Before the growth of the great omentum is pronounced the continuity of the mesoduodenum and dorsal mesogastrium can be readily appreciated (Fig. 218). But after the redundant growth of the membrane has carried the great omentum further caudad, the stomach and the two omental layers attached to the greater curvature lie in front of the structures included between the two dorsal layers and conceal them from view (Fig. 177). [Illustration: FIG. 218.--Schematic view of primitive mesentery after intestinal rotation and incipient formation of omental bursa from dorsal mesogastrium.] In sagittal sections to the left of the median line (Figs. 221 and 222) the pancreas now appears included between the layers of the great omentum near their point of departure from the vertebral column. (This point is of course identical with the prevertebral attachment of the primitive dorsal mesogastrium from which the omentum is developed.) [Illustration: FIGS. 221, 222.--Schematic sagittal sections through stomach, pancreas, great omentum, and left kidney.] [Illustration: FIG. 221.--Before adhesion between dorsal and mesogastrium and parietal peritoneum.] [Illustration: FIG. 222.--After adhesion.] The foregoing considerations will, therefore, lead to the conclusion that the pancreas presents, in regard to its peritoneal relations, two distinct segments: 1. The portion adjacent to duodenum (head and neck of the gland) is developed between the layers of the mesoduodenum. 2. The distal portion of the gland, comprising the body and tail, develops between the layers of the great omentum (dorsal segment), derived from the primitive dorsal mesogastrium. The transections of the dorsal mesogastrium shown in Figs. 180 and 181 will now have to be amplified by the introduction of the body of the pancreas between the two layers of the vertebro-splenic segment, in addition to the splenic artery (Figs. 219 and 220). [Illustration: FIGS. 219, 220.--Schematic transection of dorsal mesogastrium, pancreas, spleen, and stomach.] [Illustration: FIG. 219.--Before adhesion to primitive parietal peritoneum (arrow indicates the direction in which the adhesion takes place).] [Illustration: FIG. 220.--After adhesion and formation of secondary line of transition between mesogastrium and parietal peritoneum (lieno-renal ligament).] Hence the following facts will be understood: 1. In the adult the splenic artery supplies a series of small branches to the pancreas as it courses along the cephalic border of the gland on its way to the spleen. 2. After the above-described adhesion of the original left leaf of the dorsal mesogastrium (vertebro-splenic segment) to the parietal peritoneum (Fig. 220), the dorsal surface of the body of the pancreas loses its peritoneal investment and becomes attached by connective tissue to the ventral surface of the left kidney.