Digestion in the Small Intestine

 The duodenum is the first part of the small intestine. The middle and last sections of the small intestine are the jejunum and ileum respectively.

    Several substances are secreted into the duodenum. The pancreas secretes pancreatic juice, a watery alkaline liquid containing several digestive enzymes. The liver produces blue which is stored in the gall bladder. Bile is a greenish alkaline liquid which does not contain digestive enzymes. When chyme enters the duodenum, certain hormones stimulate and pancreas and gall bladder to send their digestive juices to the duodenum.

    Pancreatic juice contains three important enzymes. Amylopsin breaks down starch to maltose. Trypsin, a protease, breaks down proteins fats to carboxylic acids and glycerol. all the enzymes of the pancreatic juice require an alkaline medium to work in.

    Although bile does not contain digestive enzymes, it is Important for digestion. It contains a high percentage of water and therefore adds water to chyme. Secondly, its alkaline (sodium) salts neutralize the hydrochloric acid in chyme and allows the enzymes of the pancreatic juice to begin working. Thirdly bile reduces the surface tension of fats and emulsifies them. This means that large fat and oil drops are broken down into tiny droplets, thus providing a larger surface area for enzyme action.

      During its passage Through the duodenum, the chyme's more watery and is called chyle. In the ileum, intestinal juice is produced by special cells of the small intestine. This liquid contains a number of enzymes which work in alkaline medium and complete the process of digestion. Maltose is changed to glucose by maltose. Lactose is changed to glucose to galactose by lactase. Sucrose is changed to glucose and fructose by sucrase and fructose by sucrase. The end products of carbohydrate digestion are thud simple sugars (glucose , fructose and galactose). In the case of proteins, erepsin changes all polypeptides to amino acids which are the end products of protein digestion. Lipase changes fats to carboxylic acids and glycerol.