Papula

For the skin condition, see papule.

Papulae (sing. papula; also occasionally papulla, papullae), also known as dermal branchiae or skin gills, are projections of the coelom of Asteroidea that serve in respiration and waste removal^[1]. Papulae are soft, covered externally with the epidermis, and lined internally with peritoneum. They extend through the mesodermal ossicles and are protected from microscopic larvae by pedicellariae. In a living specimen, the dermal gills can be extended or withdrawn.