Tooth anatomy. Animation showing the internal anatomy of a human tooth. In the centre of the tooth is the pulp (red), which contains the blood and nerve supply. This is surrounded by dentin (yellow), a mineralised connective tissue. The crown of the tooth, the part above the gum line, has an outer layer of enamel. It is the hardest substance in the human body, composed of rows of calcium and phosphorus salts embedded in a protein matrix. HD supplied with alpha, or for a flat version on a black background, see clip K003 3666.