Previous Awards

View the images from our previous Award winners.

Hardening of heart tissue

Sergio Bertazzo

Download this image from Wellcome Collection.

Scanning electron micrograph of the surface of human heart valve (aortic valve) tissue. Clumps of calcium salts (the spherical structures coloured orange) are building up on the heart valve through a process called calcification. Over time this hardens the soft tissue and can eventually stop the valve from working properly, leading to heart disease. This image was produced using a technique called density-dependent colour scanning electron microscopy, which takes into account the physical surface features of the material as well as its density. In this image the orange colour identifies denser, calcified material, while structures that appear in green are less dense. The width of the image is 64 micrometres (0.064 mm).

How was this image made?

This image was produced using a type of scanning electron microscopy called density-dependent colour scanning electron microscopy. In this method, images are taken of a sample using two different detectors, one which records topographical information about the surface of the sample and one which records information about its density. A different colour is assigned to each and the images are then superimposed to produce a composite image like the one you see here. In this particular image, the orange colour identifies denser material (calcified material composed of calcium phosphate), while structures that appear in green are less dense (corresponding to the organic component of the tissue).

Why does calcification occur?

Calcification is the process by which calcium builds up in tissues in the body, causing them to harden. This can be either a beneficial or a detrimental process depending on where it is occurring. For example, depositing calcium in bones and teeth is desirable, whereas a build-up of calcium in soft tissues such as arteries, heart valves or the breast is less so. Unwanted calcium deposits harden soft tissues over time, which can stop them from working and functioning properly. These deposits can usually be seen in X-rays. Ageing, inflammation, tissue injury, parasitic infection, vitamin K deficiency and poor calcium absorption can all cause calcium deposits to form. For another example of calcification, see our award-winning image of a kidney stone.