Which Organ Regenerates Itself?

The liver extraordinary regenerative capacity has been known since antiquity — the Greek myth of Prometheus, whose liver was eaten by an eagle each day only to regrow overnight, may reflect ancient awareness of this phenomenon. In reality, liver regeneration takes weeks to months, not hours. If up to 75% of the liver is removed (partial hepatectomy), the remaining portion can regrow to its original functional mass within 8-15 days in mice, or several weeks in humans. This is technically compensatory hyperplasia (existing cells enlarging and dividing to restore mass) rather than true regeneration of the original structure. The process is orchestrated by a complex cascade of growth factors (HGF, EGF, TNF-alpha, IL-6) and is so reliable that living-donor liver transplantation is possible — both the donated lobe and the donor remaining liver regrow to near-normal size. No other human internal organ comes close to this capacity, though skin, blood, and gut lining constantly self-renew.