Pancreas in embryogenesis

Human pancreas is formed by its ventral and dorsal buds from ending of the 4th week of embryogenesis. The smaller ventral bud rotates about a ductal segment of midgut under influence intensive growing bud of the liver, its prevailing right part, in process of uneven growth of walls of a ductal segment of midgut with prevalence its left semi-circumference. In morphogenesis of dorsal pancreatic bud, it may distinguish the caudal sag under influence of stomach, which moves caudally under pressure of a left part of the liver. In result whole pancreatic anlage acquires winding, S-figure form. State of the pancreas in the embryo of the beginning of 7th week corresponds its angle and L-figure shapes after birth. It is gradual straightening and “ascending” of the pancreas, particularly its tail, in abdominal cavity on 8th and 9th weeks of embryogenesis. Pancreas acquires the shape of a plate, obliquely situating and widening in caput. Thus it is described stretching or tongue-formed the shape of the definitive pancreas. Different morphogenesis of this organ put first of all in touch with different sizes of the liver relatively abdominal cavity. Usually, development of definitive pancreatic ducts regards as part of the process of merging of pancreatic buds. It is set on finishing stage of this process. But at first, the (future main pancreatic) duct of ventral pancreatic bud units with bile duct during 5th and beginning of 6th weeks, which liver “stretches” from narrowing right semi-circumference of a ductal segment of the midgut. Thickening layers of differential connective tissue “draw" epithelial pancreatic tubules rather quickly from ending of 6th week - beginning of the 7th week of embryogenesis with connection with an accumulation of hyaluronan and proteoglycans, the formation of more and thicker network of more and thicker reticular fibres. Branching growth of epithelium of pancreatic buds makes it possible around the epithelial intestinal tube, and dense packing of small branches of pancreatic endodermal buds increases, probably, of their penetrating force during growth in dense mesenchyme.