A tooth is made of up of a number of highly specialised tissues. The enamel is the hard outer covering visible in the mouth. Below this is dentine, a less hard and porous material that makes up the majority of the tooth. The root of the tooth is often twice the length of the crown and is supported inside the jaw bone by a supporting ligament. Inside the body of the tooth is the pulp space, which contains blood vessels, nerves and connective tissue, called the pulp. This has a number of functions including tooth development and sensory and protective functions for the tooth during its life. The nerves and blood supply enter the tooth at the bottom of the root and reside in the root canals and in the main body of the tooth called the pulp chamber.