Duodenum

<p>The duodenum is the first section of the <a href="/facts/Small_intestine/1AQ8RJ4m">small intestine</a> in most <a href="/facts/Vertebrates/tT54FSTT">vertebrates</a>, including <a href="/facts/Mammals/phSwTzBo">mammals</a>, <a href="/facts/Reptiles/04n1uKf1">reptiles</a>, and <a href="/facts/Birds/RJF6zwLP">birds</a>. In mammals, it may be the principal site for <a href="/facts/Iron/QK1JYy8E">iron</a> absorption.
The duodenum precedes the <a href="/facts/Jejunum/PU0q1Syr">jejunum</a> and <a href="/facts/Ileum/rCWGkFuf">ileum</a> and is the shortest part of the small intestine.
</p><p>In humans, the duodenum is a hollow jointed tube about 25–38 centimetres (10–15 inches) long connecting the <a href="/facts/Stomach/Q4PPDGT6">stomach</a> to the jejunum, the middle part of the small intestine. It begins with the <a href="/facts/Duodenal_bulb/S9lUT625">duodenal bulb</a>, and ends at the <a href="/facts/Duodenojejunal_flexure/YzQvGeh8">duodenojejunal flexure</a> marked by the  <a href="/facts/Suspensory_muscle_of_duodenum/HwgHgkCR">suspensory muscle of duodenum</a>. The duodenum can be divided into four parts: the first (superior), the second (descending), the third (transverse) and the fourth (ascending) parts.
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Duodenum open-in-new

Duodenum