Hairy tongue is associated with hypertrophy of:
Hairy Tongue:

Characterized by hypertrophy of Filiform papillae with lack of normal desquamation
Dorsal surface of tongue gives thick matted appearance
Extrinsic stains may color the tongue from, white to brown to black.
Filiform papillae.
Fungiform papillae.
Circumvallate papillae.
Foliate papillae.