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The Integumentary System
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Do Now
1. Why is skin considered an organ?
2. What are the major functions of
skin
3. Name 4 types of cells present in
the skin
4. Name the 5 layers of Epidermis
Do Now
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Which is the outer layer of skin:
Epidermis, dermis or hypodermis?
Name the pigment present in skin.
What are freckles?
What are moles?
Structure of the Skin
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Also called the cutaneous
membrane or the integument
Covers the entire surface of the
body
Largest organ in the body (weighs
10-11 lbs, 15% of body weight)
Comprised of all 4 tissue types
The integumentary system is made
up of the skin and several accessory
organs
Structure of the Skin
o
Made up of 2 layers
•
Epidermis
Outer, thinner region
Made of stratified squamous epithelium
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Five layers (strata)
Stratum Basale (deep)
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum (superficial)
Dermis


Made of connective tissue layer
Rests on hypodermis or subcutaneous layer
(below skin)
Layers of Epidermis
Layers: Superficial to Deep
5
4
3
2
1
Structure of the Skin
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Stratum Basale
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Single layer of columnar cells sitting on basement
membrane
Just superficial to dermis
Constantly dividing and new cells are pushed to the surface
As cells move toward the surface of the epidermis, they die
Cells Types in this layer
Keratinocytes-undergo mitosis to replace epidermis
constantly
Langerhans cells – macrophages
Melanocytes – produce melanin
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Give Skin its color
Protect cell nucleus from UV radiation
Tactile cells (Merkel cells) – touch sensations
Sensory nerves
Free nerve endings – pain and temperature sensations
Structure of the Skin
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Stratum Spinosum
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Several layers thick, made of keratinocytes
appear spiny
Stratum Granulosum
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3 to 5 layers of flat keratinocytes
Help to waterproof the skin
forms a barrier between surface cells
and deeper layers of the epidermis
cuts off surface layers from nutrient
supply
Structure of the Skin
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Stratum Lucidum
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Just deep to stratum corneum
Found only in thick skin (palms, soles)
Provides protection from constant friction
Cells have no nucleus or organelles
Stratum Corneum
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Tough, uppermost layer of epidermis
Upto 30 layers of cells that are keratinized
(hardened)
Keratin prevents water loss and water gain
Serves as a mechanical barrier against
microbes
Structure of the Skin: Dermis
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Thicker than epidermis
Made of dense, irregular connective tissue
Dermal papillae: present in thick skin, form
fingerprints, act as adhesive between dermis
and epidermis, provide large surface area for
blood supply to epidermis
Collagenous fibers prevent skin from being torn
Elastic fibers stretch to allow movement of
muscles and joints
Vascularization of dermis supplies oxygen and
nutrients to cells of dermis and epidermis
Numerous sensory nerve fibers
Skin Color
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Determined by Genetics and other factors
Melanocytes present in deeper layers of epidermis
produce a pigment called melanin
Darker skin color is due to more melanin NOT more
melanocytes
Prolonged UV exposure increases melanin production to
protect against UV damage (tanning)
Excessive exposure mutates melanocytes, causing
melanoma
Yellow tone of Asian skin is due to a pigment called
carotene, pink tone is due to hemoglobin.
Skin Markings
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Hemangiomas (birthmarks)
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discolored skin caused by benign
tumors of blood capillaries
Freckles & Moles: Aggregations of
melanocytes
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freckles are flat; moles are elevated
Hypodermis
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Subcutaneous layer located below the
dermis
Composed of loose connective tissue, has
more fat than dermis
Functions
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Energy storage
Insulation
Hypodermic injections: into subcutaneous
tissue as it is highly vascular
Do Now
Skin is made up of 2 layers.
1.
2.
The outermost layer of the skin is ___
Five layers of ____ from deepest to most
superficial are: Stratum
a.
d.
basale
b. corneum c. lucidum
spinosum e. granulosum
3. Type of tissue that makes up the top layers
________
4. Type of tissue that makes up the second
layer________
5. List 5 functions of the skin
Accessory Structures of the Skin
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Hair
•
On all body parts except the palms, soles,
lips, nipples, and portions of the external
reproductive organs
After puberty there is noticeable hair in the
axillary and pelvic regions
Hirsutism – characterized by excessive body
and facial hair in women due to increased
production of male sex hormone
Alopecia – hair loss
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Androgenic alopecia – male pattern baldness
Alopecia areata – sudden onset of patchy hair loss
Hair
• Hair follicles
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Formed from epidermal cells
Located in dermis
Cells become keratinized as they are pushed
out
Hair root – portion of hair within follicle
Hair shaft – portion of hair that continues
beyond the skin
• Sebaceous (oil) glands
• Arrector pili muscle – smooth muscle
attached to hair follicle
Nails
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Nails
•
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Formed from
specialized epithelial
cells
Nail root – base of
the nail
Nail body – visible
portion of the nail
Cuticles – fold of skin
that hides the root
Epithelial cells
become keratinized
as they move away
from the root
Glands
o Glands –
specialized cells
that produce and
secrete
substances into
ducts
• Sweat glands
• Sebaceous glands
Glands
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Sweat (sudoriferous) glands – active
under stress
Apocrine glands
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Eccrine sweat glands
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Open into hair follicles in anal region, groin, and
armpits
Begin to secrete at puberty
Mammary glands are modified apocrine glands
Open onto surface of skin
Active when body heats up; helps lower body
temperature
Sweat (perspiration) is mostly water, but also
excretes wastes
Ceruminous glands – modified sweat
glands that produce cerumen (earwax)
Glands
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Sebaceous glands
Most are associated with a hair follicle
Secrete an oily substance called sebum
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Lubricates and waterproofs hair and skin
Weakens or kills bacteria on skin surface
If sebum collects, whiteheads or
blackheads form
Acne vulgaris – inflammation of the
sebaceous glands
Functions of the Skin
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Protection
Safeguards from physical trauma
Protection from UV radiation
Help prevent bacterial invasion
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Sebum is acidic, which retards growth of
bacteria
Langerhans cells phagocytize pathogens and
alert the immune system to the presence of
pathogens
Gather sensory information
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Sensory receptors in the epidermis
and dermis are specialized for touch,
pressure, pain, hot, and cold
Receptors supply the central nervous
system with information about the
external environment
Homeostasis: Helps regulate body
temperature
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If body temperature rises, blood vessels
in the skin dilate and sweat glands
become active
If the outer temperature is cool, blood
vessels constrict
Arrector pili muscles contract, but
insulating effect is absent in humans
Hyperthermia - body temperature above
normal
Hypothermia – body temperature below
normal
Homeostasis:
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Regulation of water loss
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Keratinized cells prevent water from
entering the body
Water is excreted through perspiration
Vitamin D production
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Small amounts of UV radiation are
needed
Vitamin D leaves the skin and enters the
liver and kidneys
Disorders of the Skin
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Athlete’s foot – fungal infection often
involving skin of the toes and soles
Impetigo – bacterial infection common
in young children
Psoriasis – chronic condition where skin
develops pink or reddish patches
Eczema – inflammation of the skin
Dandruff – caused by a dry scalp
producing flaking and itching
Urticaria (hives) – allergic reaction
causing reddish, elevated, and often
itchy patches
Skin Cancer
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Begins with mutation of the skin cell
DNA
Non-melanoma cancers – less likely
to metastasize
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Basal cell carcinoma
Squamous cell carcinoma
Melanoma cancers
Skin Cancer
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Basal cell carcinoma
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Most common type of skin
cancer
Ultraviolet (UV) radiation
causes epidermal basal
cells to form a tumor
Signs are varied
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Open sore that will not
heal
Recurring reddish patch
Smooth, circular growth
with a raised edge
Shiny bump
Pale mark
95% of patients are easily
cured by removal
Skin Cancer
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Squamous cell carcinoma
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Five times less common
than basal cell carcinoma
More likely to spread than
basal cell carcinoma
About 1% of cases result
in death
Triggered by excessive UV
exposure
Signs are the same as
those for basal cell
carcinoma, but may also
resemble a wart or scaly
growth that bleeds and
scabs
Skin Cancer
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Melanoma
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More likely to be malignant
Starts in the melanocytes
Has the appearance of an
unusual mole
Warning signs
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Asymmetry
Irregular borders
Uneven color
Diameter greater than
6mm
Most common in fairskinned persons
Wounds
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Wound Healing
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Causes an inflammatory response
Steps in wound healing
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A blood clot forms
White blood cells and fibroblasts move to
the injured area
Fibroblasts pull the margins of the wound
together and promote tissue regeneration
The basal layer of the epidermis produces
new cells
Proliferating fibroblasts form a scar
Disorders of the Skin
Burns
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Burns
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Usually caused by heat
Burn severity affected by:
Extent of the burned area
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“Rule of nines” is a technique used to estimate
the extent of a burn
Lund-Browder chart is used for children
Burns
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Depth of the burn
First degree burn
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Second degree burn
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Extends through entire epidermis and part of the
dermis
Redness, pain, and blistering
Third degree burn
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Only epidermis affected
Redness and pain
No blisters or swelling occurs
Destroys entire thickness of the skin
Surface of wound is leathery and may be brown, tan,
black, white, or red
Patient feels no pain
Fourth degree burn – involve tissues down to
the bone
Burns
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Burns are considered a critical injury if:
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Second-degree burns cover 25% or more of the
patient’s body
Third-degree burns cover 10% or more of the
patient’s body
Any portion of the body has a fourth-degree burn
Third-degree burns occur on the face, hands, or
feet
Major concerns associated with severe
burns:
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Fluid loss
Heat loss
Bacterial infection
Aging
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Rate of cell mitosis decreases
Dermis becomes thinner and the dermal
papillae flatten
Adipose tissue in the hypodermis decreases
Collagen decreases
Elastic fibers in upper layer of dermis are lost
and those in the lower layer become thicker,
less elastic, and disorganized
Wrinkles form because of:
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Loose epidermis
Fewer fibers
Less padding in hypodermis
Aging
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Limited homeostatic adjustment to
heat because of:
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Less vasculature (fewer blood
vessels)
Fewer sweat glands
Number of hair follicles decreases
Reduced number of sebaceous
glands
Number of melanocytes decrease