The first segment of the small intestine is:

Explanation

Option A is correct. The first segment of the small intestine is the duodenum. The small intestine is a long, coiled tube that is divided into three parts: the duodenum, the jejunum, and the ileum. The duodenum is the shortest and widest part of the small intestine. It is about 10 inches long and curves around the head of the pancreas. The duodenum is responsible for the initial digestion of food. It receives food from the stomach and mixes it with digestive juices from the pancreas and liver. The digestive juices in the duodenum break down carbohydrates, proteins, and fats into smaller molecules that can be absorbed into the bloodstream. The other options are not the first segment of the small intestine: The jejunum is the second segment of the small intestine. It is about 16 feet long and is located between the duodenum and the ileum. The jejunum is responsible for the absorption of most of the nutrients from food. The ileum is the third and longest segment of the small intestine. It is about 20 feet long and is located between the jejunum and the colon. The ileum is responsible for the absorption of the remaining nutrients from food, as well as the absorption of bile salts and water. The colon is the large intestine. It is about 5 feet long and is located between the ileum and the rectum. The colon is responsible for the absorption of water and the storage of waste products.