Embryonic stem cells (ESCs) are stem cells derived from the undifferentiated inner mass cells of a human embryo.

Embryonic stem cells are pluripotent, meaning they are able to grow (i.e. differentiate) into all derivatives of the three primary germ layers: ectoderm, endoderm and mesoderm.

In other words, they can develop into each of the more than 200 cell types of the adult body as long as they are specified to do so.

Embryonic stem cells are distinguished by two distinctive properties: their pluripotency, and their ability to replicate indefinitely.

ES cells are pluripotent, that is, they are able to differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm, and mesoderm.

These include each of the more than 220 cell types in the adult body.

Pluripotency distinguishes embryonic stem cells from adult stem cells found in adults; while embryonic stem cells can generate all cell types in the body, adult stem cells are multipotent and can produce only a limited number of cell types.

Additionally, under defined conditions, embryonic stem cells are capable of propagating themselves indefinitely.

This allows embryonic stem cells to be employed as useful tools for both research and regenerative medicine, because they can produce limitless numbers of themselves for continued research or clinical use.

Because of their plasticity and potentially unlimited capacity for self-renewal, ES cell therapies have been proposed for regenerative medicine and tissue replacement after injury or disease.

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Embryonic stem cell - Science Daily