virtsanjohdinta

Virtsanjohdinta, also known as the ureter, is a muscular tube that carries urine from the kidney to the bladder. Humans have two ureters, one extending from each kidney. These tubes are approximately 25 to 30 centimeters long and about 5 millimeters in diameter. The ureters are lined with transitional epithelium, which can stretch to accommodate the flow of urine.

The wall of the ureter consists of three layers: an inner mucous membrane, a middle muscular layer, and an outer adventitia. The muscular layer is responsible for peristalsis, a wave-like muscular contraction that propels urine down the ureter towards the bladder, even against gravity. This process is crucial for efficient urine transport.

Urine enters the ureter from the renal pelvis, the funnel-shaped structure at the top of the ureter where it connects to the kidney. The ureters then pass through the abdominal cavity and pelvic cavity, entering the bladder obliquely through the posterior wall. This oblique entry creates a flap-like valve that prevents the backflow of urine from the bladder into the ureters, a condition known as vesicoureteral reflux.

Problems with the ureters can arise, such as obstruction caused by kidney stones or strictures, which can impede urine flow and lead to pain and kidney damage. Infections can also affect the ureters, sometimes spreading from the kidneys or the bladder. Medical conditions like ureteropelvic junction obstruction, where the ureter is blocked at its connection to the kidney, can also require treatment.