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The Body Covering (Fun Fact! Largest organ of the body)
Includes: Skin, Nails & Hairs
Skin A.K.A. Cutaneous Membrane
Functions:
– Body Temperature Regulation: Sweating at surface and
adjusting blood flow in dermis.
– Protection: Keratin protects from microbes, abrasions, heat
and chemicals, lipids slow evaporation of water, melanin
protects from UV rays.
– Cutaneous Sensations: Sensory input/output
– Excretion and Absorption: Eliminates substances, passage of
materials into body cells (drugs)
– Synthesis of Vitamin D: UV light activates creation of Vit D
• Skin is divided into
two main parts:
– Epidermis
(epi = above)
Surface epithelial
layer
– Dermis:
Deeper connective
tissue layer
• Subcutaneous Layer
Deep dermis not part
of the skin.
– Fibers from dermis
anchor skin to this
layer which then
allows for attachment
to other tissue and/or
organs.
• Made of keratinized stratified squamous epithelium
• Capable of regeneration (new cells ~ q4 weeks)
• 4 cell types:
– Keratinocytes: 90% of epidermal cells, 4 – 5 layers,
produces keratin (rough fibrous protein that protects
skin), waterproofs skin.
– Melanocytes: 8% of epidermal cells, produce the
pigment melanin, transfer melanin to keratinocytes,
susceptible to UV light damage.
– Langerhans cells: Produce immune response against
pathogens entering skin.
– Merkel cells: Detect touch/sensory sensations.
• Consists of two distinct regions:
– The superficial part is composed of
areolar connective tissue.
– The deeper part is composed of
dense irregular connective tissue.
• Attaches to the subcutaneous layer.
• The outer layer contains nerve
endings for touch, thermal
sensations, pain, tickling, and
itching.
• Skin color is due to the melanin in the epidermis,
carotene in the dermis, and hemoglobin in the
capillaries of the dermis.
– Melanin (Brown-Black pigment)
• Darkness depends on amount of melanin produced.
• Gives some protection against UV
– MALIGNANT MELANOMA, (cancer of the melanocytes), is a particularly
serious skin cancer. Liver or age spots, are non-cancerous clusters of
melanin.
– Carotene (Yellow-Orange pigment)
• In deeper skin and adipose layers
– Hemoglobin (Pink-Red pigment)
• Found in blood
• Depends on blood flow
1. What are the 5 functions of skin?
2. What are the two main parts of skin called?
3. What 4 cells make up the superficial/thinner part of
the skin?
4. What is the function of the subcutaneous layer?
5. What specific type of epithelial cells make up the
epidermis?
6. Which skin layer contains nerve endings?
7. Which pigments contribute to which skin color?
8. The shade of your skin depends on which factors?
9. What are the characteristics and functions of
keratinocytes?
1. What are the 5 functions of skin?
• Body Temperature Regulation
• Protection
• Cutaneous Sensations
• Excretion and Absorption
• Synthesis of Vitamin D
2. What are the two main parts of skin called?
• Epidermis and Dermis
3. What 4 cells make up the superficial/thinner part of the skin?
• Keratinocytes
• Melanocytes
• Langerhans cells
• Merkel cells
4. What is the function of the subcutaneous layer?
• Allows for skin to attach to other tissue and/or organs.
• Storage site for fat
• Supplies skin with blood (remember epithelial cells are avascular)
5. What specific type of epithelial cells make up the epidermis?
• Keratinized stratified squamous epithelium
6. Which skin layer contains nerve endings?
• Dermis
7. Which pigments contribute to which skin color?
• Melanin (black-brown), Carotene (yellow-orange), Hemoglobin (red)
8. The shade of your skin depends on which factors?
• Mainly depends on the amount of melanin produced by melanocytes, but it is the interaction of all in #7
that determines the shade of skin.
9. What are the characteristics and functions of keratinocytes?
• Makes up most of the epidermis
• Produces keratin (rough fibrous protein ) which protects skin
• Waterproofs skin
#10
• Function: Protection
– Injury
– UV light
– Foreign Particles
• Found: On most skin
surfaces
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Scalp
Brows
External genitalia
Not on palmar surfaces of
hand and fingers or
plantar surfaces of feet
Supatra is one of only 50 sufferers of Ambras
Syndrome documented since the Middle Ages. It
is caused by a faulty chromosome.
Yu was born in the city of Anshan in the Chinese
province of Anshan in 1979 and began growing hair
at the age of two that eventually covered
approximately 96% of his body.
• Composition:
– Keratinized cells
– Shaft: mostly above
ground
– Root: below surface
• Surrounded by hair
follicle
– Bulb: base of hair
follicle includes
matrix producing cells
and blood vessels.
– Nerves: hair root
plexuses
• Sensitive to touch
– Muscle (Smooth):
Arrector pili
• Contraction causes
goose bumps
Hair Shaft
Hair Root
Hair Root Plexus
Bulb
Arrector
pili
muscle
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Function: Secrete substances
Composition: Epithelial cells
Types:
Sebaceous Gland
– Sebaceous Glands: secrete oily sebum
• Protects skin from drying out and
Hair Root Plexus
bacteria
Bulb
• Connected to hair follicles
– Sudoriferous (soo-dor-IF-er-us) Glands:
secrete sweat
• Eccrine are widely distributed;
aid in thermoregulation
• Apocrine are found in the axilla,
groin, areolae, beard
– Ceruminous (se-ROO-mi-nus) Glands:
secrete wax
• External auditory canal
• Combine with sebum to produce
earwax
• Provide barrier against foreign bodies
• Function: Help us grasp,
manipulate objects, protect
ends of digits, scratching
• Composition: Plates of
packed keratinized cells of the
epidermis.
– Nail body: Visible portion
– Free edge: Part extending
past digit
– Root: Part not visible
• Growth: 1 mm per WEEK!
Slows within 2nd / 3rd decade
– Becomes brittle with age
Free Edge
Nail Body
Root
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4.
5.
6.
7.
What are the functions of hair?
What protein is hair composed of?
What 5 structures make up hair within skin?
What causes goose bumps?
What is sebum? Which gland secretes sebum?
Which gland aids in thermoregulation? How?
Which glad’s secretions combine with sebum to
produce earwax? Why is this important?
8. What are the functions of nails?
9. What specifically are nails made of?
10.Of the 5 nail parts, name the 3 you need to know?
1. What are the functions of hair?
• To protect from injury, UV light, and foreign particles
2. What protein is hair composed of?
• Keratin
3. What 5 structures make up hair within skin?
• Hair shaft
• Hair root
• Hair root plexus
• Blub
• Arrector pili muscle
4. What is sebum? Which gland secretes sebum?
• An oily substance produced by the sebaceous glands
5. What causes goose bumps?
• When the hair root plexus stimulates the arrector pili muscle it contracts causing the skin around
the hair shaft to elevate.
6. Which gland aids in thermoregulation? How?
• Eccrine sweat glands produce sweat; when the sweat evaporates it cools your skin.
7. Which gland’s secretions combine with sebum to produce earwax? Why is this important?
• Ceruminous glands’ secretions provide a sticky barrier against foreign bodies
8. What are the functions of nails?
• Grasp, manipulate objects, protection to the ends of fingers, scratching
9. What specifically are nails made of?
• Plates of tightly packed hard keratinized cells of the epidermis
10.Of the 5 nail parts, name the 3 you need to know?
1. Free Edge
2. Nail Body
3. Nail Root