Assertion: vein's layer | /r/HasProperty | thick outer
Facets:
Source sentences:
text: Microscopically, veins have a thick outer layer made of connective tissue, called the tunica externa or tunica adventitia.
text: Veins have a thick outer layer made of collagen and below this are thin bands of smooth muscle and elastic tissue, with the innermost layer being made up of endothelium cells.