Like, 94 more!
Babies really have their work cut out in the growth department, including the formation of hundreds of bones. You heard that right—HUNDREDS! Us tiny humans are born with more than 300 bones, yet by the time we reach adulthood, we only have 206…so what the heck happens to those extra 94 bones?! Let’s back up to the beginning.
While in utero, somewhere between 9-12 weeks of pregnancy, a baby’s muscles and bones start to grow (1). Most of those bones are made of cartilage at first, much like the tip of your nose. Touch the tip of your nose. Go on, touch it! That’s how soft your bones were at first! Over time as a baby continues to gestate, the bones start to harden…but not too much. They need to stay flexible enough (especially the skull!) to make it through the tight squeeze of the birth canal (1).
Every see a newborn with a “cone head” (see below- almost all babies born vaginally have a misshapen head at first!)
This is a demonstration of just how flexi those bones need to remain in order for us to be born. At birth our skulls alone have 7 distinct bones, each connected by fibrous tissue. These connectors, called cranial sutures, typically don’t fuse until the age of 2. Why? To allow time for our big ole brains to grow (2). By the time we’re 2 years old, our brain reaches 75% of its adult size—tripling in size from the time of birth when it was approximately 25% of its adult size (3). Talk about mind blown! (pun intended!) Also, if our skull bones were fused together from the start, it would be WAY hard (read, impossible) for us to fit through the vaginal canal.
And that’s not all there is to the number of baby’s bones. Starting our lives with so many soft bones, with so much cartilage, is actually what enables our skeleton to grow. And grow it does…all the way through around our mid-20s!
What happens? Well, very simply put, throughout infancy, childhood and adolescence our bodies are constantly replacing that cartilage with new bone tissue (and collagen, calcium, proteins, an “organic glue” of sorts, and then inorganic salts so that they harden) to help our skeletons grow in size and density. This process is called ossification and in the end, it actually decreases the total number of bones we end up with because they start to fuse together as the cartilage is replaced (bigger, but fewer bones!) (4). While ossification starts in-utero, it doesn’t end until our mid to late twenties (whoa!) at which point the total amount of bone tissue in our body, a.k.a. bone mass, peaks and our skeleton reaches it’s final size.
Written by: Amanda Hayden, LMSW, CBC, full spectrum doula