Round Ligament Of The Liver

Omental bursa

Gastrolienal ligament

Figure 13.10 A. The positions of the spleen, stomach, and pancreas at the end of the fifth week. Note the position of the spleen and pancreas in the dorsal mesogastrium. B. Position of spleen and stomach at the 11th week. Note formation of the omental bursa or lesser peritoneal sac.

Pancreas

Lienorenal Ligament

Liver

Lesser omentum Falciform ligament

Lienorenal ligament

Liver

Adrenal gland

Dorsal mesogastrium Spleen

Omental bursa Stomach

Lesser omentum Falciform ligament

Pancreas

Lienorenal ligament

Round Ligament Liver

Parietal peritoneum of body wall

Spleen Gastrolienal ligament

Parietal peritoneum of body wall

Spleen Gastrolienal ligament

Figure 13.11 Transverse sections through the region of the stomach, liver, and spleen, showing formation of the lesser peritoneal sac, rotation of the stomach, and position of the spleen and tail of the pancreas between the two leaves of the dorsal mesogastrium. With further development, the pancreas assumes a retroperitoneal position.

13.11). Lengthening and fusion of the dorsal mesogastrium to the posterior body wall also determine the final position of the pancreas. Initially the organ grows into the dorsal mesoduodenum, but eventually its tail extends into the dorsal mesogastrium (Fig. 13.10A). Since this portion of the dorsal meso-gastrium fuses with the dorsal body wall, the tail of the pancreas lies against

Mesogastrium

Figure 13.12 A. Derivatives of the dorsal mesentery at the end of the third month. The dorsal mesogastrium bulges out on the left side of the stomach, where it forms part of the border of the omental bursa. B. The greater omentum hangs down from the greater curvature of the stomach in front of the transverse colon.

Figure 13.12 A. Derivatives of the dorsal mesentery at the end of the third month. The dorsal mesogastrium bulges out on the left side of the stomach, where it forms part of the border of the omental bursa. B. The greater omentum hangs down from the greater curvature of the stomach in front of the transverse colon.

this region (Fig. 13.11). Once the posterior leaf of the dorsal mesogastrium and the peritoneum of the posterior body wall degenerate along the line of fusion, the tail of the pancreas is covered by peritoneum on its anterior surface only and therefore lies in a retroperitoneal position. (Organs, such as the pancreas, that are originally covered by peritoneum, but later fuse with the posterior body wall to become retroperitoneal, are said to be secondarily retroperitoneal.)

As a result of rotation of the stomach about its anteroposterior axis, the dorsal mesogastrium bulges down (Fig. 13.12). It continues to grow down and forms a double-layered sac extending over the transverse colon and small intestinal loops like an apron (Fig. 13.13 A). This double-leafed apron is the greater omentum; later its layers fuse to form a single sheet hanging from the greater curvature of the stomach (Fig. 13.13 B). The posterior layer of the greater omentum also fuses with the mesentery of the transverse colon (Fig. 13.13B).

The lesser omentum and falciform ligament form from the ventral meso-gastrium, which itself is derived from mesoderm of the septum transversum. When liver cords grow into the septum, it thins to form (a) the peritoneum of the liver, (b) the falciform ligament, extending from the liver to the ventral body wall, and (c) the lesser omentum, extending from the stomach and upper duodenum to the liver (Figs. 13.14 and 13.15). The free margin of the falciform ligament contains the umbilical vein (Fig. 13.10A), which is obliterated after birth to form the round ligament of the liver (ligamentum teres hepatis). The free margin of the lesser omentum connecting the duodenum and liver (hep-atoduodenal ligament) contains the bile duct, portal vein, and hepatic artery (portal triad). This free margin also forms the roof of the epiploic foramen of

Stomach

Omental bursa

Greater omentum

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