Final answer:
The living tissue under the enamel of a tooth, which contains blood vessels and nerves, is known as dentin. It is a bone-like tissue that, along with the pulp cavity, provides the necessary vitality for a tooth's health and function.
Step-by-step explanation:
The living tissue of teeth underneath the enamel that contains blood vessels and nerves is called dentin. Dentin is a bone-like tissue that forms the bulk of the tooth underneath the crown and above the innermost part called the pulp cavity. The pulp cavity, inclusive of the pulp chamber at the top of the tooth and the pulp canal or root canal, contains the pulp which is rich in blood vessels, connective tissue, and nerves. Similarly to bone tissue, dentin is a living tissue that is sensitive and vital to the tooth's function and health.
The crown of the tooth is covered with enamel, which is the hardest substance in the body, designed to withstand the forces of biting and chewing. The root of the tooth and parts of the crown are also covered with cementum, which helps to anchor the tooth within the jaw bone via the periodontal ligament. The surrounding soft tissues, known as the gums or gingiva, support the maintenance of healthy teeth by securing them within the alveolar processes.