Annelid anatomy

thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion

The nephridium (: nephridia) is an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys (which originated from the chordate nephridia). Nephridia remove metabolic wastes from an animal's body and come in two basic categories: metanephridia and protonephridia. In some cases, nephridia may fuse or become functionally integrated with coelomoducts—mesodermal structures that open from the coelom to the exterior—to form a more complex structure known as a nephromixium. All animals possessing nephridia or kidneys belong to the clade Nephrozoa.

skeleton supported by fluid pressure

thumb|Specimen of the annelid, Lepidonotus|Lepidonotus oculatus, with a microscope image of one of its parapodia (inset). [[Museums Victoria specimen.]] In invertebrates, the term parapodium (Gr. para, beyond or beside + podia, feet; : parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed lateral outgrowths that bear the chaetae. In several groups of sea snails and sea slugs, 'parapodium' refers to lateral fleshy protrusions. __TOC__

thumb|Earthworm with clitellum lablelled. thumb|Close-up of the clitellum of a Lumbricus rubellus The clitellum is a thickened glandular and non-segmented section of the body wall near the head in earthworms and leeches that secretes a viscid sac in which eggs are stored. It is located near the anterior end of the body, between the fourteenth and seventeenth segments. The number of the segments to where the clitellum begins and the number of segments that make up the clitellum are important for identifying earthworms. In microdrile earthworms, the clitellum has only one layer, resulting in a s

specialised attachment organ of an animal

thumb|upright=1.5|Augenerilepidonotus|Augenerilepidonotus dictyolepis specimen from Museums Victoria showing the prostomium with notable structures labelled

long, thin structures in both vertebrate and invertebrate animals

major structure of the invertebrate central nervous system

thumb|Specimen of the annelid, Lepidonotus|Lepidonotus oculatus showing its chaetae projecting laterally, with a microscope image of one of its parapodia and chaetae (inset). [[Museums Victoria specimen.]]

chloragogen cell are star shaped cells

The periproct is the final body segment in annelid worms. The anus is located on this segment. The term also refers to the small region surrounding the anus of the sea urchin.