Regeneracja całego ciała

Animals across diverse phyla exhibit varying regeneration capacity, including regenerating tissues, organs, or even the entire body from small injury remnants. 

Planaria are flatworms extensively used as model organisms to study regeneration.

They demonstrate extraordinary regenerative abilities owing to a population of adult somatic stem cells, called neoblasts, present throughout their bodies. These cells can divide to produce all types of planarian cells.

After an injury, the wound site first contracts to minimize the surface area, followed by the production of a protective mucosal covering.

The neoblasts then divide throughout the planarian body. This global increase in the neoblast population is followed by a more localized division at the wound site, generating an undifferentiated mass of cells called a blastema.

The blastema then differentiates to form lost tissues and organs. But how do the neoblasts determine which structures need regeneration?

For instance, when a planarian is cut in half transversely, the head needs to regenerate the tail, and the tail needs to regenerate the head. This is regulated by signaling pathways, such as Wnt, that control regeneration polarity.