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Question Video: Recalling the Process by Which Waste Products Move Out of the Blood and into the Dialyzate Biology

During dialysis, what process is involved in the movement of waste substances out of the blood and into the dialysis fluid?

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Video Transcript

During dialysis, what process is involved in the movement of waste substances out of the blood and into the dialysis fluid? (A) Translocation, (B) transpiration, (C) diffusion, or (D) active transport.

If a person is suffering from kidney failure, they may be offered dialysis. The main aim of dialysis is to replace the function of the kidneys. Our kidneys are essential in removing waste products, like urea, from our blood. If a person’s kidneys start to fail, they often experience a buildup of waste products in their blood. Let’s have a closer look at how dialysis works in removing these waste products from a person’s blood.

During dialysis, the patient is connected to a dialyzer. Blood is removed from the patient’s arm via an artery, passed through pressure monitors and blood pumps, before being moved into the dialyzer itself. The dialyzer has a constant supply of fluid called dialysate. In the dialyzer, waste products in the blood that have built up as a result of the kidneys not functioning properly move from the blood and into the dialysate. So by the time the blood then reenters the patient’s arm, it is clean.

In the blood that enters the dialyzer, there is a high concentration of waste products. In the dialysate, however, there is a very low concentration of waste products. Therefore, the waste products move from an area of high concentration to an area of low concentration.

We know that diffusion is the passive movement of molecules down their concentration gradient, from an area of high concentration to an area of low concentration. So our correct answer must be (C). The process involved in the movement of waste substances out of the blood and into the dialysis fluid is diffusion.

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