Here's a picture of an extracted tooth with its nerve root still attached. The tooth has two anatomical parts: the crown and the root. Crown can be seen above the gum line and its shape determines its function. Root is deeply embedded below the gum line. Tooth pulp is soft consisting of living blood vessels, connestive tissue and large vessels. There are plenty of reasons which causes a sharp, growing, throbbing or shooting pain. Some of them include pulpitis, abscess formation, dental caries and many more.