Integumentary System
Functions
1. Covers and protects
the body
What does the skin
protect us from?
 Pathogens
 Injury
 Ultra-violet radiation
Functions
2. Regulate body
temperature
How does it regulate
temperature?
 Sweating
 Dilate/constrict of
blood vessels
 Goose bumps
Functions
3. Excretes Waste
What
wastes are
excreted?
Urea
as sweat
subcutaneou
Functions
4. Reduces water loss
Keeps the body from drying out!
Functions
5. Houses sensory receptors
Chemo
Mechano
Chemo
Photo
Mechano
Four basic types of integumentary
tissue
Epithelium – epidermis
Connective tissue - dermis
Muscle tissue
Nervous tissue
There are 2 main layers of skin
I. Epidermis
II. Dermis
Epidermis
 Keratinized stratified squamous epithelium
 Four types of cells




Keratinocytes – deepest, produce keratin (tough fibrous protein)
Melanocytes - make dark skin pigment melanin
Merkel cells – associated with sensory nerve endings
Langerhans cells – macrophage-like dendritic cells
 Layers (from deep to superficial)
 Stratum basale or germinativum – single row of cells attached to
dermis; youngest cells
 Stratum spinosum – spinyness is artifactual; tonofilaments
(bundles of protein) resist tension
 Stratum granulosum – layers of flattened keratinocytes
producing keratin (hair and nails made of it also)
 Stratum lucidum (only on palms and soles)
 Stratum corneum – horny layer (cells dead, many layers thick)
(see figure on next slide)
Epidermis
Stratum
corneum
Outer (surface) layers
of skin
Dead
keratinocytes
Stratum
lucidum
Stratum
granulosum
10-30 cells thick
Lamellar granules
Keratinocyte
Two Parts:
Inner part
composed of
cells
Outer part
of dead cells
Langerhans cell
Stratum
spinosum
living
Melanocyte
is
Stratum
basale
Dermis
Merkel cell
Tactile disc
Sensory neuron
Epidermis
Inner layers
Lowest layer of cells
reproduce and
push older cells
toward the
surface.
As cells near the
surface, they
flatten and their
organelle
disintegrate
Epidermis
Inner layers
These cells also
begin
producing
Keratin a
tough, fibrous
protein.
This replaces
cytoplasm.
Epidermis – Outer layers
The Keratin producing
cells die as they move
toward the surface.
Outer dead layer
waterproofs and
protects inner layers
It is shed continually and
is completely replaced
in 2 - 4 weeks
Epidermis
What do we find in the epidermis?
Melanocytes
What are melanocytes?
Cells that produce melanin.
What is melanin?
A dark brown pigment
What does melanin do?
Gives skin it’s color
Protects sensitive dermis from U-V radiation
Skin color
Three skin pigments
 Melanin: the most important
 Carotene: from carrots and yellow vegies
 Hemoglobin: the pink of light skin
Melanin in granules passes from
melanocytes (same number in all races)
to keratinocytes in stratum basale
 Digested by lysosomes
 Variations in color
 Protection from UV light vs vitamin D?
Epidermis
Melanocytes
Do some people have
more melanocytes
than other people?
Epidermis
Skin pigmentation is due
to the type and amount
of melanin produced
Eumelanin produces
darker pigments
Phaeomelanin produces
lighter pigments and
freckles
These often occur
together in varying
amounts
Dermis
Deeper layers of skin
10-20 times thicker
than epidermis.
Top layer arranged
In ridges.
Dermis
Ridges help the
epidermis bind to the
dermis.
The uneven ridges
create fingerprints
Accessory Organs of the Dermis
1. Hair follicles – tube-like depression
where the hair develops
Hair and hair follicles: complex
Derived from epidermis and dermis
Everywhere but palms, soles, nipples, parts of genitalia
*
*“arrector pili” is smooth muscle
Hair bulb:
epithelial cells
surrounding
papilla
Hair papilla
is connective
tissue______________
__
Functions of hair
 Warmth – less in man than other mammals
 Sense light touch of the skin
 Protection - scalp
Parts
 Root imbedded in skin
 Shaft projecting above skin surface
Make up of hair – hard keratin
Three concentric layers
 Medulla (core)
 Cortex (surrounds medulla)
 Cuticle (single layers, overlapping)
 Types of hair
 Vellus: fine, short hairs
 Intermediate hairs
 Terminal: longer, courser hair
 Hair growth: averages 2 mm/week
 Active: growing
 Resting phase then shed
 Hair loss
 Thinning – age related
 Male pattern baldness
 Hair color
 Amount of melanin for black or brown; distinct form
of melanin for red
 White: decreased melanin and air bubbles in the
medulla
 Genetically determined though influenced by
hormones and environment
Accessory Organs of the Dermis
2. Sebaceous glands – secret oily sebum
to soften and waterproof skin
Sebaceous (oil) glands
 Entire body except palms and soles
 Produce sebum by holocrine secretion
 Oils and lubricates
Accessory Organs of the Dermis
3. Nails – protective covers of ends of
fingers and toes.
Nails
Of hard keratin
Corresponds to hooves and claws
Grows from nail matrix
Accessory Organs of the Dermis
4. Sweat glands:
 secrete waste
 regulate heat
 produces ear wax
 produces milk during lactation
Sweat glands
 Entire skin surface except nipples and part of
external genitalia
 Prevent overheating
 500 cc to 12 l/day! (is mostly water)
 Humans most efficient (only mammals have)
 Produced in response to stress as well as heat
Types of sweat glands
 Eccrine or merocrine
 Most numerous
 True sweat: 99% water, some salts, traces of waste
 Open through pores
 Apocrine
 Axillary, anal and genital areas only
 Ducts open into hair follices
 The organic molecules in it decompose with time - odor
 Modified apocrine glands
 Ceruminous – secrete earwax
 Mammary – secrete milk
Types of sweat glands
 Eccrine or merocrine
 Most numerous
 True sweat: 99% water, some salts, traces of waste
 Open through pores
 Apocrine
 Axillary, anal and genital areas only
 Ducts open into hair follices
 The organic molecules in it decompose with time - odor
 Modified apocrine glands
 Ceruminous – secrete earwax
 Mammary – secrete milk
Accessory Organs of the Dermis
5. Blood vessels – to nourish skin cells
Accessory Organs of the Dermis
6. Nerves – to send and receive messages
Subcutaneous
Accessory Organs of the Dermis
7. Erector pilli muscle
-smooth muscle
-causes
“goosebumps”
-causes
hair to
stand erect
subcutaneous
Subcutaneous layer – connective
tissue
Anchors dermis to the body
Contains fat
cells to
protect
and cushion
Subcutaneous layer
Some disorders of the integumentary
system
Burns
 Threat to life
 Catastrophic loss of body fluids
 Dehydration and fatal circulatory shock
 Infection
 Types
 First degree – epidermis: redness (e.g. sunburn)
 Second degree – epidermis and upper dermis:
blister
 Third degree - full thickness
Infections
Skin cancer
Disorders of the integumentary system
Burns
 Threat to life
 Catastrophic loss of body fluids
 Dehydration and fatal circulatory shock
 Infection
 Types
 First degree – epidermis: redness (e.g. sunburn)
 Second degree – epidermis and upper dermis:
blister
 Third degree - full thickness
Infections
Skin cancer
Interesting Tidbits
 Your body is composed of approximately 100
Trillion cells
 About 16% of your body weight is skin
 The skin is completely renewed every 27 days
 You will make almost 1000 new skins in a
lifetime
 If all the layers of your skin were laid out on the
ground, it would cover about 20 m2 or 2
parking spaces
Interesting Tidbits
A fingernail or toenail takes about 6
months to grow from base to tip
Fingernails grow faster than toenails
An average human scalp has 100,000
hairs
We lose between 40 and 100 hairs per
day
Blondes have more hair than brunettes
Interesting Tidbits
 Fingerprints provide traction for grasping
objects
 Even identical twins have different fingerprints
 Every square inch of dermis contains twenty
feet of blood vessels
 Skin on our hands and feet is thicker. When
we bathe, skin takes on water and swells
slightly.
 In the thicker areas, increased surface area
creates crowding. The skin must wrinkle to
accommodate the changes
Interesting Tidbits
 Friction of the epidermis causes cell division to
increase.
 This outward thickening is called a callous.
 Sometimes growth is inward, creating a corn.
 Humans shed about 600,000 particles of skin
per hour – about 1.5 pounds per year.
 At age 70, you will have lost about 105 lbs of
skin.