What are the biological mechanisms underlying physiological and reparative regeneration.

Physiological regeneration – the restoration of parts of the body that have worn out during the life process It acts throughout the ontogenesis, maintains the constancy of structures, despite cell death. Intensive processes of physiological regeneration during the restoration of blood cells, epidermis, mucous membranes. Examples are molting of birds, tooth growth in rodents. Physiological regeneration occurs not only in tissues with intensely dividing cells, but also where cells divide slightly. 25 out of 1000 hepatocytes die and the same amount is restored. Physiological regeneration is a dynamic process that includes cell division and other processes. The provision of functions underlies the normal functioning of the body.
Reparative regeneration – restoration of damaged tissues and organs after emergency impacts. With complete regeneration, the complete original structure of the tissue is restored after its damage, its architecture remains unchanged. Distributed in organisms capable of asexual reproduction. For example, white planaria, hydra, mollusks (if you remove the head, but leave the nerve-node structure). Typical reparative regeneration is possible in higher organisms, including and man. For example, in the elimination of necrotic organ cells. In the acute stage of pneumonia, destruction of the alveoli and bronchi occurs, then recovery occurs. Under the influence of hepatotropic poisons, diffuse necrotic changes in the liver occur. After the cessation of the action of poisons, architectonics is restored due to the division of hepatocytes – cells of the hepatic parenchyma. The original structure is restored. Homomorphosis – restoration of the structure in the form in which it existed before destruction. Incomplete reparative regeneration – the regenerated organ differs from the removed one – heteromorphosis. The original structure is not restored, and sometimes, instead of one organ, another organ develops. For example, the eye has cancer. When removed, in some cases, an antenna develops. In humans, the liver regenerates similarly when a portion of the hepatic lobe is removed. There is a scar and 2 to 3 months after the operation, the mass of the liver is restored, and the restoration of the shape of the organ does not occur. This is due to removal and damage to the connective tissue during surgery.

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