Integumentary system

• Integumentary system


  Composed of the skin, hair, oil and sweat glands, nails, and sensory receptors
• Skin


  • Consists of 2 main parts: the superficial, thinner epidermis and the deeper, thicker dermis
• Epidermis


  Composed of keratinized stratified squamous epithelium containing keratinocytes, melanocytes, Langerhans cells, and Merkel cells
• Epidermis


  • Keratinocytes produce keratin and form a barrier to prevent moisture loss and entry of foreign substances
  • Melanocytes produce melanin to protect skin from sun damage
  • Langerhans cells participate in immune responses
  • Merkel cells detect touch sensations
• Lamellar granules


  Release lipid-rich secretion that acts as a water-repellent sealant
• Keratinization


  As cells move from stratum basale to stratum corneum, they accumulate more keratin
• Epidermal layers


  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum corneum
• Thick skin


  Has an additional layer called stratum lucidum
• Dermis


  Composed mainly of connective tissue containing collagen and elastic fibers
• Layers of dermis


  • Papillary layer
  • Reticular layer
• Papillary layer


  • Contains areolar connective tissue, dermal papillae with touch receptors (Meissner corpuscles), capillary loops, and sensory neurons
• Meissner corpuscle


  A type of touch receptor located in the dermal papillae
• Reticular layer


  • Contains dense irregular connective tissue with bundles of collagen and elastic fibers, as well as adipose cells, hair follicles, nerves, oil glands, and sweat glands
• Skin pigments


  Melanin, hemoglobin, and carotene
• Accessory structures of the skin

  • Hair
  • Glands
  • Nails
• Hair


  • Consists of a shaft, root, and bulb (follicle)
  • Associated with arrector pili muscles and sebaceous glands
• Sebaceous glands


  Produce sebum to moisturize hair and waterproof the skin
• Skin glands


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


  Secrete cerumen (earwax) to protect the ear canal
• Sudoriferous glands


  • Apocrine sweat glands
  • Eccrine (merocrine) sweat glands
• Nails


  Hard, dead, keratinized epidermal cells covering the terminal portions of the fingers and toes
• Parts of a nail

  • Nail body
  • Free edge
  • Nail root
  • Lunula
  • Cuticle
  • Nail matrix
• Nail matrix


  Proximal portion of the epithelium deep to the nail root where cell division produces new nails
• Functions of the skin

  • Body temperature regulation
  • Protection
  • Cutaneous sensations
  • Vitamin D synthesis
  • Excretion and absorption
• Parts of the nail

  • Nail body
  • Free edge
  • Nail root
  • Lunula
  • Cuticle
  • Nail matrix
• Nail matrix


  The proximal portion of the epithelium deep to the nail root
• Cell division of the matrix cells

  Produces new nails
• Functions of the skin

  • Body temperature regulation
  • Protection
  • Cutaneous sensations
  • Excretion and absorption
  • Synthesis of vitamin D
• Body temperature regulation


  • Skin contributes to homeostatic regulation of body temperature by liberating sweat at its surface and by adjusting the flow of blood in the dermis
• Protection


  • Keratin in the skin protects underlying tissues from microbes, abrasion, heat, and chemicals
  • Lipids released by lamellar granules inhibit evaporation of water from the skin surface
• Strenuous physical activities


  • Skiing
  • Running
• During strenuous physical activities

  Dermal blood vessels dilate and sweat secretion increases
• In response to low temperatures

  Dermal blood vessels constrict to minimize heat loss
• Cutaneous sensations


  • Tactile sensations (touch, pressure, vibration, and tickling)
  • Thermal sensations (warmth and coolness)
  • Pain
• Excretion and absorption


  The skin has a small ability to absorb and excrete chemicals and toxins
• Synthesis of vitamin D


  Exposing skin to UV radiation activates vitamin D which ultimately aids in dietary calcium and phosphorus absorption in the intestines
• Merkel receptor


  Disk-shaped receptor located near the border between the epidermis and dermis, detecting steady pressure from small objects
• Meissner corpuscle


  Stack of flattened cells located in the dermis, near the epidermis; detecting texture or movement of objects against the skin
• Ruffini cylinder


  Located in the dermis and has many branched fibres inside a cylindrical capsule; detecting steady pressure or stretching, such as during the movement of a joint
• Pacinian corpuscle


  Layered, onion-like capsule surrounding a nerve fibre, located deep in the dermis, in the subcutaneous fat; detecting large changes in the environment, such as vibrations