Metanephros

Metanephros is the third and final excretory organ that develops in a vertebrate, typically a mammal, during its embryonic development stage. It is the permanent and definitive kidney, which continues to function into adulthood. The metanephros is preceded by the pronephros and the mesonephros, which serve as temporary kidneys during the early stages of embryonic development.

Development

The metanephros begins to develop in the fifth week of embryonic life. It originates from two sources: the ureteric bud and the metanephric mesenchyme. The ureteric bud is an outgrowth of the mesonephric duct, while the metanephric mesenchyme is a group of tissue that migrates from the intermediate mesoderm.

The interaction between the ureteric bud and the metanephric mesenchyme is crucial for the development of the metanephros. The ureteric bud invades the metanephric mesenchyme, inducing it to differentiate and form the nephrons, the functional units of the kidney. The ureteric bud itself gives rise to the collecting system of the kidney, including the ureters, renal pelvis, calyces, and collecting tubules.

Structure

The metanephros is composed of millions of nephrons, each of which is a functional unit of the kidney. Each nephron consists of a renal corpuscle (comprising a glomerulus and Bowman's capsule) and a renal tubule. The renal corpuscle filters the blood to form a filtrate, which then passes through the renal tubule where it is modified to form urine.

Function

The primary function of the metanephros is to filter waste products from the blood and excrete them in the form of urine. It also plays a crucial role in maintaining the body's electrolyte balance and blood pressure, and in the regulation of red blood cell production through the secretion of the hormone erythropoietin.

Clinical significance

Abnormalities in the development of the metanephros can lead to various congenital kidney diseases, such as renal agenesis (absence of one or both kidneys), renal dysplasia (malformation of the kidneys), and polycystic kidney disease (formation of multiple cysts in the kidneys).

File:Metanephros.jpg

Development of the metanephros

See also

• Nephron
• Kidney development
• Renal physiology