How does urine travel from the kidneys to outside the body?

After urine is formed in the kidneys, it travels through a specific pathway to be excreted from the body:

• Renal Pelvis: Urine collects in the renal pelvis, the upper expanded portion of the ureter.12
• Ureters: Peristaltic waves of contraction move urine down the ureters—narrow, thick-walled ducts—into the urinary bladder. The ureters enter the bladder wall at an oblique angle, which acts as a valve to prevent urine from flowing backward toward the kidneys.134
• Bladder: The bladder serves as a storage reservoir. As it fills, internal pressure rises until the detrusor muscle contracts and the bladder neck relaxes to initiate urination.56
• Urethra: The urethra is the final channel that conveys urine from the bladder to the exterior of the body. The process of voiding is controlled by both involuntary reflexes and voluntary muscle actions.7258