Duodenum

Duodenum

The duodenum is the first section of the small intestine in most higher vertebrates, including humans. It is a hollow jointed tube connecting the stomach to the jejunum.

Anatomy

Diagram of the duodenum and surrounding structures.

The duodenum is approximately 25–30 cm (10–12 inches) long and is shaped like a "C". It is divided into four parts:

1. The superior part
2. The descending part
3. The horizontal part
4. The ascending part

The duodenum is located in the upper abdomen and is mostly retroperitoneal, meaning it is located behind the peritoneum.

Histology

Histological section of the duodenum showing the villi.

The duodenum has a unique histological structure that includes:

• Villi: Finger-like projections that increase the surface area for absorption.
• Microvilli: Microscopic projections on the surface of the villi.
• Brunner's glands: Located in the submucosa, these glands secrete an alkaline mucus that helps neutralize gastric acid.

Microvilli of the duodenum under a microscope.

Function

The primary function of the duodenum is to receive the chyme from the stomach and continue the process of digestion. It also plays a crucial role in:

• Neutralizing stomach acid
• Mixing chyme with digestive juices from the pancreas and bile from the liver
• Absorbing nutrients such as iron and calcium

Clinical Significance

Duodenum with amyloid deposition.

The duodenum can be affected by various diseases and conditions, including:

• Duodenal ulcer: A common form of peptic ulcer disease.
• Celiac disease: An autoimmune disorder affecting the small intestine.
• Giardiasis: An infection caused by the parasite Giardia lamblia.

Duodenum affected by giardiasis.

Development

The duodenum develops from the foregut and midgut during embryogenesis. It is initially a solid cord of cells that later becomes a hollow tube.

Related Pages

• Small intestine
• Jejunum
• Ileum
• Stomach
• Pancreas

Gallery

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  Diagram showing the position of the duodenum in the digestive system.
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  Anatomy of the small intestine, including the duodenum.
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  Illustration of the duodenum and its relation to surrounding organs.