Here's a breakdown:

* Production: Urea is produced in the liver as a byproduct of protein metabolism.

* Transportation: It is then transported through the bloodstream to the kidneys.

* Filtration: The kidneys filter the blood, removing waste products like urea.

* Concentration: The kidneys concentrate the urea and other waste products into urine.

* Excretion: The urine is then excreted from the body.

So, while urea is initially formed in the liver, it is the kidneys that are responsible for concentrating it from the blood and removing it from the body.