you're born with 300 bones, but when you get to be an adult, you only have 206!
The
human skeleton begins to develop 13 to 16 weeks after conception. At
birth, a human has about 300 bones and cartilage elements, and many
bones that will eventually fuse together are still separate, although
joined by tough membranes. The malleable nature of cartilage allows for a
baby’s easier passage through the birth canal.
As an adult, the skull consists of 26
cranial and facial bones fused together along unmovable joints called
sutures, with the exception of the mandible, or jaw, which is attached
at a moveable joint. At birth, many of those bones are not yet fused and
instead are joined by fibrous membranes called fontanelles. The
fontanelles are the so-called “soft spot” on an infant’s head.
Eventually the fontanelles close as the bones grow together.
The process of changing cartilage to bone is
called ossification, and begins before birth and continues into a
person’s 20s. Ossification occurs when capillaries bring blood to
bone-forming cells called osteoblasts. The osteoblasts then begin
producing compact bone, covering the cartilage and eventually replacing
it.
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