Practice question

Stem cell hierarchy includes long-lived quiescent stem cells, short-lived rapidly cycling transit-amplifying cells, and terminally differentiated cells. Transit-amplifying cells are committed progenitors derived from stem cell division, undergoing limited rounds of symmetric divisions to expand progenitor pool before terminal differentiation. Found in intestinal crypts, epidermis, and testes, they increase proliferative output while protecting stem cells from replication stress and mutation accumulation. They express differentiation markers like EGF receptor and have reduced self-renewal. Understanding this intermediate amplification stage explains how small stem pools generate large numbers of differentiated tissue cells efficiently.