Describe the structure and function of the mammalian skin.

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   It  has  a  cornified  layer  made  up  of  dead  cells  and  is  tough  and  impermeable  to  water;  to  protect the  skin  against  mechanical  damage;  bacterial  infections  and  water  loss;  granular  layer;  whose cells  divide  to  form  the  cornified  layer;  malpighian  layer;  which  is  made  up  of  diving  cells  that give  rise  to  a  new  granular  layer;  contains  melanin;  to  protect  skin  against  ultra-violet rays/radiations;  Sebaceous  glands;  which  secrete  sebum;  to  make  the  skin  supple/soft  and waterproof;  sebum  is  also  antiseptic;  Blood  vessels;  dilate  during  hot  weather;  increasing  blood flow  near  the  skin  surface;  heat  loss  is  enhanced;  constrict;  in  cold  weather;  less  blood  flow; minimize  heat  loss;  Sensory  nerve  endings  and  receptors;  enable  detection  of  external environmental  changes;  Highly  coiled  sweat  glands;  secrete  sweat;  to  control  body temperature;  when  hot  sweat  evaporates  cooling  the  body;  sweat  contains  excretory  products; subcutaneous  fat/adipose  tissue  in  dermis;  for  insulation;  hair;  to  regulate  body  temperature;  in cold  weather  erector  pili  muscles  contract;  hair  is  raised,  air  trapped  to  insulate  the  body;  in  hot weather,  erector  pili  muscles  relax;  hair  lies  flat  reducing  insulation;  dense  network  of  blood capillaries;  supply  nutrients/oxygen  to  skin  tissues;  as  well  as  carrying  away  wastes  and  carbon (IV)  oxide  away  from  the  skin  tissues;  adipose  tissue/sub-cutaneous  layer;  serves  as  an insulator;  helping  in  temperature  control;  helps  in  manufacture  of  vitamin  D;  Max.  20  mks

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