2. What happens to the rapidly dividing cells when the healing process nears completion? Controls on Cell Division (pg. 250)

As the healing process approaches completion, the rapidly dividing cells undergo several regulatory changes to ensure that tissue restoration is properly finalized and excess cells are eliminated. Specifically: 1. **Cessation of Cell Division:** Growth factors and cellular signals that initially stimulated cell proliferation diminish, signaling the cells to stop dividing. This reduction in proliferative signals ensures that cell numbers return to normal levels. 2. **Differentiation:** Many of the proliferating cells begin to differentiate into their specialized cell types, taking on specific functions required for the fully healed tissue. This transition from a proliferative state to a differentiated state helps restore the tissue's normal structure and function. 3. **Apoptosis (Programmed Cell Death):** Excess cells that are no longer needed after healing may undergo apoptosis. This controlled cell death removes surplus cells without causing inflammation or damage to surrounding tissues. 4. **Regulatory Mechanisms:** Processes such as contact inhibition, where cells stop dividing once they occupy all available space, and checkpoints within the cell cycle ensure that cells do not continue to proliferate unchecked. These mechanisms collectively ensure that once healing is near completion, the balance between cell proliferation, differentiation, and death is maintained, restoring tissue homeostasis and preventing abnormal growths. **In summary:** When healing is almost complete, the formerly rapidly dividing cells halt their division and either differentiate into their final cell types or undergo programmed cell death. This cessation of proliferation ensures that the tissue returns to its normal, stable state. When healing is nearly complete, the formerly rapidly dividing cells cease dividing and either differentiate into their final cell types or undergo programmed cell death, stopping their proliferation as tissue repair finishes.