What happens in the duodenum?

The duodenum is the first segment of the small intestine. It is an important segment as it receives both pancreatic juice and bile. Pancreatic juice comes from the pancreas and contains several digestive enzymes.

Pancreatic amylase continues to transform complex carbohydrates, such as starch and glycogen. These are mainly transformed into glucose and maltose.

Pepsin starts the transformation of protein in the stomach. Several enzymes in the duodenum, including trypsin and chymotrypsin, continue to transform proteins. These enzymes break down the short chains of amino acids into small peptides and amino acids.

Lipases are enzymes that transform lipids into fatty acids and glycerol.

Bile emulsifies lipids, forming tiny droplets of fat that facilitate the action of these lipases. An emulsion is a mixture of two liquids that do not normally mix, such as water and oil. Bile comes from the liver. It is yellowish in colour and is stored in the gall bladder.

How are nutrients absorbed?

Peristaltic waves help nutrients travel through the small intestine. These are the same type of contractions as those found in the oesophagus and stomach.

By the time nutrients reach the small intestine, they have been sufficiently transformed to be able to pass through the intestinal wall and be absorbed. The small intestine is lined with millions of folds called villi. These folds increase the absorption surface.

Nutrients then pass into the blood vessels, which take them to all the body’s cells to help them perform their specific functions.