INTEGUMENTARY SYSTEM 1

• System consists of the skin and accessory structures, such as hair, glands, and nails.
• Humans: Hair, glands, and nails

  Animals: Skin, Hair(Fur), Feather, Hoof
• FUNCTION OF INTEGUMENTARY SYSTEM


  1. protection
  2. sensation
  3. temperature regulation
  4. vitamin D production
  5. excretion
• The integumentary system has sensory receptors that can detect heat, cold, touch, pressure, and pain.
• The skin plays a major role in regulating body temperature
• When exposed to ultraviolet light, the skin produces a molecule that can be transformed into vitamin D, an important regulator of calcium homeostasis.
• There is no vitamin D in the sun. The one responsible for vitamin D conversion is the enzymes containing the 7 dehydrocholesterol when it receives UV. It is found in the epidermis.
• the sun emits:

  1. UVA
  2. UVB
• UVA - not harmful for skin; responsible for photoaging,
• UVB - harmful; responsible for sunburn.
• Not using sunscreen will let photos enter the skin.
• Sunscreen should be applied 15 min. before sun exposure.
• 2 types of sunscreen

  1. mineral sunscreen
  2. chemical sunscreen
• type of sunscreen: reflects sunlight; has zinc oxide, titanium oxide; for sensitive skin

  mineral sunscreen
• type of sunscreen: turns UV rays into non-damaging heat; avobenzone, oxybenzone, homosalate

  chemical sunscreen
• Small amounts of waste products (sweat) are excreted through the skin and glands.
• Superficial part of the skin

  Stratified squamous epithelium

  Composed of 5 strata

  Contains no blood vessels

  epidermis
• cells in epidermis

  1. melanocytes
  2. langerhans cells
  3. merkel cells
• Melanocytes - produces melanin
• Langerhans cells - part of the immune system
• Merkel cells - found right below the epidermis; associated with nerve endings responsible for detecting light touch and superficial pressure.
• Deep part of the skin

  Where the epidermis rests on

  is a connective tissue composed of two layers

  dermis
• dermis

  Collagen is the main type of protein fiber of the extracellular matrix, but elastic and reticular fibers are also present.
• Collagen holds the skin; when we are young it firmly holds the skin
• subcutaneous tissue

  The dermis rests on the subcutaneous tissue also known as the hypodermis.
• a layer of connective tissue

  not part of the skin but connects skin to underlying muscle or bone.

  subcutaneous tissue
• Most cells of the epidermis are called keratinocytes.
• keratinocytes: They produce a protein mixture called keratin which makes cells more durable.
• Desmosomes hold keratinocytes together.
• The connection between desmosomes and hemidesmosomes provides structural strength to the epidermis because keratinocytes are strengthened internally by keratin fibers.
• Gives the ability to resist abrasion

  keratinocytes
• Strata - is the distinction of transitional stages or keratinization. we have 5 strata:
• Most Superficial stratum of the epidermis.

  25 or more layers of dead squamous cells joined by desmosomes.


  stratum corneum
• consists of cornified cells, with a hard protein envelope, filled with the protein keratin.

  Provides Structural strength due to the keratin in the cells.

  stratum corneum
• Prevents water loss due to lipids surrounding cells.

  Sloughing off most superficial cells resists abrasion.

  stratum corneum
• stratum corneum

  Hard keratin - nails and hair; more durable cells
• Is a thin, clear zone above the stratum granulosum

  3 to 5 layers of dead cells. with indistinct boundaries

  stratum lucidum
• Appears transparent.

  Present in thick skin only.

  stratum lucidum
• stratum lucidum

  Disperses keratohyalin around keratin fibers.
• 2 or 5 layers of flattened, diamond-shaped cells.


  stratum granulosum