Light micrograph of normal human sinew (tendon). Tendon is an example of regular connective tissue, and is inelastic. It consists of parallel arrays of collagenous fibres produced by cells known as fibroblasts. The fibres are arranged in bundles; the primary bundles are surrounded by fibroblasts; groups of primary bundles, called secondary bundles are separated by areolar tissue. This longitudinal section of a tendon shows fibre bundles running horizontally, in shades of red. The dark spots are cell nuclei and the white spaces represent the areolar tissue between the bundles. Magnification: x100 at 35mm size.