Integumentary System

• Integumentary System (Integument)


  Composed of skin, hair, nails, sweat glands, oil glands, & mammary glands
• Integumentary System Functions


  • Physical protection
  • Regulation of body temperature (sweating, vasodilation/vasoconstriction)
  • Excretion (secretion)
  • Nutrition (synthesis of Vitamin D precursor)
  • Sensation (via sensory receptors)
  • Immune defense
• Skin


  Cutaneous membrane composed of epidermis (stratified squamous epithelium) and dermis (underlying loose CT)

  
• Integumentary Tissues


  • All 4 tissue types are present: epithelium covers the surface, CT provides underlying stability, abundant blood vessels, neural tissue provides sensation and controls blood vessel diameter

  
• Epidermal Cell Types


  • Keratinocytes
  • Melanocytes
  • Merkel cells
  • Langerhans cells
• Epidermal Layers


  1. Stratum germinativum (stratum basale)

  2. Stratum spinosum

  3. Stratum granulosum

  4. Stratum lucidum (only in thick skin)

  5. Stratum corneum
• Thick vs Thin Skin


  Relative epidermal thickness
• Dermis


  Has 2 parts: papillary layer and reticular layer
• Hypodermis


  Also known as subcutaneous layer or superficial fascia
• Hair Follicles


  • Hair forming organs of epidermal origin
  • Hair is a nonliving, keratinized structure that extends past the skin surface
• Hair Growth Cycle


  Active (growth) and Resting stages
• Hair Layers

  • Medulla (inner, soft keratin)
  • Cortex (outer, hard keratin)
  • Cuticle (outer layer of dead cells)
• Sebaceous and Sweat Glands

  Skin glands
• Nails


  • Nail production occurs at the nail root
  • Eponychium is also known as the cuticle
• Epidermis consists of stratified squamous epithelium with five layers: stratum basale, spinosum, granulosum, lucidum, corneum.
• Skin has three layers: epidermis (outermost), dermis (middle layer), hypodermis/subcutaneous tissue (deepest).
• The integumentary system is the largest organ system, consisting of skin, hair, nails, glands, and sensory receptors.
• Stratum Spinosum - contains spiny projections called spinules
• Stratum Basale - deepest layer, contains melanocytes which produce pigmentation
• The skin's primary function is protection against physical injury, infection, dehydration, UV radiation, and temperature extremes.
• Stratum Granulosum - contains keratohyalin granules
• The skin contains sensory receptors that detect touch, pressure, pain, heat, cold, itch, tickle, vibrations, and movement.
• Stratum Lucidum - thin transparent layer found only on palms and soles
• Stratum Granulosum - cells become flattened and contain keratin
• Dermal papillae are finger-like extensions that anchor the epidermis to the dermis.
• Diseases that affect the integumentary system can be caused by genetic factors, environmental factors, infectious agents, autoimmune disorders, nutritional deficiencies, hormonal imbalances, aging, and trauma.
• Functions of the integumentary system include protection against physical injury, pathogens, UV radiation, water loss, and temperature extremes; regulation of body temperature through sweating or vasoconstriction/vasodilation; sensation of touch, pain, pressure, vibration, and temperature; secretion of sebum to lubricate skin and prevent dehydration; excretion of waste products such as urea and lactic acid; synthesis of vitamin D from cholesterol when exposed to sunlight; and storage of fatty acids and energy reserves.
• The skin regulates body temperature through vasoconstriction or vasodilation of blood vessels.
• Stratum Lucidum - found only in thicker skin, appears clear due to flattened cells with no nuclei or cytoplasm
• Skin color varies due to differences in the amount and distribution of melanin produced by melanocytes.
• Stratum Granulosum - cells become flattened and contain keratin filaments
• Stratum Corneum - outermost layer, composed of dead keratinized cells that are constantly being shed and replaced by new ones
• Nails protect the tips of fingers and toes and aid in grasping objects.
• Dermal papillae are finger-like extensions that anchor the epidermis to the underlying connective tissue.
• Stratum lucidum


  Only in thick skin, present in palms & soles, cells similar to those in granulosum but do not stain well = "clear layer"

  
• Stratum corneum


  Surface layer, dead cells, 5-30 layers of flattened, dead, interlocking cells, connected cells are shed in sheets

  
• Keratinized skin (cornified)


  Epithelium containing a large amount of keratin, everywhere on skin surface, except eyelids

  
• Epidermal ridges


  • Form complex whorls in thick skin (e.g., fingerprints)

  
• Skin color


  Determined by multiple factors, including pigments, such as melanin (of which there is more than one type)
• Stratum spinosum


  Contains primarily keratinocytes and melanocytes, Langerhans cells = primarily in this layer, compose ~5% of all cells in epidermis