Integumentary system

• Integumentary system


  Body's outer covering

  
• Integumentary system


  • Supports
  • Protects
  • Regulates body temperature
  • Performs receptor functions
• Components of the integumentary system

  • Skin
  • Hairs
  • Nails
  • Glands

  
• Skin


  Largest external organ of the body
• Main layers of the skin

  • Epidermis
  • Dermis
  • Hypodermis (subcutaneous)

  
• Epidermis


  • No blood vessels
  • Functions: protection, waterproofing, hair and nails, skin color

  
• Layers of the epidermis

  • Stratum corneum
  • Stratum lucidum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale

  
• Stratum corneum


  Uppermost multi-layer of dead, keratinized, cornified squamous cells
• Keratin


  Waterproofing protein
• Stratum corneum


  Continuously sheds off
• Stratum lucidum


  Only found in thick skin, provides additional thickness to these areas

  
• Stratum granulosum


  Has active keratinocytes - cells producing keratin
• Stratum spinosum


  Mostly consists of keratinocytes held together by sticky proteins called desmosomes
• Stratum basale


  Lowermost layer, one layer of columnar or cuboidal cells, mitosis layer (cells are actively dividing), melanocytes - melanin, responsible for skin pigment

  
• Melanin


  Higher melanin production results in darker skin color, lower melanin production results in lighter skin color, acts as protection against harmful UV rays by scattering UV rays, eumelanin is more photoprotective than pheomelanin
• Vitamin D synthesis


  1. UVB exposure

  2. Cholecalciferol (D3)

  3. Calcidiol

  4. Calcitriol (active form)

  5. Absorption of calcium and phosphorus

  
• Dermis


  Second layer of the skin, acts as the skin glue, functions: elasticity, nourishes epidermis, sensory stimulation, fingerprint & footprint

  
• Structures in the dermis

  • Areolar connective tissue
  • Blood vessels
  • Sensory receptors
  • Follicles
• Areolar connective tissue in dermis

  Elastin fibers provide elasticity, collagen fibers provide structure and tensile strength

  
• Blood vessels in dermis

  Veins, arteries, and skin capillaries, provide nourishment to skin cells, thermoregulatory functions
• Sensory receptors in dermis

  • Mechanoreceptors (physical deformation)
  • Thermoreceptors (heat and cold)
  • Pain receptors or nociceptors (harmful conditions)
• Hypodermis


  Lowermost layer of the skin, made up of fats and adipose tissue, functions: high energy reserves, insulation, cushion, body contour

  
• Hair


  • Produced by the basale cells of the skin, made up of keratin protein and cuticle, no hair in palm and soles, has two main parts: hair root and hair shaft
• Functions of hair


  • Thermoregulation
  • Protection
  • Sensation
• Nails


  • Thin, hard covering at the fingertips and toes, made up of cuticle and keratin, functions: protect toes and fingers, grasping small objects, defensive structures (claws), has two main parts: nail body/plate and nail root
• Nail clubbing


  Associated with chronic low blood oxygen levels
• Types of glands


  • Sebaceous glands
  • Sudoriferous (sweat) glands
• Sebaceous glands

  Sac-like exocrine gland whose duct opens into the hair, secrete oil or sebum to lubricate the hair and contribute to skin acidity, Meibomian glands are found in the eyelids
• Types of sweat glands

  • Eccrine sweat glands
  • Apocrine sweat glands
• Eccrine sweat glands


  Found almost everywhere, secretion is composed of water, NaCl, urea, uric acid, and potassium, function in thermoregulation and minor excretion
• Apocrine sweat glands


  Found in armpit and ano-genital area, secretion is mainly water, proteins, and amino acids, active during puberty, emotional stress, and sexual stimulation, cause body odor
• Modified sweat glands


  • Ceruminous glands (secrete earwax)
  • Ciliary glands (produce tear-like substance to lubricate the eyes)
  • Mammary glands (secrete milk to provide nourishment to an infant)
• Effects of aging on the skin: rough and dry, benign tumors and lesions, discoloration, slack or soggy, loses fat, transparent and fragile, easily bruised, gray hair
• Skin care