Henry Gray (18251861). Anatomy of the Human Body. 1918.
of the duodenum a short distance above the hepatic diverticulum, and, growing upward and backward into the dorsal mesogastrium, forms a part of the head and uncinate process and the whole of the body and tail of the pancreas. The ventral part appears in the form of a diverticulum from the primitive bile-duct and forms the remainder of the head and uncinate process of the pancreas. The duct of the dorsal part (accessory pancreatic duct) therefore opens independently into the duodenum, while that of the ventral part (pancreatic duct) opens with the common bile-duct. About the sixth week the two parts of the pancreas meet and fuse and a communication is established between their ducts. After this has occurred the terminal part of the accessory duct, i. e., the part between the duodenum and the point of meeting of the two ducts, undergoes little or no enlargement, while the pancreatic duct increases in size and forms the main duct of the gland. The opening of the accessory duct into the duodenum is sometimes obliterated, and even when it remains patent it is probable that the whole of the pancreatic secretion is conveyed through the pancreatic duct.
FIG. 1102 Pancreas of a human embryo at end of sixth week. (Kollmann.) (See enlarged image)
FIG. 1103 Schematic and enlarged cross-section through the body of a human embryo in the region of the mesogastrium. Beginning of third month. (Toldt.) (See enlarged image)
At first the pancreas is directed upward and backward between the two layers of the dorsal mesogastrium, which give to it a complete peritoneal investment, and its surfaces look to the right and left. With the change in the position of the stomach the dorsal mesogastrium is drawn downward and to the left, and the right side of the pancreas is directed backward and the left forward (Fig. 1103). The right surface becomes applied to the posterior abdominal wall, and the peritoneum which covered it undergoes absorption (Fig. 1104); and thus, in the adult, the gland appears to lie behind the peritoneal cavity.
Structure (Fig. 1105).In structure, the pancreas resembles the salivary glands. It differs from them, however, in certain particulars, and is looser and softer in its texture. It is not enclosed in a distinct capsule, but is surrounded by areolar tissue, which dips into its interior,