<P> Cardiac muscle is also formed through myogenesis but instead of recruiting stem cells to fuse and form new cells, heart muscle cells--known as cardiomyocytes--simply increase in size as the heart grows larger . Similarly to skeletal muscle, if cardiomyocytes had to continue dividing to add muscle tissue the contractile structures necessary for heart function would be disrupted . </P> <P> Of the four major types of bone cells, osteocytes are the most common and also exist in a terminal G phase . Osteocytes arise from osteoblasts that are trapped within a self - secreted matrix . While osteocytes also have reduced synthetic activity, they still serve bone functions besides generating structure . Osteocytes work through various mechanosensory mechanisms to assist in the routine turnover over bony matrix . </P> <P> Outside of a few neurogenic niches in the brain, most neurons are fully differentiated and reside in a terminal G phase . These fully differentiated neurons form synapses where electrical signals are transmitted by axons to the dendrites of nearby neurons . In this G state, neurons continue functioning until senescence or apoptosis . </P>

When do nondividing cells exit the cell cycle