Sensory nerve
endings called the root hair
plexus surround the bulb.
5-43
• The wall of this bag is made
of two layers:
–the external layer is the
connective tissue root sheath
derived from the dermis and
–The internal layer is the
epithelial root sheath derived
from the epidermis.
5-44
• Associated with each hair
follicle is a tiny band of smooth
muscle: the arrector pili. This
band of smooth muscle is
attached at one end to the
papillary layer of the dermis
and at the other to the
connective tissue root sheath of
the follicle.
5-45
• Contraction of the arrector pili in
hairy mammals raises the hair, thus
increasing the thickness of its coat.
This provide increased protection
against heat loss in cold weather or
increase in body size to intimidate
potential adversaries. In human,
contraction of these muscles causes
only "goose pimples".
5-46
SEBACEOUS GLANDS
• or oil glands are simple branched
areolar glands.
• They secrete the sebum (seb = oil) an
oily product.
• Sebum is usually secreted into a hair
follicle but in a few regions of the body
(lips and mammary papilla for
example) they are directly secreted
onto the skin surface.
5-47
• Sebum is a natural skin cream:
it helps hair from becoming
brittle, prevents excessive
evaporation of water from the
skin, keeps the skin soft and
contains a bactericidal agent
that inhibits the growth of
certain bacteria
5-48
• Sebaceous glands are scattered
all over the surface of the skin
except in the palms, soles and
the side of the feet.
5-49
SWEAT GLANDS
• or sudoriferous glands are
simple coiled tubular glands.
They are divided into two
principal types: eccrine and
apocrine.
5-50
• Eccrine glands are the most
common. Their secretory portion
can be located in the dermis or in
the hypodermis. They produce
sweat, a watery mixture of salts,
antibodies and metabolic wastes.
Sweat prevents overheating of the
body and thus helps regulate body
temperature.
5-51
• Apocrine glands are found mainly
in the skin of the armpits, and of
the areola of the breasts.
• Their secretory portion can be
located in the dermis or in the
hypodermis.
• Their excretory ducts open into
hair follicles.
5-52
• Their secretion is more viscous
than that of the eccrine glands.
They start secreting at puberty
and may be analogous to the
sexual scent glands of other
animals.
5-53
NAILS
• Nails are hard plates of tightly
packed keratinized cells. They are
clear and cover the dorsal surface
of the last phalanges of fingers and
toes. Nails protect the the ends of
the fingers, allow us to scratch
various parts of our body and help
us grasping and manipulating small
objects.
5-54
Each nail is made of three
regions:
• 1- the nail body:
• 2- the free edge
• 3- the nail root
5-55
1- the nail body:
• portion of the nail that is visible. The
nail body rests onto the nail bed: an
epithelium made only of the stratum
basal and the stratum spinosum.
There are no stratum granulosum,
stratum lucidum and stratum
corneum in the nail bed.
5-56
2- the free edge
• visible portion of the nail that
extend past the end of the digit.
It is the distal part of the nail
that you clip every now and
then.
5-57
3- the nail root:
• hidden portion of the nail that is
embedded in a fold of skin (or
nail fold). The cuticle is the
stratum corneum of the nail fold
that is pushed forward over the
nail.
5-58
• The site of nail growth is the
nail matrix that is found
beneath the nail root. The nail
matrix is thick and is only
composed of the deeper layer of
the epidermis: the stratum basal
(or germinativum).
5-59
• The keratinization of the cells
of the nail matrix proceeds in
the absence of a stratum
granulosum and lucidum and
this results into formation of a
of a rigid and durable plate.
5-60
• As the nail matrix thus
proliferates and differentiates,
this hard plate is pushed
forward onto the nail bed and
the nail grows. Look at your
nail, you will see a white
crescent called the lunula that
reflects the presence of the thick
matrix underneath
5-61
THE HYPODERMIS
• The Hypodermis (=
subcutaneous tissue =
superficial fascia) is NOT part
of the skin.
• It consists mainly of adipose
tissue plus some areolar tissue
5-62
• "Beer belly" in man and thick
thights and buttocks in female
are due to too much fat stored in
the hypodermis of these regions
of the body.
5-63
• Hypodermis shares the skin
protective functions: it stores
fat and thus helps prevent heat
loss and acts as a shock
absorber; it anchors the skin to
the underlying structures
allowing the skin to slide
almost freely over them.
5-64
Integumentary System
• Consists of:
–
–
–
–
Skin
Hair
Nails
Glands
• Functions
–
–
–
–
–
Protection
Sensation
Temperature regulation
Vitamin D production
Excretion
5-65
Hypodermis
• Skin rests on this,
but not a part
• Consists of loose
connective tissue
• Types of cells
– Fibroblasts
– Adipose cells
– Macrophages
• Also called
– Subcutaneous tissue
– Superficial fascia
5-66
Skin
• Dermis
– Structural strength
– Cleavage lines
– Two layers
• Reticular
• Papillary
• Epidermis
– Avascular
– Cells
– Layers or strata
5-67
Cleavage or Tension Lines
• Elastin and collagen
fibers oriented in
some directions
more than others
• Important in
surgery
– If incision parallel
to lines there is less
gapping, faster
healing, less scar
tissue
5-68
Dermis and Epidermis
5-69
Epidermal Cells
• Cell types
–
–
–
–
Keratinocytes: Produce keratin for strength
Melanocytes: Contribute to skin color
Langerhans’ cells: Part of the immune system
Merkel’s cells: Detect light touch and pressure
• Desquamate: Older cells slough off
• Keratinization: Cells die and produce outer
layer that resists abrasion and forms
permeability layer
5-70
Epidermal Strata
• Stratum Basale
– Deepest portion of epidermis and single layer
– High mitotic activity and cells become keratinized
• Stratum Spinosum
– Limited cell division
• Stratum Granulosum
– In superficial layers nucleus and other organelles
degenerate and cell dies
• Stratum Lucidum
– Thin, clear zone
• Stratum Corneum
– Most superficial and consists of cornified cells
5-71
Epidermal Layers and Keratinization
5-72
Thick and Thin Skin
• Thick skin
– Has all 5 epithelial strata
– Found in areas subject to pressure or friction
• Palms of hands, fingertips, soles of feet
• Thin skin
– More flexible than thick skin
– Covers rest of body
5-73
Skin Color
• Determined by 3 factors
– Pigments
• Melanin: Provides for protection against UV light
• Albinism: Deficiency or absence of pigment
• Carotene: Yellow pigment
– Blood circulating through the skin
• Imparts reddish hue and increases during blushing,
anger, inflammation
• Cyanosis: Blue color caused by decrease in blood
oxygen content
– Thickness of stratum corneum
5-74
Accessory Skin Structures
• Hair
– Found everywhere on human body except palms, soles,
lips, nipples, parts of external genitalia, and distal
segments of fingers and toes
• Glands
–
–
–
–
Sebaceous or oil glands
Sudoriferous or sweat glands
Ceruminous glands
Mammary glands
• Nails
5-75
Hair Structure
• Composed of shaft
and root
– Shaft protrudes
above skin surface
– Root located below
surface and base
forms the hair bulb
• Has 3 concentric
layers
– Medulla: Central axis
– Cortex: Forms bulk
of hair
– Cuticle: Forms hair
surface
5-76
Hair Growth, Color, and Muscles
• Hair Growth
– Cycles
• Growth and resting
– Permanent hair loss
• Pattern balding most common
• Hair Color
– Caused by varying amounts and types of melanin
• Muscles
– Arrector pili: Muscle contraction causes hair to “stand
on end”
5-77
Oil and Sweat Glands
• Sebaceous glands
– Produce sebum
– Oils hair and skin
surface
• Sudoriferous glands
– Merocrine or eccrine
• Most common
• Numerous in palms and
soles
– Apocrine
• Found in axillae,
genitalia, around anus
5-78
Nails
• Anatomy
– Nail root proximally
– Nail body distally:
Eponychium or
cuticle
• Growth
– Grow continuously
unlike hair
5-79
Burns
• Classifications
– First-degree
– Second-degree
– Third-degree
• Skin Grafts
– Split skin
– Artificial skin
– Cadavers or pigs
5-80
The Rule of Nines
5-81
Aging Effects
• Skin more easily damaged
• Skin becomes drier
• Functioning melanocytes decrease or
increase as with age spots
• Sunlight ages skin more rapidly
5-82
Clinical Disorders
• Bacterial infections
– Acne
• Viral Infections
– Chicken pox, German measles, cold sores
• Decubitus ulcers or bedsores
– Ischemia and necrosis
• Cancer
– Basal cell carcinoma
– Squamous cell carcinoma
– Malignant melanoma
5-83