PHYSIOLOGY CHAPTER 5: SKIN

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PHYSIOLOGY CHAPTER 5SKIN THE INTEGUMENTARY
SYSTEM
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4 TYPES OF MEMBRANES?

• 1) serous membranes
• line body cavities that dont open to the outside
• location thorax, abdomen the organs within
• made of simple squamous epithelium loose CT

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4 TYPES OF MEMBRANES?

• 1) serous membranes
• Pleura serosa lining the thoracic wall lungs
• Pericardium serosa enclosing the heart
• Peritoneum serosa lining abdominopelvic cavity
  viscera

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4 TYPES OF MEMBRANES?

• 2) mucous membranes
• line cavities tubes that open to the outside
• location oral nasal cavities, tubes of the
  digestive, respiratory, urinary, reproductive
  systems
• made of epithelium w/ goblet cells
  loose CT
• secrete mucus

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4 TYPES OF MEMBRANES?

• 3) synovial membranes
• location the inner linings of synovial joint
  cavities
• made of dense CT loose CT adipose tissue
• secrete synovial fluid to lubricate
  joints

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4 TYPES OF MEMBRANES?

• 4) cutaneous membranes
• Skin
• Dry because it is exposed to air

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INTRODUCTION?

• integumentary system skin accessory organs
  (hair, nails, sweat oil glands)
• hyperhidrosis a condition of profuse,
  uncontrollable, unpredictable sweating

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SKIN ITS TISSUES?

• skin is a large organ vital to maintaining
  homeostasis
• Skin stats
• Surface area 1.2 to 2.2 square meters
• Weight 9 to 11 pounds
• Accounts for 7 of an adults total body weight
• 1.5 to 4 mm thick in various parts of the body
• Integument covering

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functions of skin

• Protection chemical, physical, biological
• regulates body temperature
• Insulation fat storage
• prevents water loss from deeper tissues

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functions of skin

• houses sensory receptors sensitive to pain,
  temperature, touch, pressure
• makes biochemicals such as vitamin D
• excretes some waste
• Blood reservoir has an extensive vascular supply

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2 layers of skin

• epidermis outer layer made of stratified
  squamous epithelium

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2 layers of skin

• dermis thicker inner layer made of connective
  epithelial tissue, smooth muscle, nervous tissue,
  blood

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2 layers of skin

• the 2 layers are separated by the basement
  membrane (areolar c.t.)

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• a subcutaneous layer (sub Q, hypodermis) made of
  loose CT adipose tissue binds the skin to the
  organs under it

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Epidermal cells

• Keratinocytes
• make keratin
• Melanocytes
• make melanin
• Merkel cells
• touch receptors
• Langerhans cells
• macrophages

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EPIDERMIS

• 4 layers on most of the body
• stratum basale base layer
• stratum spinosum prickly layer, keratinocytes
  are flatter and appear spiny
• stratum granulosum granular layer, granules
  form keratin in the upper layers and provide
  waterproofing

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EPIDERMIS

• 4 layers on most of the body
• stratum corneum horny layer
• A 5th layer on only thick skin
• - stratum lucidum clear layer, can only be
  found on palms soles (thick skin), a row of
  thin, flat, dead keratinocytes

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EPIDERMIS

• the deepest layer of the epidermis, the stratum
  basale (basal layer), contains cells that divide,
  mainly young keratinocytes

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EPIDERMIS

• epidermal cells undergo keratinization as they
  mature are pushed toward the surface
• the outermost layer, the stratum corneum (horny
  layer), is made of dead epidermal cells which are
  eventually shed
• 40 pounds in an average lifetime!
• Cornu horn
• Totally new epidermis in 25-45 days!

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EPIDERMIS

• the rate of cell division increases where skin is
  rubbed off regularly forming calluses corns
• the epidermis protects underlying tissues against
  water loss, injury, the effects of harmful
  chemicals

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EPIDERMIS

• melanin protects cells from the effects of UV
  light
• melanocytes (cells that make melanin) transfer
  melanin to epidermal cells which determines skin
  color

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SKIN COLOR

• genetically determined
• varies based on the kind amount of melanin
  produced, since all people have about the same
  number of melanocytes

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SKIN COLOR

• influenced by environment (exposure to sun),
  chemically induced photosensitivity (some meds,
  perfumes, detergents, limes, celery)
• influenced by physiological factors (blood color,
  diet, chemicals such as bilirubin)
• 3 pigments affecting skin color melanin,
  carotene, hemoglobin

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DERMIS

• Composed of strong, flexible c.t.
• Corresponds to animal hides used to make leather
• dermis binds the epidermis to underlying tissues
• has 2 layers
• Papillary
• reticular

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DERMIS

• fingerprints result from epidermal ridges
  projecting inward dermal papillae projecting
  upward
• genetically determined
• increase friction enhance gripping ability

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DERMIS

• dermal blood vessels supply nutrients to all skin
  cells help regulate body temperature
  (vasoconstriction, vasodilation)
• the dermis also contains hair follicles, sweat
  glands, sebaceous (oil) glands

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DERMIS

• nerve fibers are scattered throughout the dermis
• some carry impulses to muscles glands
• some are associated with sensory receptors in the
  skin, they carry impulses to the brain spinal
  cord

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DERMIS
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SUBCUTANEOUS LAYER

• made of loose CT adipose tissues
• it helps supply the skin with blood
• the adipose tissue helps conserve body heat

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ACCESSORY ORGANS OF THE SKIN?

• hair
• hairs develop in the follicles
• new cells push older cells closer to the surface
  where they become keratinized die
• hair color is genetically determined
• an arrector pili muscle attaches to each hair
  follicle this pulls the hair erect when
  stimulated goose bumps

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Functions of hair?

• To sense insects on skin
• Guards against physical
• trauma, heat loss, sunlight
• Eyelashes shield eyes
• nose hairs filter large particles from air

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ACCESSORY ORGANS OF THE SKIN?

• sebaceous glands
• holocrine glands that secrete sebum a mix of
  oil cellular debris. Cells rupture.
• sebum keeps skin hair soft, pliable,
  waterproof
• acts as a
• bactericide
• function begins
• at puberty

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ACCESSORY ORGANS OF THE SKIN?

• sweat glands sudoriferous glands
• exocrine glands which consist of a coiled tube
• eccrine / merocrine sweat glands respond to
  elevated body temp.hands, feet, forehead
• apocrine sweat glands respond to pain or
  emotional stress, function begins at puberty,
• armpits, anogenital areas

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ACCESSORY ORGANS OF THE SKIN?

• modified sweat glands include mammary glands
  ceruminous glands in the outer ear canal
• 2.5 million, most in palms, soles, forehead

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Apocrine sweat gland eccrine sweat gland
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ACCESSORY ORGANS OF THE SKIN?

• nails
• protective coverings for fingers toes
• each nail consists of a nail bed nail plate
• the white moon-shaped lunula at the base of the
  nail plate is the area where cells are most
  actively dividing
• again, cells become keratinized die as they age

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REGULATION OF BODY TEMPERATURE?

• vital because heat affects the rate of metabolic
  reactions
• heat is a product of metabolism
• skin constantly loses heat to the air

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REGULATION OF BODY TEMPERATURE?

• If temp is too high
• dermal blood vessels dilate
• sweat glands secrete sweat
• if temp is too low
• dermal blood vessels constrict
• sweat glands deactivate
• skeletal muscles contract involuntarily
  shivering

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HEALING OF WOUNDS?

• skin injuries trigger inflammation (red, warm,
  swollen, tender)
• dividing epithelial cells fill in shallow cuts
• clots close deeper cuts

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HEALING OF WOUNDS?

• scabs clots dried tissue
• scars result from connective tissue replacing
  skin
• granulations form in large open wounds

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Wound healing
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HEALING OF WOUNDS?

• Wound healing can be differentiated into three
  major phases
• Inflammatory phase (1) The wound is rinsed by
  blood and filled with blood-collagen and fibrin
  constituents.
• Proliferative phase (2)Resorption of
  blood-collagen and reepithelialization. The
  reepithelialization is a movement of the
  surrounding epithelial cells to close the wound.
• Maturation and remodeling phase (3) Growth of
  new epithelial cells.

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Homeostatic imbalances of skin

• Skin cancer?
• Basal cell carcinoma least malignant most
  common 30 of all white people get it
• Squamous cell carcinoma - often on scalp hands,
  grows rapidly and metastasizes
• Melanoma cancer of melanocytes, most dangerous
  type
• ABCD rule
• Asymmetry, border irregularity, color, diameter

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• Burns
• 1st degree epidermis is damaged
• ex. sunburn
• 2nd degree epidermis part of the dermis are
  damaged, blisters occur
• 3rd degree epidermis dermis hypodermis are
  all damaged, nerve endings are destroyed
• Evaluated by the rule of nines

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Effects of aging

• 1) Skin thins
• 2) Lubricating substances become deficient, so
  skin gets dry itchy
• 3) Elastic fibers clump, skin loses elasticity
• 4) Sub Q fat layer diminishes, often cold
• 3 4 cause wrinkles
• 5) Less melanocytes Langerhans cells enhance
  the risk of skin cancer
• 6) Hair thins due to fewer active hair follicles

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Name that skin disease!!!!
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