Final answer:
The growth of smooth muscle in the uterus through cell division and enlargement is due to hyperplasia, influenced by increased estrogen levels and the activity of stem cells called pericytes.
Step-by-step explanation:
The ability of smooth muscle to undergo cell division and grow, particularly in the uterus, is due to a process called hyperplasia. This is observed at puberty when the uterus responds to increased estrogen levels, resulting in the production of additional uterine smooth muscle fibers and significant growth of the myometrium. Unlike skeletal and cardiac muscles, which mainly grow through hypertrophy, or increase in size of existing cells, smooth muscle can also regenerate and increase the number of cells through hyperplasia and the activity of stem cells known as pericytes.