Factors involved in the 'rotation' of the human embryonic stomach around its longitudinal axis: computer-assisted morphometric analysis

The majority of studies as to whether gastric and nongastric factors are in volved in the 'rotation' of the human embryonic stomach around its longitud inal axis have been morphological. The aim of this study was to analyse, wi th morphometric support, the influence on the angular modifications during gastric rotation of the simultaneous changes of the gastric walls and mesen teric growth, and the volumes of organs adjacent to the stomach (right, lef t and posterior groups). Computer imaging techniques were applied on cross sections of a graded series of 10 human embryos (from Carnegie stage (CS) 1 1) and 2 fetuses. A clockwise gastric rotation occurred during the embryoni c period. The most rapid angular modifications took place from CS 11 to 16, after the rotation became oscillatory with angular changes in clockwise an d anticlockwise directions, reaching the highest value at CS 18 (at the sup raomental part of the stomach: 54.37 degrees; at the omental part: 68.03 de grees); after this period the angular values tended to stabilise. The predo minant growth of the left gastric wall over the right and the changes in th e width of the gastric mesentery were the most persistent factors involved in the modifications of the transverse gastric angle during the embryonic p eriod although without relationship to their direction. During the increasi ng angular phases, clockwise rotation was promoted by the decrease of the v olume of any group of organs adjacent to the stomach. When the volume of th e left and posterior groups increased simultaneously, clockwise or anticloc kwise angular directional change was related to the respective decrease or increase adjacent organ volume to the right. We conclude that the stomach o f the human embryo undergoes heterogeneous and multifactorial rotation as a consequence of the overall increase in gastric wall growth to the left and the increase of gastric mobility produced by the previous mesenteric enlar gement, and that the rotational direction results from the forces exerted o n the stomach and the gastric mesenteries by the adjacent organs.