Blood Vessels Blood flow through the circulatory system in blood vessels:
Arteries are large vessels that carry blood away from the heart to the
tissues of the body. Except for the pulmonary arteries, all arteries carry oxygen-
rich blood.
Carillaries are the smallest vessels. Their thin walls allow oxygen and
nutrient to pass from blood into tissues and wastes to move from tissues into
blood.
Veins return blood to the heart. Many have valves that
prevent backflow. the concration of the heart produce a wave of fluid pressure in
the arteries,known as blood pressure. Without that pressure, blood would stop
flowing through the body. The body regulates blood pressure through actions of the
brain and the kidneys.