Veins are the ones that transport blood from the body into the heart and are characterized because transport blood poor in oxygen and transport carbon dioxide as well as other cellular debris, they are composed of three layers and a thin layer of smooth muscle. So the sentences are as follows
1)Wide lumen (there is no blank space)
2) Thin inner wall (in general all the wall is thin but is divided into three parts being the inner, tunic intima the thinnest)
3) smooth muscle tissue in the walls (the inner layer is composed of endothelial cells, middle smooth muscle, and outer connective tissue)
4) Valves to control blood flow