Unlike the equator and the Tropic of Cancer and the Tropic of Capricorn, the Prime Meridian and all lines of longitude are completely imaginary lines and have no significance with regard to the Earth or to its relationship with the sun.
Black hairy tongue typically results when projections on the tongue called papillae grow longer and don't shed like normal. This makes the tongue look hairy. Debris, bacteria or other organisms can collect on the papillae and result in discoloration. The cause of black hairy tongue can't always be determined.
Blister on tip of the tongue. What causes blisters on the tip of your tongue? This condition is commonly caused by injuries. There are also some other conditions like infections that can cause this condition. The blisters can be small, big, multiple or clustered. White bumps and spots begin to show when the condition begins to heal.