Lec 5: Integumentary System

• What tissue type protects deeper tissue?

  Stratified Squamous epithelium with keratin

  
• How does skin regulate body temperature?

  With sweat glands through evaporative cooling

  
• Cutaneous sensations of skin

  Temperature, touch, and pain

  (nerve endings)

  
• Metabolic functions of skin

  synthesis of vitamin D in dermal blood vessels,

  vitamin D precursor for calcium (need Vitamin D to absorb Calcium)

  
• Blood Reservoir (Skin)


  The skin can hold 5% of body's total blood volume.

  
• What can the skin's blood reservoir be used for?

  Can be shunted (pulled from) into general circulation for use by vigorously working muscle and/ or other body organs

  
• Excretion (skin)


  Elimination of nitrogen-containing wastes
• Example of nitrogen-containing waste


  Ammonia, Urea, Uric acid

  
• Skin structure (3 layers of skin)

  Epidermis,

  Dermis,

  Hypodermis

  
• Epidermis structure


  Stratified squamous epithelium with keratin,

  Cells tightly connected together by desmosomes,

  Keratinocytes form several layers,

  5 strata layer

  
• Keratinocyte


  epidermal cell that produces keratin

  
• Strata (stratum)


  layers

  
• 5 strata of epidermis

  stratum basale,

  stratum spinosum,

  stratum granulosum,

  stratum lucidum,

  stratum corneum

  
• Stratum Basale


  Single row of cells that serve as origin of keratinocytes for all superficial strata,

  High mitotic activity,

  Contains melanocytes,

  Bottom of Epidermis

  
• Melanocytes


  cells that produce melanin

  
• What cell type accounts for 10-20% of stratum basale

  melanocytes

  
• Stratum Corneum


  Located at exposed surface skin (most superficial),

  20-30 cell layers thick & accounts for three- quarters of epidermal thickness,

  Protective barrier of dead, durable, and expendable cells

  
• Stratum corneum protective barrier:

  Cells are filled with keratin (literally keratin filled plasma membranes),

  Helps give epidermis its protective properties,

  Thickness varies depending on use (Calluses)

  
• why is the top layer of skin dead

  Because its far from a nutrient source

  
• When do the dead skin cells (keratinocytes) fall off?

  every time you towel dry, change clothes, etc... (basically anything) the dead skin cells fall off

  
• Calluses


  a hardened thickened place on the skin,

  caused by friction and pressure from repeated actions,

  can develop on palms of hands and soles of feet

  
• Glycolipids


  Secreted between cells,

  provides waterproofing and preserves some permeability characteristics on the skin,

  Allows for transdermal medications (nicotine patches, etc.)

  
• Melanin


  A protein,

  Pigment produced by melanocytes,

  Gets packaged in melanosomes and then deposited into keratinocytes in more superficial layers,

  Melanin granules then position themselves on superficial (or sunny) side of keratinocyte nucleus to protect against UV radiation,

  
• Amount of melanosomes produced depends on:

  Amount produced depends on genetics and exposure to sunlight

  
• Melanin packaged into vesicles called:

  Melanosomes

  
• Why doesn't a skin tan last long?

  Lysosomes see melanosomes as an invaders & attack them.

  
• What is critical for melanin production?

  Tyrosinase (acts on the amino acid tyrosine)
• Albinism


  Most common form of albinism is the:

  Failure to produce tyrosinase

  
• Dermis


  Strong, flexible connective tissue

  (leather is made from the Dermis)

  
• The two layers of the Dermis

  Papillary Layer

  Reticular Layer

  
• Papillary Layer


  20% of the Dermis,

  Thin, superficial layer of areolar connective tissue,

  Supports and nourishes overlaying epidermis,

  Projections called Dermal Papillae,

  Pain receptors,

  Capillary loops

  
• Dermal Papillae


  Increases surface area and serves as basis for friction ridges and fingerprints (nipple like projections)

  
• Capillary Loops


  Smaller blood vessels that give blood and nutrients to stratum basale

  
• Nerves with free nerve endings

  Detect pain, hot & cold, light touch

  
• Reticular Layer


  Accounts for 80% of dermis thickness,

  Dense irregular connective tissue with meshwork of collagen and elastic fibers,

  Has blood vessels,

  Glands,

  Nerve receptors

  
• Hypodermis (subcutaneous)


  Technically not part of the skin,

  Anchors skin to underlying organs,

  Composed mainly of adipose tissue (accounts for half of the body's stored fat)

  
• Lamellar Corpuscle


  Deep pressure receptors

  
• Sebaceous glands


  Produces oil (sebum) (softens & lubricates hair & skin),

  Most with ducts that empty into hair follicles,

  Distributed body wide except for palms of hands and soles of feet,

  Activated at puberty (under hormonal control)

  
• Sebaceous glands are clinically known to cause:

  Acne
• How does accutane work?

  It shuts down the sebaceous glands,

  It stops mitosis*

  Accutane is a teratogenic