Which blood vessel contains the least amount of urea?

Given below are two statements:
Statement $I$: At the base of the urinary bladder,there is an inverted triangular area called the trigone.
Statement $II$: Three layers of dartos tunic muscles are present in the wall of the urinary bladder.
In the light of the above two statements,choose the correct option.

Renal pyramids are parts of the ...... .

In which of the following is the minimum content of urea present?

The main function of the renal pyramids of the kidney is to:

Describe the structure of a human kidney with the help of a labelled diagram.