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==Introduction==

==Introduction==

The duodenum is the proximal part of the small intestine and extends from the pylorus of the [[Forestomach - Anatomy & Physiology|stomach]] to the [[Jejunum - Anatomy & Physiology|jejunum]]. It has descending and ascending portions and both portions have digestive and absorptive functions.

The duodenum is the proximal part of the small intestine and extends from the pylorus of the [[Monogastric Stomach - Anatomy & Physiology|stomach]] to the [[Jejunum - Anatomy & Physiology|jejunum]]. It has descending and ascending portions and both portions have digestive and absorptive functions.

==Structure==

==Structure==

*The descending duodenum passes out of the pylorus of the [[Forestomach - Anatomy & Physiology|stomach]] (on the right side of the abdomen) and has a sigmoid flexure. It passes towards the right abdominal wall and rises dorsally. In its passage it is related dorsally to the right lobe of the [[Pancreas - Anatomy & Physiology|pancreas]], ventrally to the [[Jejunum - Anatomy & Physiology|jejunum]] and medially to the ascending [[Colon - Anatomy & Physiology|colon]] and [[Caecum - Anatomy & Physiology|caecum]].  

*The descending duodenum passes out of the pylorus of the [[Monogastric Stomach - Anatomy & Physiology|stomach]] (on the right side of the abdomen) and has a sigmoid flexure. It passes towards the right abdominal wall and rises dorsally. In its passage it is related dorsally to the right lobe of the [[Pancreas - Anatomy & Physiology|pancreas]], ventrally to the [[Jejunum - Anatomy & Physiology|jejunum]] and medially to the ascending [[Colon - Anatomy & Physiology|colon]] and [[Caecum - Anatomy & Physiology|caecum]].  

**At a point between the right [[Macroscopic Renal Anatomy - Anatomy & Physiology#Common Anatomy|kidney]] and pelvic inlet it turns medially and cranially around the root of the mesentery to become the ascending duodenum. The point of turn is called the ''caudal flexure'' of the duodenum.

**At a point between the right [[Macroscopic Renal Anatomy - Anatomy & Physiology#Common Anatomy|kidney]] and pelvic inlet it turns medially and cranially around the root of the mesentery to become the ascending duodenum. The point of turn is called the ''caudal flexure'' of the duodenum.

**The ascending duodenum is shorter and bends ventrally to enter the mesentery and becomes the [[Jejunum - Anatomy & Physiology|jejunum]].

**The ascending duodenum is shorter and bends ventrally to enter the mesentery and becomes the [[Jejunum - Anatomy & Physiology|jejunum]].

**The bile duct and one of the pancreatic ducts discharge into the proximal part of the duodenum by separate ''major duodenal papillae''.

**The bile duct and one of the pancreatic ducts discharge into the proximal part of the duodenum by separate ''major duodenal papillae''.

**The second pancreatic duct discharges a little more distally on a smaller papilla.

**The second pancreatic duct discharges a little more distally on a smaller papilla.

*The cranial part of the descending duodenum is attached to the [[Liver - Anatomy & Physiology|liver]] by the '''hepatoduodenal ligament'''. This is a remnant of the [[Forestomach - Anatomy & Physiology|ventral mesogastrium]] in the embryo.

*The cranial part of the descending duodenum is attached to the [[Liver - Anatomy & Physiology|liver]] by the '''hepatoduodenal ligament'''. This is a remnant of the [[Monogastric Stomach - Anatomy & Physiology|ventral mesogastrium]] in the embryo.

**The bile duct runs within the hepatoduodenal ligament.

**The bile duct runs within the hepatoduodenal ligament.