integumentary system

• epidermis: outer layer of skin
• stratum basale: deepest layer

  • nourished by blood from dermis
  • stem cells divide and daughter cells move up
  • nutrients decrease, cells die
• stratum spinous: stretchy layer

  • anchoring junctions (desmosomes): intermediate filaments attach to cells and keep them from stretching apart
• stratum granulosum: transform

  • cells flatten and nuclei/organelles disintegrate
  • keratinization: cells fill with keratin
  • release water resistant to glycolipids
• stratum lucidum: thin layer

  • dead keratinocytes
  • keratinization partially complete
• stratum corneum: outer layer

  • thick layer of keratinocytes
  • keratin: tough, fibrous protein protects skin from abrasion and penetration
  • glycolipids: waterproof cells
• callus: thickened area of keratinized skin
• keratinocytes: skin cell

  melanocytes: pigment cells

  • found in stratum basale
• melanin: pigment

  • absorb UV radiation
  • protect from DNA damage
• melanosomes: pigment granules

  • can transfer to keratinocytes
• dermis inner layer

  • papillary layer: thin
  • dermal papillae: uneven projections, ridges are most prominent hands/feet
• areolar tissue: interlacing collage and elastic fibers loosely woven
• dermal blood vessels

  • supply nutrients to skin cells
  • regulate body temp

  dilate to release heat: more flow to skin

  constrict to retain heat: less flow to skin
• reticular layer: thick

  • dense irregular connective tissue: closely packed bundles of interlacing collagen fibers
  • collagen, elastic fibers, reticular fibers