General Facts

General facts about skin :
  • Skin is the largest organ in the body, accounting for 15-20% of total body weight & covers a surface area of 2 m2.
  • Human skin consists of 3 main layers;
    1. upper epidermis
    2. middle dermis &
    3. lower sub-cutaneous tissue
  • The epidermis is mainly composed of keratinocytes and is 0.4-1.5mm in thickness. It is formed by division of cells in the basal layer which move outwards forming upper layers. The cellular progression from the basal layer to the skin surface takes about 30 days.
  • Melanocytes are cells that distribute packages of melanin pigment which gives skin its colour. It is the nature of the melanin and the size of the cells containing it rather than the number of melanocyte that account for the different appearances between white and black skin.
  • The dermis is a supporting matrix with a remarkable capacity for retaining water. The thickness of the dermis varies from less than 0.5 mm to more than 5 mm. There are two principal types of protein, collagen and elastic tissue, out of which collagen comprises 80–85% of the dry weight.
  • Skin also contains many supporting structures like hair follicles, pilosebaseous unit which secrete oily substance called sebum

  • Functions of skin:
    1. The main function of skin is to act as a barrier to external environment which can be
      • Permeability barrier to water
      • Barrier to bacteria & other micro-organisms
      • Mechanical barrier
      • Barrier to ultraviolet rays
  • Regulation of body temperature achieved through dilation or constriction of blood vessels or secretion of sweat by sweat glands
  • As sensory organ, helping in perception of different sensations
  • Subcutaneous fat has important role in cushioning trauma as well as providing insulation and a calorie reserve.
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