BrainStuff Classics: How Do Our Bones Grow?

We humans are fairly squishy, and we eat fairly squishy food. So how do we grow hard bones? Learn how it happens in this classic episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio. Hey Brainstuff, Lauren
bogel Bomb here with another classic from our archives. If
you're anything like me, you went through a phase or
are still in a phase where you've been fascinated by
the idea that you've got a skeleton living inside you
all the time. So in this episode we talked about

(00:25):
how our bones grow. Hey brain Stuff, Lauren Bogelbomb here.
We all know that you are what you eat, but
how exactly do the things that you eat get turned
into pieces of you? I'm thinking of bones in particular here.
The foods we humans consume are soft, especially compared to
other animals diets, but from them our bodies build strong,

(00:46):
hard materials like fingernails, tooth enamel, and bones. So how
do we do it? How do we soft fleshy humans
turn soft fleshy food into bones. Let's start off by
zooming in all the way down to the cellular level.
Your body builds bone tissue with the help of specialized
cells called osteoblasts. Osteoblasts work together forming a tight fit

(01:08):
layer over areas where bone needs to grow or be repaired.
These cells secrete a particular combination of amino acids, primarily
glycine and proleine. These amino acids are the building blocks
of proteins. Not unlike voltron, they fold up with each
other into something more than the some of their parts,
though in this case it's not a space faring super robot,
but strong triple helix threads of protein. Your cells get

(01:32):
these amino acids from the foods that you eat. Meat, fish, dairy,
and lagumes contain both glycine and proline, and you can
also get proline from stuff like gelatine and cabbage. Once
your osteoblasts secrete the immuno acids and they come together
to form the protein threads, enzymes give those threads a
stabilizing polish. Vitamin C helps those enzymes work. Without it,

(01:53):
the threads can't come together to form bone tissue correctly.
That's what happens in scurvy, and it's one of the
reasons why you should eat some fruit sometimes. Cantelope, citrus, kiwi, mango,
and berries are all good sources. The thus stabilized threads
are molecules of what's called collagen, which is the most
abundant protein in the animal kingdom. Collogen molecules pack together

(02:13):
into long, thin fibers called fibrils. In there many types
fibrals create these scaffolding that bodily tissues are built upon,
from your corneas to your blood vessels to your skin.
They're sturdy and kind of flexible, like steel beams in architecture.
They're also relatively light weight. Adult human bones are about
ten percent collagen by mass, but if your bones were

(02:35):
collagen fibrils alone, you'd beat sentient silly putty. So to
add further support, your osteoblasts guide deposits of a strengthening
layer of mineral crystals along the fibrils, like pouring concrete
over steel beams. The mineral in question here is the
compound calcium phosphate. Calcium and phosphate bond in your system
after you consume foods that contain them. For calcium, that's

(02:57):
dairy and soy products, eggs, sh and dark leafy greens.
For phosphate, it's dairy, whole wheat, nuts, and lagumes. And this,
along with dairy's amino acid content, is why milk and
fortified food ads talk about how these products help build
strong bones, though of course all the other foods we've
mentioned do too, This mineral coating is just a few

(03:18):
atoms thick, but it gives bones their stiff structure, and
it accounts for about sixty five percent of adults bone mass. Finally,
the coated fibrils get gummed together with a sort of
shock absorbing glue made up of spiraled collagen molecules that
can uncoil when stress is applied and then snap back
into shape. This helps prevent fractures at a molecular level.

(03:40):
If you connected your steel reinforced concrete beams with springs,
your skeleton also contains small amounts of magnesium, sodium, and bicarbonate,
plus a bunch of water, like twenty five percent by mass.
So how does your body get a hold of all
of these substances. Well, your digestive system is a fancy
molecular ar blaster. When you eat your teeth, gastrointestinal muscles

(04:03):
and digestive juices break food down to the point that
it's molecules already to be harvested. Your gut bacteria helped too.
There are some molecules that our cells can't process by themselves.
Our gut bacteria eat those molecules and poop out compounds
that our cells can process. The cells in the walls
of your small intestine pass everything that they can into
your bloodstream to be carried on to maker cells like

(04:26):
your osteoblasts. Today's episode is based on a videoscript that
I wrote for Houstoffworks dot Com. Brainstuff is production of
iHeartRadio in partnership with Houstoffworks dot Com, and it's produced
by Tyler Clang. Four more podcasts from my heart Radio.
Visit the iHeartRadio app, Apple Podcasts, or wherever you listen

(04:46):
to your favorite shows.