The Integumentry system
Anatomy & Physiology chapter 5
Introduction to structures of the Integument and their functions
• Skin = organ system,
• largest, most accessible, very underappreciated
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Integumentary system aka the integument
16% of total body weight (or 10-20 lbs)
1.5 – 2 m2
Defense from
• abrasion, UV radiation, environmental chemicals, microbes,
dehydration
• 1st line of defense
• 2 major parts:
• cutaneous membrane and
• accessory structures
• Cutaneous membrane
• Epidermis
• Superficial epitheilium (tissue)
• Avascular – short distance from dermis for diffusion
• Keratinocytes; thin skin, 4 layers, 0.08mm
• 4 layers are stratum corneum, stratum lucidum, stratum granulosum and
stratum spinosum
• Palms and soles have thick skin, 0.5mm
• Dermis underlying connective tissues
• Lots of blood vessels
• Sensory receptors
• Hypodermis (loose connective tissue to other structures like muscles)
• Accessory structures
• Hair
• Nails
• Exocrine glands
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Functions *****
• Protection
• Against impact, abrasion, chemicals, fluid loss (hydration !)
• Excretion
• Salts, water and organic wastes
• Maintenance of temperature
• Evaporative cooling
• Production of melanin
• Requires UV light
• Production of keratin
• Water repellant
• Synthesis of vitamin D
• Hormones related to calcium use
• Storage of lipids
• adipocytes
• Sensation
• Touch, pain, pressure and temperature sensors of nervous sysem
Figure 5-1 The Components of the Integumentary System
Accessory Structures
Cutaneous Membrane
Hair shaft
Epidermis
Pore of sweat
gland duct
Papillary layer
Tactile corpuscle
Dermis
Reticular layer
Sebaceous gland
Arrector pili muscle
Sweat gland duct
Hair follicle
Lamellated corpuscle
Hypodermis
Nerve fibers
Sweat gland
Artery
Vein
Fat
Cutaneous
plexus
Pigmentation
• Carotene
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Orange yellow pigment
found in dermis
Found in fruits and vegetables
Converted to vitamin A – needed for skin and photoreceptor pigments
• Melanin
• Brown, yellow brown or black
• In stratum basale and stratum spinosum, may last until stratum
granulosum
• Ratio of melanocytes to basal cells can range from 1:4 – 1:20
• Freckles and darker complexions making more melanin, not more cells
• Useful in reflection UV radiation, more melanin produced in response
to UV exposure, last about 10 days
Dermal Circulation
• Lots of blood vessels in skin
• Regulation of temperature, and
• delivery of oxygen and nutrients
• Removal of toxins
• Redder skin when vessels are dilated, almost white (or blue) when
constricted – most obvious in thinnest skin like lips and nails
• Jaundice – liver function, bile not excreted, yellowish tone to skin
• Pituitary tumors – excess melanin production
• Addison’s disease – also related to pituitary function and melanin
• Vitiligo- loss of melanocytes and sudden/ complete loss of pigment
Vitamin D
• Too much sun is bad but …..
• UV radiation needed to make melanin – relation to other
pigments
• UV radiation also needed to convert cholecalciferol into
Vitamin D3; used with Calcitriol to control calcium
concentrations at kidney level and in small intestine
• Calcium is absorbed in small intestine
• Calcium needed for bone growth and structure, including teeth
• Calcium also part of muscle contraction process
Skin Cancer
• Moles and warts are benign tumors and viruses
• Skin cancer most common form of cancer
• Very dangerous
• Melanoma detection
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A asymmetry
B
border
C color
D diameter (5 mm or 0.02 in)
The Dermis
• Between epidermis and hypodermis
• Epi = above
• Hypo = below
• 2 major components
• Papillary layer
• Projections (papilli) into epidermis layer
• Contains blood vessels, lymph vessels
• Nerve endings
• Made of areolar tissue (CT)
• Reticular layer
• Mesh or network of reticular tissue (CT)
• Holds dermis to hypodermis
• Lots of collagen and elastic fibers
• Dermatitis
• Irritations and infections of this layer are really painful (poison ivy)
Hair
• 2.5 million hairs ( only 500,000 on head)
• 75% on surface of body and not on head
• Vellus hairs on body
• Terminal hairs on head
• Produced by hair follicles
• Grow for 2-5 years and are shed
• Actually have many roles
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Protect from UV radiation
Cushion
Insulate
Guard from foreign particles and insects
Eyelash – keep sweat out of your eyes
Sensory receptors
• Nerves at each follicle can cause goosebumps,
Glands
• Sebaceous glands
• Make oil (sebum)
• Sweat glands
• Apocrine – associated with hair follicles
• Stinky and sticky sweat
• Merocrine – directly onto surface
• Cooling
• Water, electrolytes and metabolized drugs
• Protect from environmental chemicals
• Mammary glands are also related to apocrine glands and are part of
integument….
nails
• Lots of sensation at finger tips
• Exposed dorsal tips
• Protect from mechanical/ physical stress
• Deepest part close to bone !
• Body of nail is dead cells packed with keratin
• Nails reflect health and can have discoloration or ridges
based on disease and/or malnutrition.
Injury Repair
• Clot/ scab starts internally
• Granulation tissue is next
• Dermal recovery
• Epithelial cells replaced
• Enhanced circulation
• Finally scar tissue
• Highly fibrous
• Fewer capillaries
• Follicles, glands and nerves are not repaired