Arteries: Arteries Carry Away The heart pumps blood out through
one main artery called the dorsal aorta. The main artery then
divides and branches out into many smaller arteries so that each
region of your body has its own system of arteries supplying it
with fresh, oxygen-rich blood. Arteries are tough on the outside
and smooth on the inside. An artery actually has three layers:
an outer layer of tissue, a muscular middle, and an inner layer
of epithelial cells. The muscle in the middle is elastic and
very strong. The inner layer is very smooth so that the blood
can flow easily with no obstacles in its path. The muscular wall
of the artery helps the heart pump the blood. When the heart
beats, the artery expands as it fills with blood. When the heart
relaxes, the artery contracts, exerting a force that is strong
enough to push the blood along. This rhythm between the heart
and the artery results in an efficient circulation system. You
can actually feel your artery expand and contract. Since the
artery keeps p