What is Digestion?
'''Digestion''' is the [[process]] of breaking down food to [[absorption|absorb]] it. Food is broken down into smaller pieces, which are [[soluble]] in water. Only then can the food be absorbed into the [[bloodstream]]. Digestion happens in three phases. Mechanical digestion is the physical breakdown of large pieces of food into smaller pieces, which are made by digestive [[enzymes]]. In chemical digestion, enzymes break down food into the small [[molecules]] the body can use. Finally, the [[nutrients]] are absorbed into the [[blood stream]]. Once in the blood stream, the nutrients are taken to the [[liver]], which is a kind of chemical factory for the body. After we swallow food, it travels down a muscular tube to the [[stomach]]. There, it is mashed into soupy [[fluid]] called [[:en:Chyme|chyme]]. The mixture passes into the [[small intestine]], where tiny bits of food pass into the bloodstream. The food that is still left goes into the [[large intestine]]. Finally, waste products leave the body. Digestion usually takes about 18 hours. Food stays in the stomach for about three hours.<ref name=firste>{{cite book |last=Morris |first=Neil |author2=Ting Morris |others=Branka Surla, Rosie Alexander |title=Children's First Encyclopedia |editor=Jim Miles, Lynne French |publisher=Miles Kelly Publishing, Bardfield, Essex |date=1998 |isbn=1-84084-332-2 }} Accessed 13 July 2010.</ref> If uncoiled, the small intestine would be about six [[meter]]s (20 [[feet]]) long.<ref name=firstbody>{{cite book |title=My First Book on the Human Body |publisher=Robert Frederick Ltd |location= Bath |date=2004 |isbn=0-7554-3506-0 }} Accessed 13 July 2010.</ref> Many digestive tracts are about as long as a [[bus]].<ref name=firstbody/> Food slowly enters the [[small intestine]] from the stomach. This is where [[nutrient]]s are taken into the [[blood]]. It then enters the [[large intestine]]. [[Water]] is taken away from it. The food that is left is called [[feces]]. The feces are stored in the [[rectum]] until the waste can leave the bo