From birth to adulthood, what happens to the total number of bones?

• A. It increases as cartilage turns into bone
• B. It decreases because bones fuse over time
• C. It remains constant after birth
• D. It fluctuates seasonally

Answer: (B)

From birth to adulthood, the total number of bones decreases because many bones that start as separate elements fuse together as you grow. At birth you have roughly 270 bones, many of which are cartilage or separate centers of ossification. As development proceeds, those bones merge or fuse, especially in the skull, spine (sacrum and coccyx form from fused vertebrae), and other regions, so the adult skeleton typically has about 206 bones. Growth involves bones becoming larger and stronger, not simply adding more separate bones, so the overall count goes down rather than up. It isn’t constant after birth, and it doesn’t fluctuate with seasons, which is why that option doesn’t fit.