nephrostome

A nephrostome is the ciliated, funnel-shaped opening of a nephridium into the body cavity. In some primitive vertebrates, like the pronephros, nephrostomes filter fluids from the body cavity and bloodstream to produce urine. The archinephros, an ancestral vertebrate kidney, also features nephrostomes where tubules connect to the body cavity. While the term "nephrostome" is specific to this opening, the broader concept of nephrons as the functional units of kidneys, producing urine through filtration and secretion, is found in more advanced systems. The term nephridiostome is synonymous with nephrostome.12345