Dentin tubules are small, hollow microscopic channels that travel from the inside of the tooth (where the pulp is) out through the dentin, ending right beneath the enamel. Dentin is the middle layer of the tooth, forming the bulk of the tooth. The inside of your tooth is fed by blood vessels, but the outer layers of your teeth don't contain blood vessels or nerves. Dentinal tubules do the blood vessels' work in the harder layers of your teeth, carrying the pulp chamber's nutrients and fluids to your dentin layer.