Integumentary System
Ms Clark
PVMHS
Integumentary System
• Made up of the skin and its accessory
structures
– Accessory structures:
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Hair
Nails
Glands
Sensory receptors
• The skin is the largest organ in the body
– It is an organ because it consists of different
tissues that are joined to perform specific
activities
• Dermatology is the branch of medicine that
specializes in diagnosing and treating skin
disorders
Functions of Skin
1.
2.
3.
4.
5.
6.
Regulation of body temperature
Protection
Sensation
Excretion
Immunity
Synthesis for Vitamin D
Functions of Skin
1. Regulation of body temperature
– Evaporation of sweat , changes in flow of blood
2.
3.
4.
5.
6.
Protection
Sensation
Excretion
Immunity
Synthesis for Vitamin D
Functions of Skin
1. Regulation of body temperature
2. Protection
– Barrier from abrasion, bacteria, dehydration, UV
radiation
3.
4.
5.
6.
Sensation
Excretion
Immunity
Synthesis for Vitamin D
Functions of Skin
1. Regulation of body temperature
2. Protection
3. Sensation
– Nerve endings detect stimuli
4. Excretion
5. Immunity
6. Synthesis for Vitamin D
Functions of Skin
1.
2.
3.
4.
Regulation of body temperature
Protection
Sensation
Excretion
– Small amounts of water, salts, etc excreted by
sweat glands
5. Immunity
6. Synthesis for Vitamin D
Functions of Skin
1.
2.
3.
4.
5.
Regulation of body temperature
Protection
Sensation
Excretion
Immunity
– Langerhans cells help fight foreign invaders
6. Synthesis for Vitamin D
Functions of Skin
1.
2.
3.
4.
5.
6.
Regulation of body temperature
Protection
Sensation
Excretion
Immunity
Synthesis for Vitamin D
– Exposure to UV radiation initiates synthesis of the
active form on vitamin D (aids in the absorption of
calcium and phosphorus)
Structure of Skin
• Two parts
– Epidermis
• Outer, thinner portion, which is composed of
epithelium (mostly stratified squamous)
– Dermis
• Deeper, thicker part composed of connective tissue
Structure of Skin
• Subcutaneous layer also called hypodermis
which attaches the skin to underlying
structures (deep to dermis)
– Adipose and areolar connective tissue
• Serves as storage for fat
• Contains large blood vessels supplying the skin
• Contains sensory nerve endings sensitive to
pressure
Epidermis
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Avascular
5 layers (strata)
Stratified squamous cells
Keratinocytes produce keratin (tough, fibrous
protein; functions are protection and
durability)
Layers of the Epidermis
From superficial to deep
• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• Stratum basale
Stratum corneum
• Outermost epidermal layer
• Made up of 20-30 cell layers
– Flat, dead keratinocytes
– Constant exposure to friction or pressure leads to
formation of a callus – an abnormal thickening
• Keratinization: cells gain keratin and are
constantly shed and replaced by new cells
Stratum lucidum
• Consists of about 5 layers of clear, flat, dead
cells
• Found only in the thick skin of the palms and
soles
Stratum granulosum
• Contains about 5 layers of flattened
keratinocytes
• Cells contain granules that release lipids,
functioning as a water-repellant
• Upper layers beginning to die
Stratum spinosum
• 8-10 layers of keratinocytes with spiny
projections
• Also contains Langerhans cells and projections
of melanocytes
• Some cell division occurs here
• Receives some nourishment from the dermis
(by diffusion)
Stratum basale
• One row of cells right above dermis
• Cells constantly reproducing through cell
division
– Cells multiply, push up, and become part of more
superficial layers
• Adequate blood supply from dermis
• Melanocytes, Langerhans cells, Merkel cells
Epidermal Layers
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Cats Like Good Smelly Beef
Can Lexie Get Some Band-Aids
Carl Likes Green Soggy Bagels
Clark Loves Going to Sunny Beaches
How does the skin do it?
Cells in the lower strata of the epidermis (mostly in
the stratum basale and some in stratum
spinosum) are constantly undergoing cell division
(millions of new cells made daily) and the new
cells are pushed upward, away from the blood
supply of the dermis to become part of the layers
that are closer to the skin’s surface.
As the cells move upward toward the stratum
corneum, they start to die off and become flatter.
These cells have more protective keratin in them.
Dermis
• Major parts are collagen, reticular fibers (thin
protein fibers that add support), and elastic
fibers
• Two layers
– Papillary layer (loose connective tissue)
– Reticular layer (dense connective tissue)
Papillary Layer
• Directly beneath epidermis
• Connects to it via papillae (finger-like
projections)
Reticular Layer
• Deep to papillary layer
• Contains collagen fibers, Pacinian corpuscles,
sensory receptors, sweat glands, hair follicles,
lymph vessels