1)Medium-sizedA 内弹性膜 -muscular 平滑肌 中膜一 Tunica intima endothelium subendothelial layer: CT:4-2A ask 外弹性膜 营养血 collagenous F 指肪细胞 elastic F smooth muscle internal elastic membrane wave-liked pink-colored band- elastin1) Medium-sized A – muscular A ---Tunica intima endothelium subendothelial layer: CT -collagenous F -elastic F -smooth muscle internal elastic membrane: wave-liked, pink-colored band- elastin