Lesser sac and foramen of Winslow - Applied anatomy of stomach part 2
The lesser sac, also known as the omental bursa, is a cavity in the abdomen that lies behind the stomach and the lesser omentum, between the posterior wall of the stomach and the anterior surface of the pancreas. It is part of the peritoneal cavity and is formed by the folding of the peritoneum, which is the serous membrane lining the abdominal cavity.
The boundaries of the lesser sac are formed by several important structures:
- Anteriorly: It is bounded by the stomach, the lesser omentum (which includes the hepatogastric and hepatoduodenal ligaments), and the gastrocolic ligament.
- Posteriorly: The lesser sac is bordered by the pancreas, the left kidney and adrenal gland, and the splenorenal ligament.
- Superiorly: It is limited by the diaphragm and the caudate lobe of the liver.
- Inferiorly: The transverse mesocolon and the transverse colon form the lower boundary.
- Laterally: The spleen, the gastrosplenic ligament, and the splenorenal ligament are located on the left side, while the right side is continuous with the greater sac via the foramen of Winslow (epiploic foramen).
The lesser sac allows the stomach to move freely against the structures behind it during peristalsis and other movements. It communicates with the greater sac (the main part of the peritoneal cavity) through the foramen of Winslow.
Foramen of Winslow (Epiploic Foramen)
The foramen of Winslow, also known as the epiploic foramen, is a crucial anatomical passage that connects the lesser sac to the greater sac of the peritoneal cavity. It is located posterior to the free edge of the lesser omentum, which contains the portal triad (the hepatic artery, portal vein, and bile duct).
The foramen of Winslow is bounded by:
- Anteriorly: The hepatoduodenal ligament, which contains the portal triad.
- Posteriorly: The inferior vena cava and the adrenal gland.
- Superiorly: The caudate lobe of the liver.
- Inferiorly: The first part of the duodenum and the horizontal part of the common hepatic artery.
This small opening plays an essential role in surgical procedures, particularly in cases of internal herniation or when accessing the structures within the lesser sac. Understanding its precise anatomical relationships is crucial for surgeons to avoid complications during abdominal surgeries. The foramen is large enough to allow communication between the greater and lesser sacs but small enough to be a potential site for the entrapment of bowel loops, leading to internal hernias.