All except the filiform papillae are associated with taste buds. Examples are hairs, glandular hairs, scales, and papillae. In foliate papillitis the foliate papillae appear swollen. Neutrophils produce pus in the dermal papillae, generating characteristic blisters. The tongue's upper surface (dorsum) is covered by taste buds housed in numerous lingual papillae. Dietary isoflavones increase IGF production in scalp dermal papillae in transgenic mice. The exception to this are the filiform papillae that do not contain taste buds. The number and size of filiform papillae may be reduced. The exception to this is the filiform papillae that do not contain taste buds. The spiracular disc is usually surrounded by lobe-like projections and anal papillae or lobes. Other characteristics include a multicellular stigma, with shallow papillae or ridges. The dorsal surface of the mantle bears three pairs of large, flat, flap-like papillae. They are fine, small, cone-shaped papillae covering most of the dorsum of the tongue. This "papillary duct" exits the renal pyramid at the renal papillae. This refers to the circular mucosal elevation which surrounds the circumvallate papillae.