K.C.S.E Biology Q & A - MODEL 2013PP2QN08

K.C.S.E Biology Q & A - MODEL 2013PP2QN08

 Describe the role of the following organs in excretion and homeostasis.
(a) the liver 
(b) the skin during hot environmental conditions. 

ANSWERS

​(a) Regulation of blood sugar ; when blood sugar is below normal/90 mg/100 cm3 glucagon ; triggers the conversion of glycogen to glucose in the liver ; the glucose is released into the blood stream. When blood sugar is in excess above normal/10 mg/100cm3, insulin; causes the liver to convert glucose excess to glycogen ; which is stored.
Production of heat energy ; by increasing the rate of metabolic activities: Excretion of bile pigments ; produced due to breakdown of worn out red blood cells: Deamination/removal of amino group of excess amino acids to form urea: and detoxication/poisonous/toxic substances:
(b) Sweat glands excrete urea; excess water; and salts: hence maintaining salt & water balance in the blood. Evaporation of sweat; cools the body due to loss of latent heat of vaporization; when the body temperature rises : blood vessels in the skin vasolidate: allowing more blood to flow near the skin surface: thus heat is lost to the environment radiation/convection. The eretor pili mucle relaxes hair flattens ; in a hot environment reducing insulation: hence heat is lost from the body by radiation! convection; to the environment.