tissue homeostasis

Tissue homeostasis is the steady balance a tissue keeps between cells being born and cells dying, so that its size and function stay roughly constant over time. It is the body's version of a well-run bathtub: the tap of new cells and the drain of old ones are tuned to each other, so the water level — the amount of working tissue — holds steady even though the water is always flowing.

Most tissues are quietly replacing themselves all the time. Your skin sheds and rebuilds over weeks, the gut lining turns over in days, and blood is constantly remade, all without you noticing, because new cells are produced at almost exactly the rate old ones are lost. Stem and progenitor cells supply the fresh cells; controlled cell death removes the worn-out ones.

When this balance tips, trouble follows: too much cell death (or too little replacement) wastes a tissue away, while too much division with too little death is one of the roads toward cancer. Regeneration is essentially homeostasis pushed into high gear after damage — so understanding the everyday balance is the foundation for understanding repair.