How is duodenum anatomy?

Duodenum is the first part of small intestine. It is C – shaped structure. It is only 25 cm long. It is retroperitoneal and fixed to posterior abdominal wall. It Begins at pylorus and ends at the ligament of Treitz. It becomes jejunum opposite the second lumbar vertebra. Duodenum is divided into four portions: First or Superior part . Second or Descending part . Third or Horizontal part . Fourth or Ascending part