The Fetal Skeleton

"Your eyes saw my unformed body; all the days ordained for me were written in your book before one of them came to be."
                                             ~ Psalm 139:16

The adult skeleton consists of 210 bones, but a newborn baby has closer to 275 bones. This is because many adult bones (such as the sternum and the phalanges) originally start out as several pieces that fuse later in life. 

          The fetal skeleton differs from the adult skeleton in other ways, as well. The skull of the fetus is disproportionately large, as is the ribcage. The limbs, on the other hand, are disproportionately short.  The wrist and ankle bones are small and mostly cartilage. The mandible is almost straight, and this undoubtedly makes nursing easier for the mother since the amount of leverage produced by the baby’s jaw is dramatically reduced.

          The skull bones of the fetus are not fused, but they are held loosely together by connective tissues called fontanels. This design feature allows the skull (the widest part of the fetus) to be compressed and distorted during the birthing process. This is often necessary to allow successful passage through the narrow birth canal. Fontanels persist for several months after birth and are often referred to as “soft spots.”

SF-1-fetal skeleton.jpg
SF-2-fetal skull.jpg