Human heart (mitral valve) tissue displaying calcification

Density-dependent colour scanning electron micrograph of the surface of human heart valve (mitral valve) tissue. The spherical particle in the centre of the image (yellow/green) is dense, calcified material composed of calcium phosphate. This build up of calcium salts (a process called calcification) will over time harden the tissue and can eventually stop the valve from working properly. The remaining material is less dense and corresponds to the organic component of the tissue. Micrographs were coloured in post-processing by combining images acquired by three modes of image acquisition that use different kinds of electron microscope detectors. Horizontal width of image is 11 microns.