Chapter 5: The Integumentary System

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Chapter 5 The Integumentary System
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What are the structures and functions of the
integumentary system?
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Integument

• Considered one organ or organ system
• the largest system of the body
• 16 of body weight
• Most varied in function
• Covering, 1st line of defense

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Components of the Integument

• made up of 2 parts
• cutaneous membrane (skin)
• accessory structures

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Parts of the Integumentary System
Figure 51
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Parts of the Cutaneous Membrane

• Outer epidermis
• superficial epithelium (epithelial tissues)
• Inner dermis
• connective tissues

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The Subcutaneous Layer

• Subcutaneous layer (hypodermis)
• loose connective tissue
• below the dermis

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Accessory Structures

• Originate in the dermis
• Extend through the epidermis to skin surface
• hair
• nails
• exocrine glands

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Functions of Skin

• Protection
• Excretion (glands)
• Maintains body temperature
• Synthesizes vitamin D3
• Storage
• Sensory information

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What are the main structures and functions of
the epidermis?
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Epidermis

• Avascular stratified squamous epithelium
• Nutrients and oxygen diffuse from capillaries in
  the dermis
• Keratinocytes
• contain large amounts of keratin
• the most abundant cells in the epidermis

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Organization of the Epidermis
Figure 52
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• Thin Skin
• Covers most of the body
• Has 4 layers of keratinocytes
• Thick Skin
• Covers the palms of the hands and soles of the
  feet
• Has 5 layers of keratinocytes

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Layers of the Epidermis

• From basal lamina to free surface
• stratum germinativum
• stratum spinosum
• stratum granulosum
• stratum lucidum
• stratum corneum

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Stratum Germinativum

• The germinative layer
• is attached to basal lamina
• has many germinative basal cells (stem cells)
• Sensory Merkel cells and melanocytes
• Epidermal ridges
• forms a strong bond between epidermis and dermis

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Stratum Spinosum

• The spiny layer
• produced by division of stratum germinosum
• 810 layers of keratinocytes bound by desmosomes
• cells shrink until cytoskeletons stick out
  (spiny)
• Langerhans cells

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Stratum Granulosum

• Stops dividing, starts producing
• keratin
• a tough, fibrous protein
• makes up hair and nails
• keratohyalin
• dense granules
• cross-link keratin fibers

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Stratum Lucidum

• The clear layer
• found only in thick skin
• covers stratum granulosum
• Dead keratinocytes

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Stratum Corneum

• exposed surface of skin
• 15 to 30 layers of keratinized cells
• water resistant
• shed and replaced every month
• dead, protective cells filled with keratin
• on all exposed skin surfaces except eyes

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Perspiration

• Insensible perspiration
• interstitial fluid lost by evaporation through
  the stratum corneum
• Sensible perspiration
• water excreted by sweat glands

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What causes different skin colors?
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Skin Color

• Skin color depends on
• the pigments carotene and melanin
• blood circulation (red cells)

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Carotene

• Orange-yellow pigment
• Found in orange vegetables
• Accumulates in epidermal cells and fatty tissues
  of the dermis
• Can be converted to vitamin A

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Melanin

• Yellow-brown or black pigment
• Produced by melanocytes in stratum germinativum
• Stored in transport vesicles (melanosomes)
• Transferred to keratinocytes
• Skin color depends on melanin production, not
  number of melanocytes

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Function of Melanocytes

• Melanin protects skin from sun damage
• Ultraviolet (UV) radiation
• causes DNA mutations and burns which lead to
  cancer and wrinkles

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Melanocytes
Figure 55
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Capillaries and Skin Color

• Oxygenated red blood contributes to skin color
• blood vessels dilate from heat, skin reddens
• blood flow decreases, skin pales
• Cyanosis

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Vitamin D

• Epidermal cells produce cholecalciferol (vitamin
  D3)
• in the presence of UV radiation
• Liver and kidneys convert it into calcitriol
• aids absorption of calcium and phosphorus
• Insufficient vitamin D
• can cause rickets

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Epidermis Summary

• The epidermis
• is a multilayered, flexible, self-repairing
  barrier
• prevents fluid loss
• protects from UV radiation
• produces vitamin D3
• resists abrasion, chemicals, and pathogens

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What are the structures and functions of the
dermis?
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The Dermis

• Is located between epidermis and subcutaneous
  layer
• Anchors epidermal accessory structures (hair
  follicles, sweat glands)
• Has 2 components
• outer papillary layer
• deep reticular layer

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The Papillary Layer

• Consists of areolar tissue
• Contains smaller capillaries, lymphatics, and
  sensory neurons
• Has dermal papillae projecting between epidermal
  ridges
• Dermatitis

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The Reticular Layer

• Consists of dense irregular connective tissue
• Contains larger blood vessels, lymph vessels, and
  nerve fibers
• collagen and elastic fibers extending into
  papillary layer

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Characteristics of Dermis

• Strong, due to collagen fibers
• Elastic, due to elastic fibers
• Flexible (skin turgor) stretches without damage

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Skin Damage

• Sagging and wrinkles (reduced skin elasticity)
  are caused by
• dehydration
• age
• hormonal changes
• UV exposure
• Pregnancy/weight gain

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Lines of Cleavage

• Collagen and elastic fibers in the dermis
• are arranged in parallel bundles
• resist force in a specific direction
• Surgical landmark

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Dermis Summary

• The dermis
• provides mechanical strength, flexibility and
  protection
• is highly vascularized
• contains many types of sensory receptors

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What are the structures and functions of the
subcutaneous layer?
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The Hypodermis

• The subcutaneous layer or hypodermis
• lies below the integument
• stabilizes the skin
• made of elastic areolar and adipose tissues
• connected to the reticular layer of integument by
  connective tissue fibers

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Accessory Structures

• Hair, hair follicles, sebaceous glands, sweat
  glands, and nails
• are located in dermis
• project through the skin surface

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What determines hair growth, texture, and color?
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Location of Hair

• Originate in small organs called follicles
• The human body is covered with hair, except
• palms
• soles
• lips
• portions of external genitalia

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Functions of Hair

• Protects and insulates
• Guards openings against particles and insects
• Is sensitive to very light touch

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Accessory Structures of Hair

• Arrector pili
• involuntary smooth muscle
• Root Hair Plexus
• Sensory nerves around follicle

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Types of Hairs

• Vellus hairs
• soft, fine
• cover body surface
• Terminal hairs
• heavy, pigmented
• head and eyebrows
• other parts of body after puberty

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What are the skin glands and secretions?
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Exocrine Glands

• Sebaceous glands (oil glands)
• holocrine glands
• secrete sebum
• Sweat glands
• merocrine glands
• watery secretions

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Sebaceous Glands
Figure 510
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Types of Sweat Glands

• Apocrine
• found in armpits, around nipples, and groin
• Merocrine secretions
• Merocrine
• widely distributed on body surface
• especially on palms and soles
• sensible perspiration

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Other Integumentary Glands

• Mammary glands
• produce milk
• Ceruminous glands
• protect the eardrum
• produce cerumen (earwax)

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What is the function of nails?
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Nail Functions

• Nails protect fingers and toes
• made of dead cells packed with keratin
• metabolic disorders can change nail structure

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Skin Cancer

• Types of Skin Cancer
• Basal cell carcinoma
• Most common, least malignant
• Squamous cell carcinoma
• Less common, grows rapidly, seldom metastasize
• Malignant melanoma
• Most dangerous, spread throughout lymphatic
  system

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Skin Cancer
Figure 56