The tooth is broken into 3 sections. The crown, the neck, and the root. The crown of the tooth is the structure of the tooth that we see and that is used for the function of chewing and breaking down food. The neck is the portion of the tooth at the gumline that we partially see. The root is the section of the tooth that is below the gumline and the part of the tooth that connects to the bone and feeds the tooth with blood supply to keep the tooth alive.
The main components of teeth are enamel, dentin, and the pulp.
Enamal is a hard tissue that is the outermost part of the tooth. Enamel is calcified tissue that is hard, but can be chipped, broken, or worn out from decay.
Dentin is the portion of tooth that is directly beneath the enamel. The dentin is a structure of the tooth that contains microscopic tubules that come in contact with the pulp of the tooth. With these tubules, it is a passageway that allows cold and heat to reach the nerves of the tooth. When people have tooth sensitivity, it is usually because the enamel has been worn down and sensations are reaching the nerve more easily.
The pulp consists of blood supply and nerves inside of the tooth. Yes, each tooth is alive with nerves and blood in a healthy tooth. This is why we can feel pain in our teeth from sensations or damage.