[CentOS] mysql.users deleting

Hello,

Today I was working with MySQL in a test box (CentOS 5.0 x86_64) using 
phpMyAdmin interface. Accidentaly I've removed user table in mysql 
database (so, mysql.users)...

:S

I've two interesting questions:

1) Despite of it, ddbb server seems to work perfectly. I use 3/4 
diferent databases with their mysql users... and it works yet! I don't 
understand, because mysql.users is the reference that MySQL server uses 
to admin their users and permissions access.

¿?¿?¿?¿?¿ Maybe a kind of memory caché is active... but I think this 
have not any sense...

I've suposed the mysql.user was totally _required_.

2) ¿How I can reisert mysql.user table without reinstall entire package?
I've got only a few mysql users only and I can recreate their 
permissions access in short time.

-- 
Thanks,
Jordi Espasa Clofent