Distinct morphological changes in the proximal portions of the chick DA during development.

Representative histological sections of the proximal and distal DA from ED16 to AB. Serial sections were stained with HE (a) and EVG staining (b). (a) The nucleus in the middle lamella of the distal DA were aligned in parallel to the internal elastic laminar and layered throughout the hatching, whereas the layers were disorganized in the proximal DA from the IP stage. Scale bars are 50 μm. (b) The proximal DA and the distal DA had a muscular and an elastic type of artery, respectively. Moreover, in the proximal DA, the poor elastic fiber formation was observed in the middle lamella from the IP stage. Scale bars are 50 μm. (c) The vessel wall thickness of the chick DA at developmental stages. The vessel wall of the proximal DA was thin compared to the distal DA at the ED16 and ED19 stage. Moreover, the vessel wall of the proximal DA drastically thickened from the ED19 to the IP stage. * and ** indicate p ppp pp ppp < 0.05. n = 4–5.