Top Ten Powerful Nations 2013 (According to Global Presence). Top Ten Powerful Countries Ranking (2012). NOTE: National Power Index (NPI) 2012 is a comprehensively revised version of the previous National Security Indexes published in Indiaâs National Security Annual Review (INSAR) series since 2002.op Ten Powerful Nations 2013 (According to Global Presence). Top Ten Powerful Countries Ranking (2012). NOTE: National Power Index (NPI) 2012 is a comprehensively revised version of the previous National Security Indexes published in Indiaâs National Security Annual Review (INSAR) series since 2002.
Overview. When you take in food, it's the job of your digestive tract to break that food down into smaller pieces through mechanical digestion, and then break larger molecules into smaller ones through chemical digestion.
In chemical digestion, enzymes break down food into the small molecules the body can use. In the human digestive system, food enters the mouth and mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact of saliva.n chemical digestion, enzymes break down food into the small molecules the body can use. In the human digestive system, food enters the mouth and mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact of saliva.