Miscellaneous information

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Miscellaneous information

• Skin is the largest organ in the body
• It is the first line of defense against infection
• It retards water loss and regulates body
  temperature
• It houses sensory receptors, contains immune
  system cells, and excretes small quantities of
  wastes.

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Layers

• Skin has two distinct layers
• The top or outer layer is called epidermis (epi
  always means above), and consists of stratified
  squamous epithelium
• The inner layer is dermis (connective tissue
  layer) is separated from the epidermis by a
  basement membrane
• The dermis contains connective tissue, blood,
  smooth muscle, nervous tissue, collagenous and
  elastic fibers

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The skin
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Epidermis

• Mitosis occurs in deepest layer (closest to the
  basement membrane due to the lack of blood in the
  epidermis)
• Diffusion from the dermal blood vessels supplies
  nutrients to this layer
• Epidermis is thickest on soles of feet and palms
  of hands and contains 5 zones
• The rest of the epidermis contains 4 zones (thin
  skin0.10 to 0.15 mm)
• Thin skin has less sensory receptors than thick
  skin, has hair and sebaceous glands, but less
  sweat glands than thick skin

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Layers of Epidermis

• Basal layer is called stratum basale (mitosis
  occurs here)-single row of cuboidal or columnar
  keratinocytes, also have melanocytes and Merkel
  cells scattered in this layer
• Next up toward surface is stratum spinosum (8-10
  layers that look spiny when stained). Have
  Langerhans cells and melanin granules too
• Next is stratum granulosum (3-5 layers of
  flattened keratinocytes that are dying
  (apoptosis-genetically programmed cell death)

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Continued..

• Next is the stratum lucidum (3-5 layers of clear,
  flat, dead keratinocytes with lots of keratin
  protein (only in thick skin)
• Top layer is stratum corneum contains 25-30
  layers of dead, flat keratinocytes, that are
  shed and replaced by cells from deeper layers.

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Epidermis
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Specialized cells in epidermis

• Melanocytes-produce darks pigment (melanin) that
  provides color of skin (and hair) and protects
  from U.V. light, found in deepest layer
• Keratinocytes-90 of all cells in the epidermis
  produce keratin that waterproofs and protects
  skin
• Langerhans cells interact with white blood cells
  and protect from infection (easily damaged by
  sunshine)
• Merkel cells are found in stratum basale and
  function in touch by contacting the flattened
  process of a sensory nerve called a Merkel disc.

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Rashes

• Chicken pox begins with tiny red pustules that
  start on back, chest, and scalp then spread, form
  blisters, crust, then heal
• Fifth disease begins with slapped cheek
  appearance, then red spots cover entire body
• Lyme disease may have a bulls-eye rash spreading
  out around tick bite
• Scarlet fever has a rash like a sunburn with
  goosebumps, spreads over entire body, skin may
  peel.

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Dermis- this is the hide

• Second, deeper part of skin
• Has collagen and elastin fibers
• Also blood vessels, nerves, glands, and hair
  follicles, muscle fibers, sebaceous glands and
  sweat glands
• 2 regions papillary region and dermal region

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Dermis-papillary region

• 1/5 of thickness, has areolar connective with
  fine elastic fibers
• Surface area of this region increased by dermal
  papillae which indent the epidermis in conical
  ridges
• Epidermal ridges are downward projections of
  epidermis between the papillae and increase
  surface area of epidermis
• Both of these are responsible for finger prints
  (which help with friction)
• Dermal papillae also have blood capillaries,
  Meissners corpuscles, and free nerve endings

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Dermis-reticular region

• Lower 4/5th of dermis
• Attaches to hypodermis
• Has dense irregular connective tissue with
  collagen and course elastic fibers
• Has hair follicles, nerves, sebaceous glands, and
  sweat glands
• Collagen bundles and elastic fibers provides
  strength, extensibility, and elasticity of skin
• Extreme stretching causes striae (stretch marks)

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Subcutaneous layer

• Also called hypodermis
• Not a layer of the skin
• Contains loose connective tissue and adipose
• Also has the major blood vessels that supply the
  skin
• When you gain weight, this layers gets thicker

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Accessory organs

• Hair follicles are where hair develops from
• Nails are protective coverings for the ends of
  the fingers and toes
• Skin glands include sebaceous glands, sweat
  glands, and ceruminous glands

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Hair

• Not on palms, soles, around nipple and genitals
• Hair follicles extend from the surface into the
  dermis and contains a hair root. As epidermal
  cells at the base are nourished they reproduce
  and grow, causing older cells to push toward
  surface, become keratinized and die
• Hair shaft is the part of hair that is exposed to
  above the surface

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Hair shape

• Straight hair has a round shaft (in transverse
  section)
• Wavy hair is oval
• Curly hair is kidney shaped
• Shaft and root of hair have 3 layers medulla
  has pigment and air spaces, cortex has pigment in
  dark hair, but air in white or grey hair, cuticle
  is outermost layer and is a single layer of
  heavily keratinized cells arranged like shingles.

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Hair continued

• Follicle surrounds the root
• The hair will eventually be shed and new ones
  replace them (scalp hair typically grows for 2 to
  6 years and rests for 3 months before growing new
  hair)
• 85 of scalp hairs are in the growth phase
• The matrix in the hair bulb is the area where
  cell division occurs

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2 types of hair

• Vellus hair is the fine hair (peach fuzz) on
  children and females (arms, legs, etc)
• Terminal hair is course hair found on head,
  eyebrows, beards, pubic area, underarms.

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Hair color

• Due to amount and type of melanin in cells
• Dark hair has true melanin
• Blonde and red contain variants of melanin
  containing more iron and more sulfur
• Gray is caused by a decline in melanin production
• White hair lacks melanin and has air bubbles in
  hair shaft

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Sebaceous glands

• Associated with hair follicles
• Not found on palms and soles
• Produce sebum (oil)
• Helps keep skin and hair soft, pliable, and
  waterproof (prevents excessive evaporation also)
• Acne is caused by excess sebum production

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Sweat glands or sudoriferous glands

• Eccrine sweat glands are most numerous and
  respond to body temperature ( more on forehead,
  palms and soles produce 600 mL of sweat per day)
• Apocrine sweat glands develop a scent as the
  secretion is metabolized by bacteria and also
  often called the scent gland
• Apocrine activate after puberty and are located
  in arm pit, groin, and around nipples, and
  bearded areas of face in adult males. (cold
  sweat!)

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Modified glands

• Ceruminous glands are modified sweat glands
• These are located in external ear canal and
  secrete cerumin (ear wax)
• Mammary glands are also modified sweat glands
  that secrete milk

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Nails

• Each has nail body, free edge, and nail root
• Nail body is visible portion
• Free edge extends past the distal end of the
  finger or toe
• Nail root is buried in a fold of skin
• Whitish semicircle is lunula
• Nail matrix is growth area
• Nails grow 1 mm per week (fingers) and slower in
  toes

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Regulation of Body temperature

• Primary means of body heat loss is radiation
  where infrared heat rays escape from warmer
  surface to cooler ones
• Conduction occurs as heat moves from the heat of
  the body directly into the molecules of cooler
  objects in contact with its surface (you sit in a
  chair, the chair gets some of your heat)

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Other methods of heat loss

• Convection is when the air circulating near the
  body becomes warmer and moves away from the body
  and is replaced by cooler air moving toward the
  body
• Evaporation is when eccrine sweat glands activate
  and cause sweating, which is evaporated into the
  air, carrying heat away from the skin surface

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Skin color

• Genetic factors-how much melanin is produced
• Environmental factors-sunlight and X-rays darken
  skin color by increasing melanin production
• Carotene is yellow/orange and is a precursor of
  vitamin A
• Physiological factors include blood in skin
  (hemoglobin)
• If well oxygenated skin is pink in light skinned
  people
• Poor oxygen concentration results in a bluish
  tint (cyanosis)

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Healing

• If cuts in skin are shallow the epidermal cells
  are stimulated to divide and fill in the cut (no
  scar)
• If cuts are deeper a clot forms in the wound
  first, followed by a scab that protects the
  underlying tissues
• Fibroblast migrate in to produce new collagenous
  fibers that bind the edges of the wound together
• Phagocytic cells remove dead cells and debris
• Scars form if wound is extensive ( due to
  connective tissue)

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Burns

• First degree- quick healing, no permanent
  scarring (light sunburn for example)
• Second degree-destroys epidermis and some dermis
  blister appear from escaped fluids, results from
  touching hot objects usually recover completely
  with no scar
• Third degree-Full thickness burns destroys
  epidermis, dermis, and accessory organs of skin
• Usually third degree require grafting of skin and
  will leave permanent scars

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Skin Disorders (look up definitions in text or
web)

• Athletes foot
• Birthmark
• Boil
• Carbunmcle
• Cyst
• Eczema
• Erythema
• Herpes
• Keloid (scar)

• Mole
• Pediculosis
• Pruritus
• Pustule
• Scabies
• Seborrhea
• Ulcer
• Urticaria
• wart

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Which systems does integumentary interact with?

• http//www.sciencenetlinks.com/interactives/integs
  ystem_resource.html
• Go here for the answer!
• Can you find more?