Final answer:
The bones stop growing at approximately 18 years for females and 21 years for males due to epiphyseal plate closure. While bone length growth ceases post-adolescence, bone thickness can still increase in response to physical activity. Peak bone mass is achieved in the thirties, after which it tends to decrease, with females experiencing a more rapid decline post-menopause.
Step-by-step explanation:
In both males and females, the bones stop growing and reach maturity through a process known as epiphyseal plate closure. This usually occurs at the age of about 18 for females and around 21 for males. The cartilage cells within the epiphyseal plate (growth plate) cease to divide, and eventually, all the cartilage is replaced by bone, marking the end of longitudinal bone growth. This leads to the formation of the epiphyseal line or remnant as the epiphysis (end of the bone) and diaphysis (shaft of the bone) fuse. Post-skeletal maturity, bones can still increase in thickness in response to factors such as weight training or muscle activity.
Furthermore, during adolescence, males tend to experience a greater increase in muscle and bone growth compared to females, which contributes to the differences in body composition and shape between the sexes. Adolescent growth spurt timings also differ, with females typically beginning and completing the process earlier than males.
Bone mass reaches its peak in both sexes in their thirties. Afterward, bone mass generally declines, with this reduction occurring more rapidly in individuals with XX chromosomes, particularly after menopause due to lower levels of estrogen. Therefore, osteoporosis is more prevalent in females, although males can also be affected by this condition.