Images Dated 10th March 2003

Black hole

Black hole, conceptual computer artwork. Matter is spiralling into the black hole, dragged by immense gravitational forces. This will cause the material to give off high-energy X-rays. A black hole is formed when the core of a star collapses under its own weight, increasing its gravitational field to the point where, beyond a boundary known as the event horizon, nothing, not even light, can escape. This leads to its black appearance. Only sufficiently massive stars form black holes, doing so when they have used up the fuel that sustained their nuclear fires. This results in a loss of outwards heat pressure, allowing the total collapse that forms the black hole

© MEHAU KULYK/SCIENCE PHOTO LIBRARY

Artwork showing structure of human skeletal muscle

Skeletal muscle. Illustration of the structure of human skeletal muscle. Skeletal muscle (top right) consists of bundles of long, thin cells called muscle fibres. A group of five muscle fibres with surrounding blood vessels is shown at centre. Each muscle fibre contains numerous "myofibrils", one of which is shown at lower centre. The myofibril is a bundle of two types of protein "myofilament": myosin (green) and actin (red). When the muscle is stimulated, tiny cross-bridges (lower left) in the myosin filaments hook onto actin filaments and pull them along. As a result, myosin and actin filaments slide over each other, shortening the muscle and making it contract

© JOHN BAVOSI/SCIENCE PHOTO LIBRARY

Bronchitis

Bronchitis. Cutaway artwork of a lung showing the effects of bronchial inflammation (bronchitis). The airways of the lungs (bronchi), respond to an infection by becoming inflamed and producing mucus that is coughed up as sputum (phlegm, yellow). The mucus is seen inside the bronchi of the left lung (at right). Bronchitis also causes shortness of breath because the airways become narrowed. It is associated with both smoking and air pollution. With chronic bronchitis there is no cure and the functioning of the lungs steadily becomes reduced. The heart (lower left), pulmonary arteries (blue, centre left), vena cava veins (blue, far left) and the aorta (main body artery, red) are also seen

© John Bavosi/Science Photo Library