Dorsal Mesogastrium: Anatomy, Derivatives, and Function

The dorsal mesogastrium is an embryonic structure composed of a double layer of peritoneum, the membrane lining the abdominal cavity. It functions to suspend the primitive stomach from the posterior wall of the abdomen. This structure is temporary but foundational, as it develops into several permanent anatomical features in the adult abdomen.

Origin and Early Development

The dorsal mesogastrium originates from the splanchnic mesoderm, a layer of embryonic tissue that gives rise to the connective tissues of the gut. In the early embryo, the primitive gut tube is suspended by a continuous sheet of this tissue called the dorsal mesentery. The portion of this mesentery that attaches to the developing stomach is the dorsal mesogastrium, which is initially a simple, straight structure holding the stomach in place.

This arrangement changes as the stomach undergoes a complex rotation. The stomach rotates 90 degrees clockwise on its longitudinal axis, causing what was the posterior surface to face right and the anterior surface to face left. This rotation pulls the dorsal mesogastrium to the left, creating a new space behind the stomach called the omental bursa, or lesser sac.

The dorsal mesogastrium then elongates downward, growing more rapidly than the surrounding structures and creating a large, apron-like fold. It is within this developing fold that another organ, the spleen, begins to form. The spleen’s development is tied to this mesentery, which serves as a conduit for its blood supply.

Transformation into Adult Structures

The elongated and folded dorsal mesogastrium transforms into several distinct structures in the adult abdomen. The most prominent of these is the greater omentum. This large, apron-like sheet hangs down from the greater curvature of the stomach, drapes over the small intestines, and then folds back up to attach to the transverse colon. This structure is formed from the fusion of the two layers of the elongated dorsal mesogastrium.

The formation of the spleen within the dorsal mesogastrium creates two important ligaments. The portion of the dorsal mesogastrium that connects the stomach to the spleen becomes the gastrosplenic ligament. The part that connects the spleen to the posterior abdominal wall, near the left kidney, develops into the splenorenal ligament. These ligaments serve as pathways for blood vessels.

These derived structures establish the final anatomical relationships of the upper abdomen. The greater omentum lies anterior to most of the intestines, while the gastrosplenic and splenorenal ligaments secure the spleen in its position in the upper left quadrant of the abdomen. These complex folding events turn a temporary support structure into permanent, functional components.

Essential Functions and Roles

During embryonic life, the primary role of the dorsal mesogastrium is to suspend the stomach and provide a scaffold for developing organs. It acts as a highway for arteries, such as branches of the celiac trunk, to reach the stomach and spleen. This ensures these developing organs receive the necessary blood supply. Nerves and lymphatic vessels also travel within this mesenteric sheet.

In the adult, the derivatives of the dorsal mesogastrium have new functions. The greater omentum is a dynamic organ with roles in fat storage and immunity. It contains a large number of immune cells, particularly macrophages, which has earned it the nickname “the policeman of the abdomen.” It can migrate to sites of inflammation or infection, helping to wall off the area.

The ligamentous derivatives also have specific functional roles. The gastrosplenic ligament carries the short gastric arteries and the left gastro-omental vessels to the stomach. Similarly, the splenorenal ligament serves as a conduit for the splenic artery and vein, the primary vessels supplying and draining the spleen.

Associated Medical Conditions

Abnormalities in the development of the dorsal mesogastrium can lead to several medical conditions. One such condition is gastric volvulus, a rare event where the stomach twists on itself. This twisting can obstruct the stomach and compromise its blood supply, and it is sometimes associated with excessive laxity or abnormal formation of the anchoring ligaments.

The derivatives of the dorsal mesogastrium can also be the site of pathologies. Cysts or tumors can arise in the greater omentum, requiring surgical intervention. Because of its rich blood supply and lymphatic drainage, the omentum can also become a site for the metastatic spread of cancers from organs like the ovaries and stomach.

An understanding of the anatomy derived from the dorsal mesogastrium is important for surgeons. During procedures like a gastrectomy or a splenectomy, the surgeon must dissect the gastrosplenic and splenorenal ligaments. Identifying and ligating the blood vessels that run through these structures is a required part of these operations to prevent bleeding.