Lesson 1
Tiny cells, huge power
A planarian is a small flatworm that glides along the bottom of ponds and streams. It has a triangle-shaped head with two eyespots.
Neoblasts are spread all through the worm's body. They are small and round, with a big nucleus and only a little bit of cell around it.
Neoblasts are stem cells. A stem cell can split to make new cells, and those new cells can become many different kinds: skin, muscle, gut, even brain and eyes.
Try thisScroll up to the 3D model and press Regrow the worm.
Lesson 2
Rebuilding a whole worm
When a planarian is cut, neoblasts near the cut start splitting. They gather at the wound and make a little bump of new cells. That bump grows into whatever part is missing, like a head or a tail.
In about a week or two, the piece becomes a whole little worm again. Neoblasts also replace old cells every day, so the worm stays healthy.
You have stem cells too, in places like your bone marrow and skin. They help heal cuts and make new blood cells, but they can't regrow a whole body.
Wow!Scientists put just one special neoblast into a worm that had lost all its own neoblasts. That single cell grew and rebuilt the worm's whole supply of new cells!