DUODENAL X-RAY. DUODENAL X-RAY The duodenum is the initial segment of the small intestine, extending from the pylorus to the jejunum. Measuring approximately 25 centimeters, it is composed of 4 parts. The first part is called the duodenal bulb. The second part receives secretions from the gall bladder and pancreas. The third and fiurth parts are horizontal and ascending. The duodenum plays an essential role in digestion since it absorbs calcium, vitamins, iron, and lipids.