Metanephros kidney formed from the :

Question

Accepted Answer

The correct option is 3: Posterior end of the nephrogenic mesoderm.

The development of the vertebrate kidney is a classic study in embryology, progressing through a phylogenetic sequence of three successive, transitory forms: the pronephros, the mesonephros, and the metanephros. All three kidney types arise from a longitudinal mass of tissue called the nephrogenic cord, which is derived from the intermediate mesoderm. The metanephros, which serves as the permanent, functional kidney in higher vertebrates such as reptiles, birds, and mammals (including humans), is specifically formed from the caudalmost, or posterior, portion of this nephrogenic mesoderm. This region condenses into a tissue mass known as the metanephric blastema. The formation of the metanephros is crucially dependent on a reciprocal inductive interaction between this metanephric mesoderm and the ureteric bud, an outgrowth of the mesonephric (Wolffian) duct. While the ureteric bud develops into the collecting system (ureter, renal pelvis, calyces, and collecting ducts), the posterior nephrogenic mesoderm is entirely responsible for forming the functional components of the kidney—namely, the filtration units or nephrons.

The incorrect option is 1: Anterior end of pleuroperitoneal cavity.

The pleuroperitoneal cavity refers to the embryonic body cavity that will later be partitioned to form the pleural cavity (housing the lungs) and the peritoneal cavity (housing abdominal organs). This cavity is formed by the folding of the lateral plate mesoderm. The kidney, however, is derived from the intermediate mesoderm. These two mesodermal lineages are distinct, and the lateral plate mesoderm is not involved in the formation of the excretory organs. Therefore, the anterior end of the pleuroperitoneal cavity has no direct role in the development of the metanephros kidney.

The incorrect option is 2: Middle part of intermediate coelom.

This terminology is imprecise, as the kidney originates from the *intermediate mesoderm*, not an "intermediate coelom." More critically, the **middle** portion of the nephrogenic cord gives rise to the **mesonephros**. The mesonephros is a transient, functional kidney in fish and amphibians, but in mammals, it only functions briefly during early embryonic life before most of its tubules degenerate. The derivatives of the mesonephros are associated with the male reproductive tract, such as the epididymis and ductus deferens, rather than the definitive metanephros kidney.

The incorrect option is 4: Anterior part of intermediate coelom.

As with Option 2, the use of "intermediate coelom" is not the correct anatomical term for the embryonic kidney tissue, which is the intermediate mesoderm or nephrogenic cord. The **anterior** portion of the nephrogenic cord is responsible for forming the **pronephros**. The pronephros is the most rudimentary and earliest kidney structure to appear in vertebrate development, typically forming vestigial tubules that rapidly regress and are non-functional in amniotes (reptiles, birds, mammals). Thus, the anterior part is associated with a temporary, non-permanent kidney, not the adult metanephros.