primary urine

The fluid that is filtered from the capillary blood into Bowman's space is called filtrate or primary urine.

The action of the branchial hearts is necessary for the production of primary urine in these appendages via pressure filtration.

Although freely filtered not all PAH crosses into the primary urine within Bowman's capsule.

The primary urine produced by filtration of blood (or a similar functioning fluid) is modified into secondary urine through selective reabsorption by the cells lining the metanephridium.

Malpighian tubules secrete primary urine, most of which is passed into the hindgut where water, ions and essential metabolites are reabsorbed before the fluid is excreted.