Pronephros

Pronephros is the primary kidney that develops in the embryo. It appears at an early stage of embryonic development and plays an important role in the formation of the renal system of the future organism.

However, despite its importance, the pronephros practically does not perform any functions in the embryo’s body and disappears relatively quickly. Typically the pronephros functions within 40-50 hours.

It is important to note that the pronephros may have different structure and function in different animal species. For example, in some species of fish the pronephros remains the main kidney throughout life, while in other species it is replaced by more complex kidney structures such as the mesonephros and metanephros.

Mesonephros and metanephros are more complex forms of kidneys that develop later in the embryo and perform more specialized functions such as filtering the blood and removing waste from the body.

In conclusion, pronephros is an important stage in the development of the body's renal system, which is the first step towards the formation of more complex and specialized renal structures.

The pronephros is a pronephros that develops in the embryo and functions for a short time, about 40-50 hours, after which it disappears. The pronephros does not perform any functions in the embryo, unlike the mesonephros and metanephros.

The mesonephros is the first kidney that begins to develop in the embryo at 3-4 weeks of pregnancy. It is responsible for the production of urine and the formation of the primary kidney. The mesonephros functions until the end of pregnancy and continues to work in the body after birth.

Metanephros is also a preference, but it begins to develop later, at 6-7 weeks of pregnancy. It also does not perform any important functions in the body and disappears after a few weeks of development.

Thus, the pronephros is a unique preference in that it develops in the embryo for a short period of time and then disappears without performing any functions. This may be due to the fact that the embryo is not yet ready to develop a full kidney, and the pronephros can be considered as a “spare” kidney in case the main kidneys fail to develop.

Pronephros have a long history of study in humans, starting in 1953 in connection with the advent of electron microscopic research methods in science. At that time, several groups of scientists managed to obtain microscopic images of the newly discovered formation, which some scientists described as a mesonephr, others - as a metanephros or even a preendocrine gland of endocrine origin. Research errors were associated with poor terminological accuracy and discrepancies in international and domestic literature, which was the reason for writing a separate article.

Later, many leading scientists such as O.K. Khmelnitsky, A.P. Fillipov and others participated in the discussion on this issue. The discussion continued for decades and ended with the official recognition of it as an independent rudiment of kidney development, or, as it is often called, the prebud, since it precedes the appearance of the mesonephros as an organ. The term “pronephron” was introduced in 1886 by A. Virchow based on the recognition of this structure as an anatomical unit of the organ, thus separating it from the term metanephron, used earlier (from σύν; σίωμμα - “budding”, “separation”). When dividing the term “metanephron,” a discrepancy arose with the translation of the name, which they tried to correct by calling it using the German term “mesonephron” and denying the earlier name.

After becoming familiar with the published works of several groups of scientists of the 20th century, already from the late 90s of the 20th century this structure began to be called pronephros, i.e. predecessor. The exceptionally rapid rate of growth of the pronephron is fairly consistent with the fact that it is a structure of endodermal origin, but some intrabud phase degeneration of epithelial cells also rules out an ectodermal origin for the structure. Moreover, according to G.M. Solovyov and A.Yu. Doroshenko (2004), it was for this reason that this structure disappeared after birth. Differences of opinion still exist regarding the acceptance of the term pronephron.