Structure and Functions of the Skin

• What are the three distinct layers of the skin?

  The epidermis, dermis, and hypodermis
• What is the primary function of the integumentary system?

  To provide overall protection to the body
• What type of cells mainly make up the epidermis?

  Keratinocyte cells
• What is keratin and its role in the skin?

  Keratin is a fibrous protein that provides hardness and water-resistant properties
• How thick is the epidermal layer?

  Around a tenth of a millimeter thick
• What does it mean that the epidermis is avascular?

  It does not contain any blood vessels
• What are the four separate layers of the epidermis?

  The stratum basale, stratum spinosum, stratum granulosum, and stratum corneum
• What is keratinisation?

  It is a process of differentiation where keratinocytes produce keratin
• What happens to keratinocytes during their transition through the epidermis?

  They undergo several changes to their structure and composition
• What is the role of filaggrin in keratinocytes?

  Filaggrin breaks down to form natural moisturizing factor
• What are corneocytes?

  Flat, anucleate cells in the stratum corneum containing keratin
• How does the stratum corneum protect against water loss?

  It provides a water impermeable barrier
• How does the structural arrangement of the stratum corneum resemble a brick wall?

  Keratinocytes are the bricks held together by intercellular lipids as mortar
• What is trans-epidermal water loss?

  It is the daily loss of water through the skin
• What is the additional fifth layer of the epidermis called?

  The stratum lucidum
• Where is the stratum lucidum found?

  In areas of thick skin such as palms and soles
• What do melanocytes produce?

  The pigment melanin
• What are the two forms of melanin?

  Pheomelanin (red to yellow) and eumelanin (dark brown to black)
• What is the role of Langerhans cells?

  They act as antigen presenting cells in the immune response
• What do Merkel cells function as?

  Mechanoreceptors allowing the sense of touch
• What does the dermis contain?

  Blood vessels, sensory nerves, and lymphatic vessels
• What are the two layers of the dermis?

  The papillary layer and the reticular layer
• What is the primary component of the reticular layer of the dermis?

  Collagen
• What is the role of collagen in the skin?

  It provides tensile strength to the dermis
• What percentage of the dry weight of the skin does collagen account for?

  Approximately 80%
• How does aging affect collagen production?

  Collagen production declines with age
• What is the role of elastin in the skin?

  It provides resilience and suppleness
• What are glycosaminoglycans (GAGs)?

  Polysaccharides that attract water and create the ground substance
• What is assessed to determine skin hydration?

  Skin turgor
• What do fibroblasts synthesize?

  Collagen, elastin, and glycosaminoglycans
• What do mast cells contain?

  Histamine, prostaglandins, and leukotrienes
• What is the role of macrophages in the dermis?

  They engulf bacteria and assist in tissue homeostasis and repair
• What is the function of the subcutaneous layer?

  It acts as a shock absorber and heat insulator
• What are the main functions of the skin?

  1. Protection against water loss
  2. Prevention of entry of infective agents and chemicals
  3. Regulation of body temperature
  4. Protection against the effects of UV radiation
• What do antimicrobial peptides (AMPs) do?

  They inactivate and kill invading microorganisms
• What is the role of keratinocytes in tissue healing?

  They self-regulate their proliferation and differentiation
• How does the skin regulate body temperature?

  By dilating or constricting blood vessels and producing sweat
• What is the composition of sweat?

  Predominantly water, but also contains sodium, urea, lactic acid, and potassium
• What happens to blood flow to the skin when the atmospheric temperature decreases?

  Blood flow to the skin reduces
• What causes the characteristic body odor from apocrine sweat glands?

  Breakdown of secretions by surface bacteria