What is a stem cell?

A stem cell is defined as an undifferentiated cell capable of developing into various cell types. This unique characteristic allows stem cells to play a crucial role in growth, development, and tissue repair. Stem cells have the ability to divide and replicate indefinitely, which distinguishes them from fully differentiated cells that serve specific functions and cannot revert to a stem cell state.

This capacity for differentiation means that stem cells can give rise to multiple cell types, including those of the brain, heart, and skin, depending on the signals and conditions they are exposed to. This makes them essential for both embryonic development and cellular regeneration in adults.

In contrast, differentiated cells, which perform specialized functions, are already committed to a specific lineage and cannot transform into other cell types. Cells that have lost regenerative abilities are also not considered stem cells, as their capacity to contribute to healing and cellular turnover is impaired. Finally, the option related to hair follicles describes a limited function of a specific cell type rather than capturing the broader definition of stem cells, which encompasses their versatility and regenerative potential across diverse tissues.