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1. Development of the Stomach Stomach develops from distal part of foregut. It is initially a simple tubular midline structure Around the middle of the fourth week, a slight dilation indicates the site of the future stomach It first appears as a fusiform enlargement of the caudal part of the foregut. This primordium soon enlarges and broadens dorsally. This is due to differential growth on dorsal side. During the next 2 weeks the dorsal border of the primitive stomach grows faster than its ventral border; this demarcates the greater curvature of the stomach

2. Rotation of the developing stomach . During development the developing stomach rotates along two axes. These rotations determine the final position of stomach in left hypochondrium . First Rotation 90 degress clockwise deffrential growth Orignal left side becomes ventral surface orignal right side becomes dorsal surfaces

3. Second rotation - Anterior posterior axis Before rotation the cranial and caudal ends of the stomach are the median plane After roation the stomach assumes its final position its long axis almost transverse to the long axis of the body

4. Mesenteries of the stomach The stomach is suspended from the dorsal wall of the abdominal cavity by a dorsal mesentery called dorsal mesogastrium . This mesentery is originally very thick and lies in the median plane. Later on it is shifted to left side due to rotation of stomach A ventral mesentery called ventral mesogastrium attaches the stomach with anterior abdominal wall. It is in fact septum transversum .

5. Later on as the stomach rotates along longitudinal axis , dorsal mesogastrium is carried to the left therebys enlarging the bursa. Now there is a large recess of thes peritoneal cavity behind stomach. The omental bursa expands transversely and cranially and soon lies between the stomach and the posterior abdominal wall. This pouch like bursa (L., purse) facilitates movements of the stomach). At this stage, omental bursa is related anteriorly to stomach and posteriorly to posterior abdominal wall. Its left lateral boundary is dorsal mesogastrium . It is wide open on to the right side.

6. The primordium of spleen appears in 5th week of development as a mesodermal proliferation between the two leaves of dorsal mesogastrium . As the omental bursa expands and swings to the left side, a portion of dorsal mesogastrium behind spleen fuses with the peritoneum of posterior abdominal wall . The fused layers are absorbed and disappear . Thus the tail of pancreas become retroperitoneal Remember that pancreas develops idirorsal mesoduodenum , but later on its tail expands its dorsal mesogastrium

7. • Spleen maintains its intraperitoneal position, • It is connected with dorsal body wall in the region of left kidney by lienorenal ligament (Lien L., spleen) and to stomach by gastrosplenic ligament. • These two ligaments are nothing but parts of dorsal mesogastrium .

8. Later on as stomach enlarges and rotates around anterio -posterior axis the dorsal mesogastrium forming the left wall of omental bursa is thrown downward. It grows enormously downward forming anterior and posterior layers of dorsal mesogastrium in front of transverse colon and small intestinal loops like an apron. Anterior layer is hanging down from greater curvature of stomach and posterior layer from posterior abdominal wall. The space between the two layers is called inferior recess of omental bursa,

9. • Later on these anterior and posterior layers fuse to form a single sheet hanging downward from greater curvature of stomach. • The posterior layer also fuses with the mesentery of transverse colon. • The fused apron of dorsal mesogastrium hanging downward from greater curvature of stomach is now called greater omentum (L., fat skin ). • This is a four-layered membrane. It overhangs the developing intestines. • The inferior recess of omental bursa disappears as the anterior and posterior layers of greater omentum fuse.

10. Ventral mesogastrium is actually septum transversum . It is between foregut and anterior abdominal wall. Later on the liver bud enters in septum transversum and the liver grows within septum transversum . As a result of the enormous growth of liver, the mesenchyme of septum transversum becomes stretched and membranous thus forming Falciform ligament, between anterior abdominal wall and liver The peritoneal coving forming the false capsule of liver and lesser omentum between liver and stomach/upper part of duodenum.

11. The free margin of falciform ligament contains umbilical vein, which after birth is obliterated to form ligamentum teres hepatic. Lesser omentum between liver and stomach isAcalled hepato -gastric ligament, while the part of lesser omentum between liver and duodenum is hepato -duodenal ligament . The free marging of lesser omentum between liver and duodenum contains bile duct,portal vein and hepatic artery. In adults h right border of lesser omentum forms the anterior boundary of epiploic foramen.epiploic foramne is the connction betwn lesser sac and greater sac

12. Liver is completely covered by peritoneum forming the false capsule of liver. Ilt is derived from the mesenchyme of septum transversum Superiorly a triangular portion of liver is not covered by peritoneum. This triangular area is called the bare area of liver. It is covered by diaphragm. Here liver is attached to diaphragm by areolar tissue Remember that diaphragm also develops from septum transversum