The cardiovascular system is composed of the heart, blood vessels, or vasculature, and the cells and plasma that make up the blood. The blood vessels of the body represent a closed delivery system, which functions to transport blood around the body, circulating substances such as oxygen, carbon dioxide, nutrients, hormones and waste products. There are three main types of blood vessel:

• Veins - the efferent blood vessels that return blood to the heart;
• Arteries - the afferent blood vessels that carry blood away from the heart;
• Capillaries - narrow, thin-walled blood vessels that form networks within the tissues

Arteries branch and diverge as they move away from the heart. As they form smaller and smaller divisions, they eventually terminate in capillaries. By contrast, veins merge and converge into successively larger blood vessels as they move towards the heart. Capillaries networks are the site of gas, nutrient and waste exchange between the blood and the respiring tissues.

The principal function of the heart is to continuously pump blood around the cardiovascular system. It receives both sympathetic and parasympathetic nerve fibres which alter the rate of the beat, but they do not initiate the contraction. Instead, this is controlled by autorhythmic cells. Surrounding the heart is the coronary circulation. These blood vessels supply the respiring cardiac tissues with essential oxygen and nutrients and also remove metabolic waste products.

As part of the Physiome Project, the Heart Research Group at the Bioengineering Institute is developing an integrated model of the heart, incorporating electrical activation, mechanical contraction, energy supply and utilisation, cell signalling and many other biochemical processes. The aim of the project is to develop an anatomically based and biophysically detailed mathematical model of the heart for use by medical scientists and clinicians in research, teaching and clinical practice. The model includes a range of spatial and temporal scales, from the level of the protein and cell, to the whole organ, and ultimately to integration with other organ systems in the Auckland Bioengineering Institute's virtual human.