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Learning objectives

After completing this study unit you will be able to:

  1. Identify the four parts of the duodenum and the landmarks which define their boundaries.
  2. Name the main functions of the duodenum.
  3. Understand the internal structure of the duodenum.
  4. Appreciate the anatomical relations of the duodenum.

Watch video

The duodenum is the first segment of the small intestine, extending from the pyloric sphincter of the stomach to the jejunum. It can be divided into the superior, descending, horizontal and ascending parts. Only the proximal section of the superior part is intraperitoneal, and thus the most mobile, while the rest of the duodenum is retroperitoneal. Its functions are to dilute and neutralize digestive juices, digest and process chyme passed on from the stomach, receive pancreatic enzymes and bile, as well as absorb various nutrients. The wall of the duodenum consists of three main layers: an inner mucosa with defined circular folds (of Kerckring), an underlying submucosa and a double layered muscular coat.

Take a detailed look at the duodenum and the structures related to it in the video below.

Take a quiz

Now that you have finished the video on the duodenum, test what you’ve learned with the quiz below! Identify the structures in the video with the identification questions, or really get stuck in with our exam questions.

If you want more of a challenge, take this custom quiz on the small intestine! Fine tune it by choosing topics or individual terms that you want to be tested on.

Browse atlas

Explore parts of the duodenum one by one in this atlas gallery.

Now turn your attention to the anatomical relations of the duodenum.


Key points about the duodenum
Parts Superior: from pyloric sphincter to superior duodenal flexure
from superior duodenal flexure to inferior duodenal flexure
from inferior duodenal flexure to ascending part
from horizontal part to the duodenojejunal flexure
Internal structure Mucosa (with circular folds (of Kerckring))
Muscular coat (outer longitudinal, inner circular layers)
Openings Major duodenal papilla - from hepatopancreatic ampulla
Minor duodenal papilla - from accessory pancreatic duct
Ligaments Hepatoduodenal ligament (part of lesser omentum)
Suspensory muscle of duodenum (ligament of Treitz)
Relations In curve of duodenum - head of pancreas
Posterior - abdominal aorta, hepatic portal vein, inferior vena cava, gastroduodenal artery, bile duct, right kidney, ureter and psoas major, L3 vertebra, right gonadal vessels
Anterior - superior mesenteric artery/vein, gallbladder, right lobe of liver

Well done!

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