An experimental analysis of shoulder and lateral body wall development in the chick embryo

Abstract

AbstractDevelopment of the shoulder and a change in the axis of outgrowth of the wing in the chick embryo have been shown to be accompanied by morphogenetic movements in the lateral body wall adjacent to the base of the wing. The manner in which the cells moved was studied by grafting labeled mesoderm into unlabeled hosts and by periodic photographs of carbon particles placed in live embryos. Histological techniques were used to determine the final location of the markers, and maps were constructed of the cell movements. It was observed that cells in the lateral body wall cranial to the wing and overlying the pleural coelom moved caudally to form the base of the shoulder. This movement occurred between stage 23 and stage 27. Starting at stage 25, the cells in the lateral body wall caudal to the wing moved ventrally and then cranially to form the sternum and connective tissue of the ventro‐medial thoracic body wall; this movement was complete by stage 31. As a result of these two morphogenetic movements, cells in the proximal portion of the wing were also displaced. The net effect is formation of the shoulder, while the base of the wing rotates ventrally with respect to the somites.