As you read this, your blood is streaming inwards and outwards - converging in veins from all parts of your body, turning through the entwined but separate streams through the right and left sides of the heart, moved forwards by the rhythmic contraction of heart muscle and the closing and opening of valves.

Blood is propelled from the heart through arterial branches to the microscopically fine capillary webs of organs throughout the body. Such a richly varied fluid system cannot be captured in words or pictures alone.

Medical imaging gives only glimpses of parts of the system and it is a challenge to even begin to appreciate the complexity and dynamic beauty of the circulatory system as a whole.

Blood circulation and heart maintain unity in diversity, and continuity through continual change. The heart is responsive and active, responding to and serving the changing needs of the body.

The seeping of blood through billions of varied and microscopically fine capillary branches and, at the same time, the flows and counter-flows in branches of veins and arteries, and the sinuous streams swirling through the curvatures of the heart - these are awesome in their complexity, unity and beauty of form.

They continue reliably, day and night, life-long.