Anatomy of Duodenum

Study Notes

Duodenum Structure

The duodenum is divided into four parts: superior, descending, inferior, and ascending.
The superior (first) part lies at the level of L1 vertebra.
The descending (second) part lies at the level of L1-L3 vertebrae.
The inferior (third) part lies at the level of L3 vertebra.
The ascending (fourth) part begins at the left of L3 and ascends to L2 vertebra.

Relations of Each Part of the Duodenum

Superior (First) Part

Anteriorly: Relations with the quadrate lobe of the liver and the gallbladder.
Posteriorly: Relations with the lesser sac, gastroduodenal artery, bile duct, portal vein, and inferior vena cava.
Superiorly: Relations with the entrance into the lesser sac (epiploic foramen).
Inferiorly: Relations with the head of the pancreas.

Descending (Second) Part

Anteriorly: Relations with the gallbladder (fundus) and transverse colon.
Medially: Relations with the head of the pancreas, bile duct, and pancreatic ducts.
Relations with the minor duodenal papilla (if present).

Inferior (Third) Part

Anteriorly: Relations with the root of the mesentery of the small intestine and superior mesenteric vessels.
Posteriorly: Relations with the right ureter, right psoas muscle, inferior vena cava, and aorta.
Superiorly: Relations with the head of the pancreas.
Inferiorly: Relations with coils of jejunum.

Ascending (Fourth) Part

Anteriorly: Relations with the beginning of the root of the mesentery and coils of jejunum.
Posteriorly: Relations with the left psoas major and sympathetic chain.
Superiorly: Relations with the uncinate process of the pancreas.
Left margin: Relations with the aorta.

Blood Supply and Lymphatic Drainage

The upper half of the duodenum is supplied by the superior pancreaticoduodenal artery, a branch of the gastroduodenal artery.
The lower half of the duodenum is supplied by the inferior pancreaticoduodenal artery, a branch of the superior mesenteric artery.
The superior pancreaticoduodenal vein drains into the portal vein.
The inferior vein joins the superior mesenteric vein.
Lymph vessels follow the arteries, draining upward via pancreaticoduodenal nodes to the gastroduodenal nodes to the celiac nodes, and draining downward via pancreaticoduodenal nodes to the superior mesenteric nodes.

Nerve Supply

The nerves are derived from sympathetic and parasympathetic (vagus) nerves from the celiac and superior mesenteric plexuses.

Clinical Correlation

Duodenal Ulcer: An ulcer of the anterior wall of the first inch of the duodenum may perforate into the upper part of the greater sac, above the transverse colon.

Description

Learn about the parts and structure of the duodenum, including its location, boundaries, and division into four parts. Understand the relationships with surrounding structures like the pylorus, jejunum, and omentum.