DUODENUM

Duodenum

The duodenum is a portion of the small intestine that receives bile and pancreatic juice from the bile and pancreatic ducts. It is the first part of the small intestine and has a C-shaped structure.

Location

• The duodenum is located between the stomach and the jejunum.
• It is situated behind the peritoneum in the abdominal cavity.

Boundaries

• The duodenum is bounded by the:
  • Pancreas (superiorly)
  • Liver (superiorly)
  • Transverse colon (inferiorly)
  • Ascending colon (inferiorly)

Lymphatic Drainage

• The lymphatic vessels from the duodenum drain into the pancreaticoduodenal nodes.
• The lymphatic vessels from the pancreaticoduodenal nodes drain into the superior mesenteric lymph nodes.
• The lymphatic vessels from the superior mesenteric lymph nodes drain into the paraaortic lymph nodes.

Blood Supply

• The blood supply to the duodenum is provided by the:
  • Superior pancreaticoduodenal artery (from the gastroduodenal artery)
  • Inferior pancreaticoduodenal artery (from the superior mesenteric artery)
  • Right gastroepiploic artery (from the gastroduodenal artery)
  • Superior mesenteric artery (from the aorta)
  • Inferior pancreaticoduodenal artery (from the superior mesenteric artery)

Nerve Supply

• The nerve supply to the duodenum is provided by the:
  • Vagus nerve (from the cranial nerves)
  • The vagus nerve sends fibers to the duodenum through the celiac ganglia.
  • The celiac ganglia sends fibers to the duodenum through the pancreaticoduodenal nerves.
  • The pancreaticoduodenal nerves are formed by the fibers from the vagus nerve and the sympathetic nerves from the celiac ganglia.

Muscle Action Sequence

• The muscle action sequence in the duodenum is as follows:
  • Step 1 → The smooth muscle cells in the duodenal wall contract to mix food with digestive enzymes.
  • Step 2 → The contraction of the smooth muscle cells in the duodenal wall pushes the food into the jejunum.
  • Step 3 → The food is then mixed with digestive enzymes in the jejunum.

Functions

• The duodenum is responsible for:
  • Absorption of nutrients from the food
  • Neutralization of gastric acid by the bile and pancreatic juice
  • Mixing of food with digestive enzymes Duodenum (MSØV)

1. Describe the morphology of duodenum

• Duodenum is a C-shaped, narrow, and long part of the small intestine, approximately 25 cm in length and 2.5 cm in diameter.
• It is the first segment of the small intestine, situated between the pylorus of the stomach and the jejunum.
• The duodenum is divided into four regions: superior, descending, horizontal, and ascending parts.

2. Describe interior of duodenum

• The interior of the duodenum is lined with mucous membrane, which is composed of intestinal epithelial cells and lamina propria.
• The duodenum contains longitudinal and circular layers of smooth muscle.
• The mucous membrane is folded into longitudinal ridges called valvulae conniventes, which increase the surface area for absorption.

3. Describe the blood and nerve supply of duodenum

• The blood supply of the duodenum is provided by the superior pancreaticoduodenal artery (from the gastroduodenal artery) and the inferior pancreaticoduodenal artery (from the superior mesenteric artery).
• The nerve supply of the duodenum is provided by the vagus nerve (via the vagal branches) and the sympathetic plexus (from the celiac plexus).
• The superior mesenteric plexus also supplies the duodenum.

4. Describe the applied anatomy

• The duodenum is related to the following structures:
  • Right crus of the diaphragm
  • First part of the duodenum is close to the gallbladder and the bile duct
  • Second part of the duodenum is related to the head of the pancreas
  • Third part of the duodenum is related to the body of the pancreas and the superior mesenteric artery
  • Fourth part of the duodenum is related to the transverse colon and the ascending colon