The Integumentary System
Chapter 6
Pp 112-124
Objectives
6.1 Skin and Its Tissues
Describe the structure functions of layers of the skin
Summarize factors that determine skin color
6.2 Accessory Organs
Describe the accessory organs associated with skin
6.3 Regulation of Body Temperature
Explain how skin helps regulate body temperature
6.4 Healing of Wounds
Describe the events that are part of wound healing
6.1 Skin and its Tissues
Cutaneous membrane ( the largest organ of the
body)
Surface area of 1.2 –2.2 square meters
Weighs 9-11 pounds (7% of total body weight)
Composed of two distinct regions
• Epidermis: superficial layer
• Dermis: deeper, thicker layer
• Beneath the dermis are masses of loose connective tissue and
adipose tissue that collectively form the subcutaneous layer
or the hypodermis.
6.1 Skin and its Tissues
Functions:
First line of defense against outside invaders
Prevents heat and water loss to maintain
homeostasis
Houses sensory receptors
Excretes waste
Produces biochemicals (oil and sweat)
Beauty is skin deep; ironic.
Composed of keratinized stratified
squamous epithelium cells
Outer layer of cells are older cells that have
hardened and filled with keratin (a protein)
We lose about 35,000 skin cells every minute
What happens to those lost cells?
The Epidermis
Replaced every 27 days
Some areas of the skin have five layers (soles and
palms) and some have only four.
Stratum Germinativum (Basale): deepest layer; attached
to dermis; youngest skin cells; reproductive layer
Stratum Spinosum:Several layers thick; contains
melanin (pigment that provides skin color)
Stratum Granulosum: thin, waterproofing layer
Stratum Lucidum: clear layer; present in the
soles of feet and palms of hands
StratumCorneum: outermost layer; cell
fragments; contains keratin to protect
skin;glycolipids waterproof this layer
Nutrients for the epidermis come from the
underlying dermis.
Skin Color
Biological Factors
Melanin: dark pigment that absorbs UV rays,
preventing mutations in the DNA of skin cells;
produces yellow to reddish to black coloring
• Melanin is produced by melanocytes.
• All people have the same amount of melanocytes.
It’s the amount of melanin they produce, that
determines color.
Environmental and Physiological Factors of
skin color
Sunlight, UV light from tanning beds, or Xrays increase production of melanin.
The amount of oxygen in blood affects the
color of hemoglobin. Excess oxygen leads to
pink tone; low amounts lead to cyanosis (bluish
tint)
Beta-carotene: yellow to orange tone due to
diets high in yellow veggies.
The Dermis: the hide
Strong, flexible connective tissue
Rich in nerve fibers, blood vessels, and
lymphatic vessels; hair follicles, oil and
sweat glands
Blood vessels here help regulate body
temperature
Stretch marks: stretching of the skin leading
to tearing of the dermis
Two dermal layers
Papillary layer
Vascular
Touch receptors called
Meissner’s corpuscles
Dermal ridges help
increase friction and
help create fingerprints
Reticular layer
80% of dermal
thickness
Fact or Myth?
Hair and fingernails of deceased
continue to grow.
A patch of skin approximately 2cm square and 1.5
mm thick has:
2.75 meters of blood vessels
300 eccrine glands
30 hairs
600 pain receptors
4 sebaceous glands
9000 nerve endings
6 cold sensors, 36 heat sensors, 75 pressure sensors
And almost 12 meters of nerves!
6.2 Accessory Organs
Nails
Protective covers on the
ends of fingers and toes
Specialized keratinized
cells
Hair Follicles
Hair develops from
epidermal cells originating
at the base of a follicle
Newly formed cells push
older cells outward to be
keratinized
Hair color is determined by
genes that control amount
of melanin produced
Grows an average of 9
inches/yr
Sebacceous glands
Usually associated with hair
follicles
Secrete sebum, a
waterproofing oil
Sweat Glands
A coiled tube
Sweat is primarily water but
also contains waste and salt
• Two types: apocrine and
eccrine
Try this at home!
Clean one palm of your hand with a cotton ball
soaked in rubbing alcohol. Use the other palm
as your control. Run water over both your
palms, shake off access water, and observe.
You will probably notice that the water soaks
in more on the palm that you cleaned with
alcohol. What is the purpose of the rubbing
alcohol in the experiment?
Sudoriferous Glands (Sweat glands):
Apocrine gland: become active at puberty;
respond to emotions and are located in the
axillary and groin regions
Eccrine gland: respond throughout life in
response to temperature; associated with
forehead, neck, and back
6.3 Regulation of Body
Temperature
The skin plays a key role in the homeostatic
mechanism that regulates body temperature.
Normal body temperature is 98.6F.
Body temp. increases:
• dermal blood vessels relax and swell,
• sweat glands produce sweat
Body temp. decreases:
• Dermal blood vessels contract pushing blood toward vital
organs
• Muscles in skin contract to produce friction
6.4 Healing of wounds
Inflammation
Redness, heat, swelling,
pain
Scabs are formed when
injury extends into the
dermis and escaping blood
forms a clot.
Granulations are small,
rounded masses in
exposed tissues of large
wounds. These lead to
scar formation.
Venous breakdown
Pressure Sore
Burns
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