State in brief the function of:
$(a)$ Renal artery
$(b)$ Kidney
$(c)$ Ureter
$(d)$ Urinary bladder

(N/A) Renal artery: It carries oxygenated blood containing nitrogenous wastes from the aorta to the kidney for filtration.
$(b)$ Kidney: It is the primary excretory organ that filters the blood to remove metabolic wastes,excess water,and salts,thereby forming urine.
$(c)$ Ureter: It is a pair of thin muscular tubes that transport urine from the kidneys to the urinary bladder.
$(d)$ Urinary bladder: It is a muscular sac that stores urine temporarily until it is voided from the body through the urethra.