Skin

• How much percent does skin account for in the adult humans total body weight ?

  15%
• Skin is the outermost covering of the body. It is stretched all over in the form of a layer.
• protection is the primary function of the skin it efforts protection in four different ways

  (I) protects underlying tissue from mechanical shocks

  (Ii) it holds the body fluids inside and prevent excess loss of water by evaporation (iii) it prevents harmful substances or disease causing germs from entering our body (iv) protects the body against excess ultraviolet light which is potentially very harmful
• What are the other functions of the skin besides protection?

  1)Temperature regulation, 2)sensation, 3)storage of food, 4)excretion 5)vitamin D synthesis and (6)grip [puckered skin gives a better grip in slippery wet environment]
• Skin proper

  •epidermis - cornified , granular and germinative layers

  •dermis - elastic fibres, blood vessels, nerves
• Derivatives of the skin

  •hair •nails •mammary glands •sweat glands •sebaceous glands
• Epidermis


  The outer thinner part of the skin which is formed of stratified epithelium piled up layer after layer. Thick and hard on the palms soles and heels. It is devoid of blood vessels
• Three regions of the epidermis

  (a) outermost cornified layer

  (b) middle granular layer

  (c) inner malpighian layer
• (a) the cornified layer (stratum corneum) is the outermost layer consisting of


  Several piled up layers of flattened dead cells which are made of a fibrous structural protein called keratin.
• How do the cells of stratum corneum get replaced?

  Its cells are continually worn away or shed and are replaced from beneath by those arising from the deeper malpighian layer
• Importance of stratum corneum

  The cornified layer is tough and offers resistance to three things:

  (I) mechanical damage

  (Ii) bacterial infection

  (Iii) loss of water by evaporation
• The granular layer

  A very thin middle lager consisting of two or three sub layers of flattened cells.
• The malpighian layer

  The malpighian layer or stratum malpighian or germinative layer is the innermost region of the epidermis

  Its cells can't actively divide to produce new cells which press and shift outward to replace the worn out cells if the outermost cornified layer.
• How is our skin colour determined?

  By the amount and type of melanin, a pigment, contained in the cells of the malpighian layer produced in our skin.
• Leukoderma (vitiligo) symptoms

  Skin pigmentation melanin is lost from smaller or larger patches at different regions of the body; however the exact cause is not yet known.
• Albinism symptoms

  Complete loss of pigmentation all over the skin

  The skin of affected individuals appears pinkish because of the underlying blood capillaries

  Albinism is a recessive trait caused due to inheritance
• What is the dermis made of?

  Inner thick layer of connective tissue made of elastic fibre which is tough and flexible.