Nephrotome
Encyclopedia
The nephrotome is a section of the mesoderm
. It gives rise to the pronephros
and eventually to the rest of the kidney
.
A nephrotome is an obsolete term used to describe rounded mesodermal portions of the forming pronephros. In old texts the pronephros is described as forming through the fusion of multiple nephrotomes. Modern visualization methods such as scanning electron microscopy, in situ hybridization
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 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 become the dorsal branches of the pronephros that link to nephrostomes (distinct from nephrotomes). These rounded bumps are probably the structures observed in histological sections that are referred to as nephrotomes. Nephrostomes are thin ciliated funnels that link pronephric nephrons to the ceolom, and are not related to nephrotomes.
Mesoderm
In all bilaterian animals, the mesoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm and endoderm , with the mesoderm as the middle layer between them.The mesoderm forms mesenchyme , mesothelium, non-epithelial blood corpuscles and...
. It gives rise to the pronephros
Pronephros
Pronephros 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 amniotes the mesonephros is the embryonic kidney and a more...
and eventually to the rest of the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
.
A nephrotome is an obsolete term used to describe rounded mesodermal portions of the forming pronephros. In old texts the pronephros is described as forming through the fusion of multiple nephrotomes. Modern visualization methods such as scanning electron microscopy, in situ hybridization
In situ hybridization
In situ hybridization is a type of hybridization that uses a labeled complementary DNA or RNA strand to localize a specific DNA or RNA sequence in a portion or section of tissue , or, if the tissue is small enough , in the entire tissue...
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 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 become the dorsal branches of the pronephros that link to nephrostomes (distinct from nephrotomes). These rounded bumps are probably the structures observed in histological sections that are referred to as nephrotomes. Nephrostomes are thin ciliated funnels that link pronephric nephrons to the ceolom, and are not related to nephrotomes.