9 Duodenum

Small Intestine

After food exits the stomach it enters the hose-like organ known as the small intestine. The small intestine which is directly distal of the stomach separated with pyloric sphincter can be divided into 3 sections each with their unique features and histology: the duodenum, jejunum, and ileum. The small intestine is paramount in absorption of nutrients through finger-like projections on the border of the small intestine called villi. In fact each villi is covered in even smaller finger like projections known as microvilli:

Duodenum

Lets start with the first segment known as the C-shaped duodenum which is roughly the first 25-40cm of the small intestine responsible for receiving the stomach’s content and integrating several digestive enzymes.

The duodenum has several identifiable characteristics. For instance, the plicae circulares are folds within the lumen(interior) of the duodenum which increase the surface area for absorption and mixing.

With regards to the function of the duodenum, it first receives chyme from the stomach and mixes in several digestive enzymes from the pancreas, liver and gallbladder. These enzymes flow from the duodenal papilla to break down big food particles into delicious nutrients.

The duodenum is also laced with Brunner’s glands which secrete bicarbonate rich mucus to help diffuse the acidic chyme from the stomach. This very basic (opposite of acidic) acts like a fire extinguisher so the rest of the small intestine is not corroded by the acidic chyme.