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.
Drug-Induced Black Hairy Tongue: Diagnosis and Management Challenges. âBlack hairy tongueâ (BHT), also known as lingua villosa nigra, hyperkeratosis of the tongue, nigrities linguae, keratomycosis linguae, and melanotrichia linguae, is a benign disorder characterized by hypertrophy of the filiform papillae. Lusitanus, who is credited with the original description of black hairy tongue, reported this condition in 1557.