2. Learning GoalsLearning Goals
Copy at TOP of page 43
1) Describe the 3 layers of the skin
including the location and what structures
are found in each.
2) Explain the 5 functions of the skin
including how each relates to
homeostasis.
3. 1. Integumentary System1. Integumentary System
The Integumentary
system includes:
◦ Skin – largest organ of
the body
◦ Accessory Organs:
Hair
Nails
Serves to protect the
viscera (internal organs)
and regulate temperature
4. 11. Structure of the Skin11. Structure of the Skin
The skin is composed of 3 layers from
superficial to deep:
5. 1. Epidermis1. Epidermis
Outermost layer of skin
Stratum Corneum – hard outermost
layer of epidermis
◦ Produces a protein called keratin
◦ Keratinization causes hardening of dead
skin cells, making skin waterproof.
Stratum Basale – produces new cells
of epidermis
◦ Contains Langerhans cells (for immunity)
and melanocytes (make pigment to give
skin color)
6. 2. Dermis2. Dermis
Thick layer of connective tissue
containing:
◦ Dermal papillae – ridges that cause
fingerprints and provide gripping surface
◦ Collagen & elastic fibers – stretching &
movement
◦ Blood vessels
◦ Sensory Nerves
◦ Sebaceous Glands
◦ Hair Follicles
7. 3. Hypodermis3. Hypodermis (Subcutaneous Layer)(Subcutaneous Layer)
Deepest layer of skin
Composed of loose connective
tissue and adipose tissue (fat)
◦ Helps to store energy, insulate body,
and provides protective padding
8. IV. Five Functions of the SkinIV. Five Functions of the Skin
1. Protection
• Physical barrier to disease, dirt, and
UV radiation
• Bacteria and other invaders are
prevented entry by the top dead layer
of skin and the acidic, oily secretion
from sebaceous glands (sebum).
9. 2. Regulates Water Loss2. Regulates Water Loss
Keratinization of the dead skin outer
layer also prevents water from entering
or leaving the skin, even when immersed
in water.
Skin works with the urinary system to
sweat off some excess water.
10. 3. Produces Vitamin D3. Produces Vitamin D
Melanocytes produce melanin to protect
against harmful UV radiation from the
sun and also to produce Vitamin D
Vitamin D helps regulate the uptake of
calcium by the digestive system.
Calcium is needed for strong bones.
11. 4. Gathers Sensory Information4. Gathers Sensory Information
Sensory receptors are linked to the
nervous system
Receptors specialize in sensing
◦ Touch
◦ Pressure
◦ Pain
◦ Temperature (hot & cold)
Many receptors in hands
12.
13. 5. Regulates Body Temperature5. Regulates Body Temperature
When the body is too hot, the skin
will help to release heat to cool the
body temperature back to 98.6°:
◦ Sweat
◦ Dilation of dermal blood vessels
14. When the body is too cold, the skin
will help to raise body temperature
back to 98.6° by generating heat:
◦ Shivering (muscle contraction)
◦ Goosebumps (contraction of arector pili
muscles attached to hair follicles) cause
hair to trap heat
◦ Constriction of dermal blood vessels
15. Bad things happen when body temp.
is not constant:
◦ 1. Hypothermia -Lower body temp.
than normal interferes with the body’s
normal functions and eventually ends in
death
