A) GIVE THE FUNCTIONS OF THE SKIN IN ORGANISMS. (6 MKS) B) HOW IS THE MAMMALIAN SKIN MODIFIED TO ENABLE IT PERFORM ITS FUNCTIONS? (14MKS)

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 a) Give the functions of the skin in organisms. (6mks) 

  • It protects the underlying tissues against mechanical injury, UV-light rays and entry of pathogens; (Rej. germs) 
  • As an excretory organs, it enables organisms to eliminate excess water, ions and traces of urea; 
  • As an sensory organ, it enables the organisms to be aware of deviations in pressure, touch and 
  • temperature from the external environment; 
  • It is a thermoregulator such that it enables the body to lose excess heat to lower its temperature back to norm or may enable the organisms to store its heat if the temperature is lower and hence raise it back to the norm; 
  • It takes part in osmoregulation by enabling the body fluids to get rid of excess water or excess ions; 
  • It takes part in the regulation of the pH of body fluids by enabling the body to get rid of either Hydrogen ions or bicarbonate ions; 

(b) How is the mammalian skin modified to enable it perform its functions? (l4mks)

  • Presence of the cornified layer; which is tough and has keratin to enable it protect the underlying tissues  from mechanical injury; 
  • It also has sebum; which is antiseptic and enables it to protect the body against entry of pathogens. 
  • Presence of melanin; enables it to protect the underlying tissues against 
  • damage by UV-light radiations. 
  • It has sweat glands with secretory cells; which absorb excess water, excess ions and traces of urea from blood and secrete them into the sweat duct; 
  • Has the sweat pores; which open on the skin surface to allow for elimination of sweat containing excess water, excess ions and traces of urea;  
  • It has nerve endings; which enables it to detect any deviations in temperature, pressure and contact/touch; 
  • It has hair follicles; which stand erect when temperature is lower than normal to reduce heat loss from the body or lie flat to enable to body lose excess heat and lower temperature back to the norm when the internal temperature is higher; 
  • Has blood vessels; which vasodilate when temperature is higher than norm to enable the organisms lose heat; the blood vessels vasoconstrict when the temperature is lower than the norm to reduce heat loss from the body;

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