Transcript Nerve activates contraction

Integumentary System
 Skin (cutaneous membrane)
 Skin derivatives
 Sweat glands
 Oil glands
 Hairs
 Nails
Skin Functions
 Protects deeper tissues from:
 Mechanical damage
 Chemical damage
 Bacterial damage
 Thermal damage
 Ultraviolet radiation
Vitamin D Production
• Vitamin D is important in the
uptake of Calcium from the food
you eat.
– Ca has to be absorbed from
your stomach into the blood
to go anywhere
– Cholesterol molecules when
exposed to UV light become
a Vitamin D precurser
– Precurser becomes active in
the liver & kidneys
Sensation – skin receptors
• Free nerve ending = pain
• Meissner’s corpuscles = discriminating touch,
light pressure (think fly on your arm)
• Krause’s – cold
• Ruffini’s – heat
• Merkel Disc – Medium pressure
• Pacinian corpuscle – Deep pressure
Sensation – skin receptors
• Free nerve ending = pain
• Meissner’s corpuscles = discriminating touch,
light pressure (think fly on your arm)
• Krause’s – cold
• Ruffini’s – heat
• Merkel Disc – Medium pressure
• Pacinian corpuscle – Deep pressure
Skin Functions
 Aids in heat regulation
 Aids in excretion of urea and
uric acid
 Synthesizes vitamin D
Slide 4.9b
Skin Functions-Excretion
• Limited amounts of nitrogen containing
wastes (most is excreted in urine unless you
have a kidney disorder in which case urea will
be excreted in small amounts through skin)
• Sodium chloride through sweat
• Water through sweat
• Heat through sweat
Homeostasis of Body Temperature
• Heat production – chief determinant is muscle
activity
• Heat loss/gain
– 80% of heat transfer is through the skin – the rest
is through the mucosa (dogs are opposite!)
– Regulated by vasoconstriction & vasodilation since
heat is carried primarily in the water content of
the blood
Skin Allows Heat to Escape.
• Blood vessels in skin dilate, allowing heat to
escape near the upper surface of the dermis.
This helps to cool the body.
Skin Keeps the Blood Warm
• Blood vessels constrict in the skin, keeping
blood in the hypodermis where fat can
insulate the blood and keep it warm.
Skin Structure
 Epidermis – outer layer
 Stratified squamous epithelium
 Often keratinized (hardened by keratin)
 Dermis
 Dense connective tissue
Epidermis
Layers of the epidermis.
Skin Structure
 Under the dermis is the hypodermis
 Not part of the skin
 Anchors skin to underlying organs
 Composed mostly of adipose tissue
Melanin
 Pigment (melanin) produced by
melanocytes
 Color is yellow to brown to black
 Melanocytes are mostly in the stratum
basale
 Amount of melanin produced depends
upon genetics and exposure to sunlight
Dermis
 Two layers
Papillary layer
 Projections called dermal papillae
 Pain receptors
 Capillary loops
Reticular layer
 Blood vessels
 Glands
 Nerve receptors
Skin Structure
Normal Skin Color Determinants
 Melanin
 Yellow, brown or black pigments
produced in melanocytes found in
stratum basale – transferred to
keratinocytes
 Local accumulations form freckles &
pigmented moles
 Amount of melanin produced depends
upon genetic and exposure to sunlight
 Solar elastosis – clumping of elastin
fibers = leathery looking skin
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 4.14
Normal Skin Color Determinants
 Melanin
 Yellow, brown or black pigments
 Carotene
 Orange-yellow pigment from some
vegetables
 Hemoglobin
 Red coloring from blood cells in dermis
capillaries
 Oxygen content determines the extent of
red coloring
Appendages of the Skin
 Sebaceous glands
 Produce oil
 Lubricant for skin
 Kills bacteria
 Most with ducts that empty into
hair follicles
 Glands are activated at puberty
Appendages of the Skin
 Sweat glands
 Widely distributed in skin
 Two types
 Eccrine
 Open via duct to pore on skin
surface
 Apocrine
 Ducts empty into hair follicles
Sweat and Its Function
 Composition
 Mostly water
 Some metabolic waste
 Fatty acids and proteins
 Function
 Helps get rid of excess heat
 Excretes waste products
 Acidic nature inhibits bacteria growth
 Odor is from associated bacteria
Blood Flow
 Vasodilation causes increase in
flow
 Vasoconstriction causes decrease
in flow
Appendages of the Skin
 Hair
 Produced by
hair bulb
 Consists of
hard
keratinized
epithelial cells
 Melanocytes
provide
pigment for hair
color
Hair Anatomy
 Central medulla
 Cortex surrounds
medulla
 Cuticle on outside of
cortex
 Single layer of
overlapping cells
 Split ends –
cuticle flakes off
– fibers in cortex
fray out
Figure 4.7b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 4.19
Cycles
Arrector Pili Muscle
Associated Hair Structures
 Hair follicle
 Dermal and
epidermal sheath
surround hair root
 Arrector pilli
 Smooth muscle
 Sebaceous gland
 Sweat gland
Appendages of the Skin
 Nails
 Scale-like modifications of the
epidermis
 Heavily keratinized
 Stratum basale extends beneath
the nail bed
 Responsible for growth
 Lack of pigment makes them
colorless
Nail Structures
 Free edge
 Body
 Lunula-a
whitish
crescent shape
around the
base of the nail
plate
Skin Homeostatic Imbalances
 Burns
 Tissue damage and cell death
caused by heat, electricity, UV
radiation, or chemicals
 Associated dangers
 Dehydration
 Electrolyte imbalance
 Infection
Rules of Nines
 Way to determine the extent of
burns
 Body is divided into 11 areas for
quick estimation
 Each area represents about
9%
Severity of Burns
 First-degree burns
 Only epidermis is damaged
 Skin is red and swollen
 Second degree burns
 Epidermis and upper dermis are
damaged
 Skin is red with blisters
 Third-degree burns
 Destroys entire skin layer
 Burn is gray-white or black
Critical Burns
 Burns are considered critical
if:
 Over 25% of body has second
degree burns
 Over 10% of the body has third
degree burns
 There are third degree burns of
the face, hands, or feet
First Degree Burn
• A first-degree burn is usually a minor red burn on
the skin's top layer, i.e. a mild sunburn. The
burned skin may hurt and be slightly swollen, and
could cause a slight fever. First-degree burns
usually heal with self-treatment (with an
ointment or cream, check w/your doctor) in about
3 to 5 days. They do not usually cause blisters or
scars.
Second-Degree Burn
• A second-degree burn is an injury to the skin. It is
usually caused by heat, radiation, chemicals,
electricity, or friction. It is also called a partialthickness burn. This type of burn affects both the
outer and underlying layer of skin. It can cause pain,
swelling and blistering.
Third Degree Burn
• A third-degree burn, also called a full-thickness burn, injures
all the skin's layers, as well as the fatty tissue beneath them,
and extends into deeper tissues. It causes white, blackened or
charred skin that may be numb to the touch. These are
serious burns that can affect the skin's ability to grow back.
• Common causes of third-degree burns are steam, hot oil,
grease, chemicals, electrical currents, and hot liquids.
• Infection is a major concern with third-degree burns. These
burns always require care from a doctor. With small burns,
new skin sometimes grows in from unburned areas. Large
burns may require skin grafts and surgery.
Third Degree Burn