Papula
Encyclopedia
Papulae also known as dermal branchiae or skin gills, are projections of the coelom
of Asteroidea that serve in respiration
and waste removal
. Papulae are soft, covered externally with the epidermis, and lined internally with peritoneum
. They extend through the mesoderm
al ossicles and are protected from microscopic larvae by pedicellariae
.
Coelom
The coelom is a fluid-filled cavity formed within the mesoderm. Coeloms developed in triploblasts but were subsequently lost in several lineages. Loss of coelom is correlated with reduction in body size...
of Asteroidea that serve in respiration
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
and waste removal
Excretion
Excretion is the process by which waste products of metabolism and other non-useful materials are eliminated from an organism. This is primarily carried out by the lungs, kidneys and skin. This is in contrast with secretion, where the substance may have specific tasks after leaving the cell...
. Papulae are soft, covered externally with the epidermis, and lined internally with peritoneum
Peritoneum
The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in amniotes and some invertebrates...
. They extend through the mesoderm
Mesoderm
In all bilaterian animals, the mesoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm and endoderm , with the mesoderm as the middle layer between them.The mesoderm forms mesenchyme , mesothelium, non-epithelial blood corpuscles and...
al ossicles and are protected from microscopic larvae by pedicellariae
Pedicellariae
A pedicellaria is a small wrench or claw-shaped structure commonly found on Echinoderms, particularly in sea stars and sea urchins...
.