The most important system in the human body is gastrointestinal (GI) system which comprises of gastrointestinal tract and accessory organs. The gastrointestinal tract is a long hollow tube that stretches from the oral cavity (where food enters) and goes through esophagus, stomach, small and large intestine, rectum and finally opening into anus from where undigested food carried off. The accessory organs are salivary glands, liver and pancreas secreting enzymes into digestive tract for food digestion. Another important part of GI system is gall bladder which stores bile.The most significant function of digestive system is that it processes different nutrients and energy from the food and fluids that a human body ingests. In order to perform this function, the GI system breaks down the food components into the simplest form. Carbohydrates, proteins, fat, vitamins, minerals and fiber are the major components of food. Water is also a component of food. During the process of digestion, the components of carbohydrates, starch and sugars found in bread, pasts, potatoes etc. break down into glucose and fructose. Similarly, components of fat, found in meat, cheese, butter etc. break down into fatty acids and cholesterol. Components of proteins, found in eggs and fish break down into amino acids.