Human tooth of dentin. Other cells in the pulp include fibroblasts, preodontoblasts, macrophages and T lymphocytes. The pulp is commonly called "the nerve" of the tooth. Tooth development is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. Although many diverse species have teeth, their development is largely the same as in humans. For human teeth to have a healthy oral environment, enamel, dentin, cementum, and the periodontium must all develop during appropriate stages of fetal development. Primary teeth start to form in the development of the embryo between the sixth and eighth weeks, and
Eggshell the uterus. The egg can take up fluids and grow in size during this process, and the final, most rigid layer is not added until the egg is full-size. Hatching birds, amphibian and egg-laying reptiles have an egg-tooth used to start an exit hole in the hard eggshell. Eggshell waste is fundamentally composed of calcium carbonate, and has the potential to be used as raw material in the production of lime. Eggshell An eggshell is the outer covering of a hard-shelled egg and of some forms of eggs with soft outer coats. Insects and other arthropods lay a variety of