What acts as a filter in peritoneal dialysis?

In peritoneal dialysis, the lining of the abdomen, known as the peritoneum, acts as the filter. The peritoneum is a thin membrane that surrounds the abdominal organs and contains numerous blood vessels. When dialysate is introduced into the peritoneal cavity, substances like waste products and excess fluids can pass through the peritoneal membrane into the dialysate, while larger molecules such as blood cells and proteins typically remain in the bloodstream. This selective filtration process allows for effective removal of toxins and excess substances from the blood, mimicking the natural filtering action of healthy kidneys.

The other choices do not serve as the filtering mechanism in peritoneal dialysis. The dialyzer membrane is relevant in hemodialysis, where it filters blood outside of the body, while blood cells and catheter tubing are components involved in the dialysis process but do not have the filtering capacity of the peritoneum.