Final answer:
In apoptosis, the extrinsic pathway is responsible for cell death initiated by external signals, playing a crucial role in both T-cell development and embryological morphogenesis such as the separation of fingers and toes. It maintains homeostasis by eliminating cells that are potentially dangerous.
Step-by-step explanation:
In apoptosis, the extrinsic pathway is triggered by outside instructions as part of a normal developmental program, or if the cell has been transformed (neighboring cells can detect this and send pro-apoptotic instructions).
External signaling can initiate apoptosis through various mechanisms. For instance, during T-cell development, external signals ensure that T-cells do not target the body's own proteins by initiating apoptosis of any T-cell that binds to self-proteins.
Similarly, in normal embryological development, such as the separation of fingers and toes, apoptosis plays a vital role in removing unneeded cells, allowing for proper morphogenesis.
Furthermore, cell death via apoptosis is essential for maintaining homeostasis within the body. It allows for the controlled removal of damaged, superfluous, or potentially dangerous cells without releasing harmful molecules. This is critical for preventing conditions such as cancer, where cells can proliferate out of control.