Introduction

The human body consists of hundreds of cell types, all originating from the fertilized egg. During the embryonic
and foetal periods, cells increase dramatically in number, mature and become specialized to form tissues and
organs. Lots of cells are formed also in the adult body – more than a thousand billion cells each day. To counter
cell production and maintain an appropriate number of cells in the tissues, extensive cell death occurs both in the
foetus and in the adult. This delicate, controlled elimination of cells is called programmed cell death.

In the human foetus, the interdigital mesoderm, initially formed between fingers and toes, is removed by programmed cell death.	The intestinal lumen and other tissues are sculpted by programmed cell death.