Arteries are blood vessels leading away from the heart. With the exception of the pulmonary arteries, they carry oxygenated blood. As a rule they have a relatively thick wall rich in muscular tissue. Arteries have to withstand the pressure caused by the heart pumping blood into the circulation. This means that after each contraction of the heart, a surge of pressure can be felt in the arteries. This is known as the pulse. In the horse the pulse can be felt on the lower jaw just in front of the cheek (A. facialis) and on the inside and outside of the fetlock (Aa. digitales palmares/plantares). The main artery carrying blood from the heart into the systemic circulation is known as the aorta.