Final answer:
The trigone of the urinary bladder is formed by the two ureteral openings at the posterior-lateral aspect and the urethral orifice at the anterior aspect, creating a triangular shape at the bladder's base.
Step-by-step explanation:
The trigone of the urinary bladder is created by the two ureters entering the bladder at the posterior-lateral aspect and the urethral orifice located in the anterior aspect. These three points form a triangular-shaped area at the base of the bladder. The urethra, which begins inferior and central to the two ureteral openings, is responsibility for transporting urine from the trigone to outside the body.
The bladder and ureters work together to ensure the proper flow and storage of urine. Urine formed in the kidneys travels down the ureters, which are lined with smooth muscle that contracts in a peristaltic motion to help move the urine toward the bladder. Within the bladder, urine collects until it is expelled during urination, controlled by both involuntary and voluntary sphincters.