Question

Why do we call a pulmonary vein as a vein and a pulmonary artery as an artery?

Answer 1

The concept of calling a vein a vein and an artery an artey is basically their entry and exit from heart. A blood vessel going to heart is a vein and going out of heart is an artery. So even though pulmonary artery carries deoxygenated or as we call it impure blood, unlike all other arteries which carry oxygenated/pure blood, it is called an artery, because it takes blood from heart to lungs. So is the case for pulmonary vein.