Download 36–3 The Integumentary System

36–3 The Integumentary
System
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36–3 The Integumentary System
The skin, hair, nails, and a variety of glands make up
the integumentary system.
The skin is the largest organ in the body.
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36–3 The Integumentary System
The integumentary system:
• serves as a barrier against infection
and injury.
• helps to regulate body temperature.
• removes waste products from the body.
• provides protection against ultraviolet
radiation from the sun.
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36–3 The Integumentary System
The Skin
The Skin
The skin is made up of two main layers—the
epidermis and the dermis.
Beneath the dermis is a layer of fat (hypodermis)
and loose connective tissue that insulates the
body.
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36–3 The Integumentary System
Structures of the Skin
Nerves
Sweat pore
The Skin
Blood
Hair
vessels
Sebaceous
gland
Hair follicle
Epidermis
Dermis
Muscle
Sweat
gland
Hypodermis
Fat
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36–3 The Integumentary System
The Skin
Epidermis
The outer layer of the skin is the epidermis.
The epidermis has two layers.
• The outer layer is made up of dead cells.
• The inner layer is made up of living cells.
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36–3 The Integumentary System
The Skin
Cells in the inner layer undergo rapid cell division,
producing new cells that push older cells to the
surface of the skin.
Older cells flatten and their organelles disintegrate.
Older cells also begin making keratin, a tough,
fibrous protein.
When these cells die, they form a waterproof
covering on the skin’s surface.
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36–3 The Integumentary System
The Skin
The epidermis also contains melanocytes, which are
cells that produce melanin, a dark brown pigment.
Melanin protects the skin from sun damage.
Differences in skin color result from different amounts
of melanin and where melanocytes are distributed.
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36–3 The Integumentary System
The Skin
Dermis
The inner layer of the skin is the dermis.
The dermis contains collagen fibers, blood vessels,
nerve endings, glands, sensory receptors, smooth
muscles, and hair follicles.
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36–3 The Integumentary System
The Skin
The dermis contains two major types of glands:
• sweat glands
• sebaceous, or oil, glands
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36–3 The Integumentary System
The Skin
If your body gets too hot, sweat glands produce
sweat.
When sweat evaporates, it cools the body.
Sweat also gets rid of wastes from the blood, along
with water.
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36–3 The Integumentary System
The Skin
Sebaceous glands produce an oily secretion called
sebum.
Sebum spreads out along the surface of the skin and
helps to keep the skin flexible and waterproof.
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36–3 The Integumentary System
Hair and Nails
Hair
Hair covers most body surfaces. Hair:
• protects the scalp from ultraviolet light from the
sun.
• provides insulation from the cold.
• prevents dirt and other particles from entering
the body.
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36–3 The Integumentary System
Hair and Nails
Hair is produced by hair follicles, which are tubelike
pockets of epidermal cells that extend into the
dermis.
An individual hair is a column of cells that have filled
with keratin and died.
The oily secretions of sebaceous glands help
maintain the condition of each individual hair.
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36–3 The Integumentary System
Hair and Nails
Nails
Nails grow from rapidly dividing cells in the nail
root.
The nail root is located near the tips of the fingers
and toes.
During cell division, cells fill with keratin and
produce a platelike nail that covers and protects
the fingertips and toes.
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