In earlier conceptions of

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

biology, the nephrotome was a section of the

mesoderm The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical ...

that gives rise to the

pronephros Pronephros is the most basic of the three excretory organs that develop in vertebrates, corresponding to the first stage of kidney development. It is succeeded by the mesonephros, which in fish and amphibians remains as the adult kidney. In am ...

and eventually to the rest of the

. Older texts describe the pronephros as forming through the fusion of multiple nephrotomes. Modern visualization methods, such as

scanning electron microscopy A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that ...

in situ hybridization ''In situ'' hybridization (ISH) is a type of Hybridisation (molecular biology), hybridization that uses a labeled complementary DNA, RNA or modified nucleic acid strand (i.e., a Hybridization probe, probe) to localize a specific DNA or RNA seq ...

, and confocal microscopy, combined with the simple approach of peeling off the epidermis to see the forming kidney, have shown that this is not the case. Nephric

mesenchyme Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood, or bone. The interactions between mesenchyme and epithelium help to form nearly ever ...

separates from the intermediate mesoderm as a single elongated primordia. As this primordia begins to undergo epithelialization the anterior portions of the pronephros form rounded protrusions, which then later became the dorsal branches of the pronephros that link to nephrostomes (distinct from nephrotomes). These rounded bumps are the structures observed in histological sections that are referred to as nephrotomes. Nephrotomes are not related to nephrostomes, which are thin ciliated funnels that link pronephric nephrons to the coelom.

External links

* {{Authority control Embryology of urogenital system Kidney