Eli5 how some lizards drop their tails at will without blood loss. What happens biologically to enable this?

Question

I’ve googled but the mechanism of the detachment is unclear.

In: 3

Answer 1

So the muscles in the tail have a plate that lets it slip out of contact with the rest of the spinal column.

This is called a fracture plane.

The muscles along the fracture plane will separate allowing it to come off. This fracture plane stops blood vessels from bleeding out. It’s a hard analogy to understand I get it. The blood vessels in the tail know to close themselves off from evolutionary pressure. If they didn’t they would bleed out and die leading to a unsuccessful evolution. Those who bled out died didn’t reproduce.

Some squirrels can lose their tails and never grow them back again. Reptiles are unique in that some can regrow their tails.