[Verse 1]
Your skeleton's not chalk, it's not some dusty old stone,
It's living tissue, breathing, growing, calling itself home.
Sixty percent mineral, a crystal called hydroxyapatite,
Twenty-some percent collagen, braided ropes holding tight,
The rest is water, quiet, filling in the seams,
Built like rebar sunk in concrete, that's the bone-and-mortar scheme.
Collagen bends so you don't shatter at a jog,
Mineral hardens so you don't fold like a wet log.
[Chorus]
Stone and thread and water, that's the recipe inside,
Sixty, thirty, ten, let that ratio be your guide.
Rebar in the concrete, flexible yet strong,
Crystal plus the collagen, that's the skeleton's whole song.
[Verse 2]
Crack one open, you'll find two different kinds of ground,
Cortical is compact, the dense shell wrapping all around,
But inside the ends of your limbs, your spine's each vertebra,
Trabeculae crisscross like tiny beams of scaffold-bar,
A honeycomb of struts, osseous lattice, light and sly,
Spongy bone they call it, built for weight without the size.
[Chorus]
Stone and thread and water, that's the recipe inside,
Sixty, thirty, ten, let that ratio be your guide.
Rebar in the concrete, flexible yet strong,
Crystal plus the collagen, that's the skeleton's whole song.
[Verse 3]
Wrap the bone in periosteum, its nervy outer skin,
That's exactly why a fracture makes you wince and the room spin,
Every nerve lives in that wrapper, not the mineral core,
Snap the shell and suddenly your senses slam the door.
Deep inside, the endosteum lines the marrow's hollow hall,
Quiet, thinner, tending to the cavity and wall.
[Verse 4]
Marrow comes in colors like a secret double shift,
Red marrow's the factory, churning blood cells, no days off, no gift,
Yellow marrow's lazier, just storing fat and rest,
Grown-ups keep their red marrow where the flat bones serve it best,
Pelvis, sternum, skull bones, humming engines, low and deep,
While the long bone shafts go yellow, fatty, fast asleep.
[Verse 5]
Osteoclasts dig in, breaking old bone away,
Osteoblasts build it back up, layer by layer each day,
A living renovation, cycling strong and slow,
That's how a skeleton rebuilds the strength you'll ever know,
Ten percent of your frame gets replaced inside a year,
Proof that this stone-and-thread machine is always, always near.
[Bridge]
So when the stone fatigues, or the collagen gives way,
That's the fracture story we'll unravel on another day,
Healing means rebuilding both the crystal and the thread,
Same ingredients returning, stitching bone instead of dread.
[Outro]
Stone and thread and water, sixty, thirty, ten,
Rebar wrapped in concrete, growing, breaking, healing again,
Cortical the armor, trabecular the lace,
Periosteum's the feeling, marrow's the red and yellow place.