Is the urethra part of urinary system?

Yes, the urethra is part of the urinary system.

The urethra is a tube that carries urine from the bladder to the outside of the body. It is part of the lower urinary tract, which also includes the kidneys, ureters, and bladder. The urethra is lined with mucous membranes and contains muscles that help to control the flow of urine. In males, the urethra also carries semen from the testicles to the outside of the body.