The Last Supper(Jesus' last big dinner)

it is 'The Last Supper', drawn by Leonardo da Vinci(or not) this represents the last supper that was in  Luke of Bible. Jesus said, "the bread shall be my piece, and the wine is my blood."
but question, why is the piece and blood being drank?
this is very strange. why does he want his blood to be drank? and further more, its painful! if someone's blood is drank, meaning, the person is heavily wounded! the last supper is one of the famous works by various artists, but i really don't get it!

da vinci sempre!
viva gilda dell'assassino!(-by Ezio Auditore)