Blood vessels are the hollow tubular structures through which blood circulates throughout the body. There are three main types: arteries (which carry oxygenated blood away from the heart under high pressure), veins (which return deoxygenated blood to the heart under lower pressure), and capillaries (the smallest vessels, forming a network in the tissues where oxygen, nutrients, and waste products are exchanged between the blood and cells).
Arterial walls are thick and muscular, allowing them to withstand the high pressure generated by the heart’s pumping action and to regulate blood flow through vasoconstriction (narrowing) and vasodilation (widening). Venous walls are thinner; many veins contain one-way valves that prevent backflow of blood, particularly in the legs. Capillary walls are extremely thin (just one cell thick) to facilitate the diffusion of gases and nutrients.
Disease of the blood vessels (vascular disease) is a major cause of morbidity and mortality. Atherosclerosis (fatty plaque build-up in arterial walls) affects the coronary arteries (causing coronary artery disease), the cerebral arteries (causing stroke), and the peripheral arteries (causing peripheral vascular disease). Vasculitis (inflammation of blood vessel walls) and aneurysms (abnormal dilation of vessel walls) are other important conditions.
For cardiac arrest survivors, the health of the coronary blood vessels (the arteries supplying the heart muscle itself) is often the central focus of investigation and treatment. Coronary angiography directly visualises the coronary blood vessels and guides decisions about revascularisation.
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