URETERS, URINARY BLADDER, AND URETHRA

The ureter is a muscular tube that transports urine to the urinary bladder. The smooth muscle of the ureter helps in this transport process as it undergoes peristaltic waves of contraction that stimulate the flow of urine to the urinary bladder. Each ureter originates at the renal pelvis (or the major calices of the bovine kidney) and empties into the urinary bladder near its neck at the trigone. The backflow of urine to the kidney is prevented by a type of valve in the ureter. The urinary bladder is a muscular organ that var­ies in size with the amount of urine it contains. The pelvis, ureter, bladder, and urethra are all lined with transitional epithelium. This epithelial lining is useful in these areas, since considerable distension of the lumen may occur.

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