1.1 The circulation
The circulatory system is required to perfuse the tissues of the body with a medium suitable to maintain cell life. It delivers oxygen and nutrients and removes waste products for elimination by the kidneys, liver and lungs. Effective circulation depends on normal electrical activation and mechanical function of the heart, normal cardiac structure and appropriate regulation. The important components of the circulatory system are the heart, great arteries (aorta and pulmonary artery), arterioles, capillaries, venules, great veins and lymphatics. The system is divided into two circuits in series, one supplying systemic requirements and the other serving the pulmonary tissues.
Control of the cardiovascular system is mediated by regulatory centres in the brain via the autonomic nervous system (ANS). The ANS has a neural and a humoral component. Regulation takes place at the level of the heart, vessels and local tissues. In addition, mechanisms regulating renal function and respiration have a profound effect on the cardiovascular system.