Epimorphosis: In this type of regeneration, the lost or damaged body part is replaced by the proliferation and differentiation of cells at the site of the injury.
Morphallaxis: Here, the existing cellschange their structure and function to compensate for the lost or damaged body part, without significant cell proliferation. This type of regeneration is observed in hydra and some other simple organisms.
Blastema Formation: This type involves the formation of a mass of undifferentiated cells, known as a blastema, at the site of the injury. The blastema then differentiates into the specific tissues and structures needed for regeneration. This type is commonly observed in amphibians and certain fish.
Regeneration in Planaria
The flatworm Planaria is often studied in the context of regeneration due to its remarkable regenerative abilities. When a planarian is cut into pieces, each piece has the potential to regenerate into a complete organism. This is due to the presence of pluripotent stemcells in planaria, which can give rise to any type of cell needed for regeneration.
While humans do not possess the remarkable regenerative abilities of certain animals, there are some instances of regeneration in humans. For example, the liver has the ability to regenerate to its original size after partial removal. Additionally, the skin is capable of regeneration to heal wounds, albeit with the formation of scar tissue.
Regeneration in Salamanders
Salamanders are known for their exceptional regenerative abilities. If a salamander loses a limb, it can regrow a fully functional limb, complete with bones, muscles, nerves, and blood vessels. This process involves the formation of a blastema at the site of the injury, which then differentiates into the various tissues needed for the new limb.
Study Guide for Regeneration
To understand regeneration, it is important to grasp the concepts of cell proliferation, differentiation, and the role of stemcells. Here are some key topics to focus on when studying regeneration: