Types of regeneration process

Regeneration is one of the processes in which if an organism is cut into several pieces, each of its parts regrows to the original state. This process is carried out by specialized cells called stem cells. It takes place in organisms that have a very simple structure with very few specialized cells.
There are two types of regeneration:
Morphallaxis: This type of regeneration has little growth and depends upon tissues repatterning. For eg., Hydra grows by loss of cells from its end and by budding. When cut into two, the upper part develops into foot while the lower part develops into the head. The formation of nearby heads is inhibited by the head region.
Epimorphosis: This type of regeneration depends upon the growth of new and properly patterned structures. For eg., regeneration of a vertebrate limb. It involves cell dedifferentiation and growth. The epidermal cells form a blastema. The blastema gives rise to structures with positional distal values. Retinoic acid changes proximal-distal values in limb regeneration.