An artery is an elastic blood vessel that transports blood away from the heart. There are two main types of arteries: pulmonary arteries and systemic arteries.

Pulmonary arteries carry blood from the heart to the lungs where the blood picks up oxygen. The oxygen rich blood is then returned to the heart via the pulmonary veins. Systemic arteries deliver blood to the rest of the body. The aorta is the main systemic artery and the largest artery of the body. It originates from the heart and branches out into smaller arteries which supply blood to the head region (brachiocephalic artery), the heart itself (coronary arteries), and the lower regions of the body.

The smallest arteries are called arterioles and they play a vital role in microcirculation. Microcirculation deals with the circulation of blood from arterioles to capillaries to venules (the smallest veins). The liver, spleen and bone marrow contain vessel structures called sinusoids instead of capillaries. In these structures blood flows from arterioles to sinusoids to venules.