1. The rigid vessels are called arteries which originate from the heart and supply blood to various organs in the body.
2. The largest artery is the aorta which arises from the left ventricle supplies oxygenated blood to all parts of the body except lungs.
3. The relatively smaller one is pulmonary artery supplies deoxygenated blood to lungs.
4. A pair of coronary arteries carry oxygenated blood to the muscles of heart.