Our topic for today is Digestive System in Humans. Digestion is a process in which complex food material is broken down into simpler substances. The digestion of food in humans takes place in the alimentary canal, which is a long tube extending from the mouth to the anus. The different parts of the alimentary canal are buccal cavity, food pipe or oesophagus, stomach, small intestine, large intestine and anus. Two glands namely, liver and pancreas also help in digestion. The food is taken in through the mouth. It is chewed and mixed with saliva in the buccal cavity. Saliva is a digestive juice secreted by the salivary glands. The chewed food enters into the food pipe or oesophagus and is then slowly pushed into a bag like structure called stomach. The food is churned in the stomach to further break it down. The stomach also secretes mucous, digestive juices and hydrochloric acid. The hydrochloric acid kills the bacteria in the food and makes the food acidic. The food then goes into a highly coiled tube called small intestine. The small intestine receives secretions from the liver and pancreas. The liver secretes bile juice while the pancreas secretes pancreatic juice. The walls of the small intestine also secrete juices, which help in further digestion of food. The inner surface of the small intestine has finger like projections called villi. The villi have extensive network of blood vessels. The digested food is then passed into the blood vessels . The undigested food is passed into the large intestine. It is wider than the small intestine. Excess of water and salts are absorbed here and undigested waste is passed out of the body through the anus.