The Kidneys

Question 1

1. Very simply, what do the kidneys do?

Answer 1

1. The kidneys basically act as filters to clean the blood.

Question 2

What is the kidneys function?

Answer 2

1. The kidneys make urine by removing waste products from your blood.
2. Substances are filtered out of the blood as it passes through the kidneys. This process is called filtration.
3. Useful substances like glucose, some ions and the right amount of water are then absorbed back into the blood.
4. This processes is called selective reabsorption.

Question 3

What substances are removed from the blood?

Answer 3

1. Urea
2. Some ions
3. Some water

Question 4

Urea and filtration?

Answer 4

1. Proteins and their amino acids can’t be stored by the body - so any excess amino acids are converted into fats and carbohydrates, which can be stored.
2. This occurs in the liver and involves a process called deamination.
3. Ammonia is produced as a waste product from this process.
4. Ammonia is toxic, so it is converted into urea in the liver. Urea is then transported to the kidneys, where it is filtered out of the blood and excreted from the body in urine.

Question 5

Ions and filtration?

Answer 5

1. Ions such as sodium are taken into the body in food, and then absorbed into the blood.
2. If the ion content of the body is wrong, this could upset the balance between ions and water, meaning too much or too little water is drawn into cells by osmosis.
3. Having the wrong amount of water can damage cells or mean they don’t work as well as normal.
4. Some ions are lost in sweat. However, this amount is not regulated, so the right balance of ions in the body must be maintained by the kidneys. The right amount of ions is reabsorbed into the blood after filtration and the rest is removed from the body in urine.

Question 6

Water and filtration?

Answer 6

1. The body has to constantly balance the water coming in against the water going out.
2. We lose water from the skin in sweat and from the lungs when breathing out.
3. We can’t control how much we lose in those ways, so the amount of water is balanced by the amount we consume and the amount removed by the kidneys in urine.

Question 7

How is the concentration of urine controlled?

Answer 7

1. The concentration of urine is controlled by a hormone called anti-diuretic hormone (ADH). This is released into the bloodstream by the pituitary gland.
2. The brain monitors the water content of the blood and instructs the pituitary to release ADH into the blood according to how much is needed.
3. This whole process is controlled by negative feedback.

Question 8

What happens if the kidneys don’t work properly?

Answer 8

1. If the kidneys don’t work properly waste products build up in the blood and you lose your ability to control the levels of ions and water in your body. Eventually, this results in death.

Question 9

How can people who have kidney failure be helped?

Answer 9

1. People with kidney failure can be kept alive by having dialysis treatment where machines do the job of the kidneys.
2. They could have a kidney transplant.

Question 10

How does dialysis work?

Answer 10

1. Dialysis has to be done regularly to keep the concentrations of dissolved substances in the blood at normal levels, and to remove waste substances.
2. In a dialysis machine, the person’s blood flows between partially permeable membranes, surrounded by dialysis fluid. It’s permeable to things like ions and waste sunstances, but not big molecules like proteins (just like the membranes from the kidney)
3. The dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood.
4. This means that useful dissolved ions and glucose won’t be lost from the blood during dialysis.
5. Only waste substances and excess ions and water diffuse across the barrier.

Question 11

Disadvantages of dialysis?

Answer 11

1. Many patients with kidney failure have to have a dialyis session 3 times a week, and each session takes 3-4 hours.
2. Dialysis may cause blood clots or infections.
3. Being on a dialysis machine is not pleasant, and it is expensive for the NHS to run.

Question 12

How do kidney transplants work?

Answer 12

1. At the moment, kidney transplants are the only cure for kidney failure.
2. Healthy kidneys are usually transplanted from people who have died suddenly.
3. The person who died has to be on the organ donor register or carry a donor card.
4. Kidneys can also be transplanted from people who are still alive but there is a small risk to the person donating the kidney.

Question 13

Disadvantages of kidney transplants?

Answer 13

1. There is a risk the donor kidney can be rejected by the patient’s immune system.
2. The antigens on the cell surface of the donor organ can trigger the your antibodies oin the immune system to attack the foreign antigens.
3. The patient is treated with immunosuppressants to prevent this.

Question 14

Compare dialysis and kidney transplant?

Answer 14

1. Transplants are cheaper in the long run than dialysis, and people with a kidney transplant can live a more free life.