The skeleton of a newborn infant contains around 300 separate parts, according to the BBC. All bones start out as cartilage and turn into bone through a process known as ossification. This process is usually still underway at birth, so an infant skeleton is composed of both bone and cartilage.
During ossification, many infant bones fuse together to form larger or longer bones. At the end of the process the human body contains a total of 206 bones. The femur, also known as the thigh bone, is the longest with an average length of 20 inches. The smallest bones are found in the inner ear.