Lower Extremity Venous Duplex Here is a short video covering anatomy, protocol and some pointers on color doppler optimization. Veins are blood vessels that carry deoxygenated blood toward the heart (with the exception of the pulmonary and portal veins which carry oxygen rich blood to the left atrium and liver respectively). Veins and arteries are made up of the same 3 layers tunica intima: Inner most layers comprised of enothelial cells tunica media: middle layer comprised of smooth muscle tuni