B12.4 Dialysis - an artificial kidney

Question 1

What are the 2 methods of treating kidney faliure?

Answer 1

Dialysis

Kidney transplant

Question 2

What is dialysis?

Answer 2

Function of the kidney is carried out artificially

Relies on the process of dialysis to clean the blood

Question 3

What happens in a dialysis machine?

Answer 3

A person’s blood leaves their body and flows between partially permeable membranes

On the other side of the membrane is the dialysis fluid - fluid contains the same concentration of useful substances as the blood of a healthy person

Question 4

What are the problems with dialysis?

Answer 4

Takes 8 hours for it to complete
Have to manage diet carefully
Helps keep their blood chemistry as stable as possible so that they can lead a normal life between sessions

Question 5

How does dialysis work?

Answer 5

Dialysis fluid removes the harmful substances

Question 6

What is the importance of the dialysis fluid?

Answer 6

Contains the same concentration of glucose and mineral ions as blood of a person without kidney disease - ensure no net movement of glucose out of the blood

Question 7

Why does the dialysis fluid contain a normal plasma level?

Answer 7

Any excess ions are removed from the bloody by diffusion from the blood into the dialysis fluid by a concentration gradient

Question 8

What is the importance of the fluid containing no urea?

Answer 8

Makes a steep concentration gradient - much of the urea leaves the blood

Question 9

Why is a partially permeable surface important?

Answer 9

This membrane allows particles that the body needs to get rid of to pass through it, but doesn’t let important parts of the blood (e.g. blood cells) pass through

Question 10

What are the problems of dialysis?

Answer 10

Have to spend regular long sessions connected to it and you may feel tired
Balance of substances can be difficult to control

Question 11

Why does the blood go through a bubble trap?

Answer 11

To get rid of any bubbles

Question 12

What is the overall view of how a dialysis machine works?

Answer 12

• Blood passes out of artery via pump.
• Blood thinners added to prevent clotting.
• Blood passes between dialysis membranes where excess salt and urea are removed by diffusion down a concentration gradient.
• Clean blood passes through bubble trap before returning to vein.

Question 13

What is the purpose of blood thinners?

Answer 13

Prevent clotting

Question 14

Why do people with kidney failure have to control their intake of protein and salt?

Answer 14

• People with kidney failure cannot remove excess mineral ions such as salt or get rid of urea produced by the breakdown of excess amino acids from proteins.
• So they have to limit intake to keep levels in body as low as possible to remain feeling well between dialysis sessions.

Question 15

Why is it important for the blood and dialysis fluid to be circulated?

Answer 15

To help maintain optimum concentration gradients.
Dialysis process relies on diffusion down concentration gradients (no
active transport), maintained by flow of fluid.