Induction, Development, and Physiology of the Pronephric Tubules

This chapter explores the biology of the vertebrate pronephros in greater depth. The chapter covers each of the functional components: (1) the tubules, which perform the resorptive and excretory functions of the pronephros, (2) the glomus, its filtration unit, and (3) the duct, which disposes of the urine and may participate in the regulation of acid-base balance and plays a key role in the induction of the adult kidneys. Pronephric cells are specified during gastrulation in amphibians. However, the first visible sign of pronephric morphogenesis occurs some 10 to 12 hours later when patterning of the pronephros subdivides the pronephric region into the precursors of the pronephric tubules, duct, and glomus. In amphibian early neurulae, the somites lie below the neural plate and by this stage the pronephric anlage lies lateral to the neural plate and posterior to the restriction that marks the border between the presumptive hindbrain and spinal chord in both urodeles and anurans. The pronephros forms between the paraxial mesoderm and the lateral plate, just behind the head.