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why humans can grow adult teeth, and knee caps, as well as repair broken/fractured bones, but can’t regrow them if they get removed?

Dr. Aris Thorne
Dr. Aris Thorne
Senior Science Editor · Jan 13, 2026 · Updated Apr 13, 2026

Both teeth and knee caps are things that we are born with. Specifically, if you didn't know, we are actually born with all our adult teeth. When they "grow" in they're actually just shifting out from their little storage zones in our skulls – there are plenty of kinda spooky pics on google showin…

130
Words

1 min
Read Time

#52
of 500 in Human Body

+88%
vs Category Avg

The Short Answer

Both teeth and knee caps are things that we are born with. Specifically, if you didn't know, we are actually born with all our adult teeth. When they "grow" in they're actually just shifting out from their little storage zones in our skulls – there are plenty of kinda spooky pics on google showing both baby and adult teeth in xrays/skulls (RIP) of kids. Basically, the simple ELI5 answer is that the various parts of our bodies have the instructions for growing them stored in their genes. So our fingers know how to grow more finger-meat, our leg bones know how to grow more leg-bone, etc. But if the entire thing is removed, then the instructions are gone. So our body can't figure out how to grow it back.

Analysis

Key Concepts: Grow, teeth, know

This explanation focuses on grow, teeth, know and spans 130 words across 7 sentences. At 88% above the average Human Body explanation (69 words), this is one of the more thorough answers in this category, reflecting the complexity of the underlying question.

What This Answer Covers

The explanation opens with: “Both teeth and knee caps are things that we are born with.” It then elaborates by presenting a contrasting perspective, ultimately building toward a complete picture across 7 connected points.

How This Compares in Human Body

Ranked #52 of 500 Human Body questions by answer depth (top 11%). This places it in the comprehensive tier — the top quarter of most thoroughly answered questions. Questions at this depth typically involve multi-faceted topics requiring nuanced explanation.

Frequently Asked Questions

Is there a simple explanation for why why humans can grow adult teeth, and knee caps, as well as repair broken/fractured bones, but can't regrow them if they get removed?

Both teeth and knee caps are things that we are born with. Specifically, if you didn't know, we are actually born with all our adult teeth. When they "grow" in they're actually just shifting out from their little storage zones in our skulls – there…

How detailed is this explanation compared to similar Human Body questions?

This is one of the most thorough answer at 130 words, ranked #52 of 500 Human Body questions by depth. The key concepts covered are grow, teeth, know.

What approach does this answer take to explain why humans can grow adult teeth, and knee caps, as well as r?

The explanation uses contrasting perspectives across 130 words. It is categorized under Human Body and addresses the question through 1 analytical lens.