The duodenum is the first of the three parts of the small intestine that receives partially digested food from the stomach and begins with the absorption of nutrients. The duodenum is directly attached to the pylorus of the stomach.
The duodenum (Latin word for 12, so named for being 12 finger breadths in length) is a C-shaped, approximately 25-30cm long tubular organ, located at the level of 1st-3rd lumbar vertebrae.
The organ begins at the pylorus on the right and it has 4 parts that wrap around the head of the pancreas and ends at the duodenojejunal flexure/junction at approximately level of 2nd Lumbar vertebrae, 2-3cm to the left of the midline.
The duodenum has four parts:
The superior part of the duodenum lies intraperitoneally and is enlarged proximally. The enlargement is called the duodenal bulb. It is connected to the liver by the hepatoduodenal ligament and ends at the superior duodenal. It then becomes the descending part. The superior part of duodenum lies anterolateral to the body of the first lumbar vertebra.
The Descending part goes inferior to the lower border of the vertebral body of the 3rd Lumbar vertebra. It then makes a sharp turn medially into the inferior duodenal flexure, the end of the descending part. It then becomes the horizontal part.
The descending duodenum has an important clinical relevance because of the pancreatic duct and common bile duct that enter the descending duodenum, through the major duodenal papilla. The descending part of the duodenum also contains the minor duodenal papilla where the accessory pancreatic duct enters the duodenum.
The Horizontal part runs cranially along the left side of the vertebral column from right to left ventrally from the abdominal aorta and inferior vena cava. The ascending part of duodenum joins the jejunum at the duodenojejunal flexure.
The duodenum is attached to the back of the abdominal wall through the suspensory ligament of the duodenum (also known as the ligament of Treitz) which is the theoretical border between the upper and lower gastrointestinal tract.