Artery and vein the the forestomach of a goat.

The artery is on the right and has a thick muscular tunica media. The vein is on the left is thin walled and partially collapsed.

 

The thick walled artery is on the right. Note the endothelium (hardly visible except for the round nuclei that are bulging into the lumen) and the internal elastic lamina (the refractile squiggly line directly underneath the endothelium). The tunica media is much thicker than that of the vein on the left and is much larger than the tunica externa. The vein on the left has a tunica media that is only about a couple of smooth muscle cells thick. The lumina contains mostly red blood cells with some white blood cells and proteinaceous precipitate.