The kidney and the urinary system

The diagram shows a nephron from a human kidney with some structures labelled.

Which of these is structure U?

Which process occurs between structure S and structure T?

Which structure is the collecting duct?

The table shows the concentrations of protein and glucose in blood plasma, in glomerular filtrate and in urine.

Calculate the mass of glucose in 5 dm³ of blood plasma.

[1000 cm³ = 1 dm³]

Explain why there is no protein in the urine.

Explain why there is glucose in the glomerular filtrate but no glucose in the urine.

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow. Kidney transplants The main role of the kidneys is to filter waste products from the blood. If the kidneys lose this ability, waste products can build up, which could lead to death. This loss of kidney function, known as kidney failure, is the most common reason for needing a kidney transplant. It is possible to use a kidney machine to partially perform the functions of the kidney, using a blood filtering procedure known as dialysis. However, this can be inconvenient and it takes a long time. A kidney transplant is a better solution for kidney failure whenever possible. A kidney transplant is suitable for people of all ages who need to have one, if they are fit enough for surgery. If a patient has an infection this will need to be cured before the transplant. The person who receives the transplant must agree to continue with the recommended treatments after the transplant. These treatments include taking medication known as immunosuppressant drugs. People have two kidneys, but they can survive well with only one kidney. This means it is possible for a person to donate a kidney while they are alive. This is known as a living donation. People who want to be considered as a living donor are carefully tested to make sure they are a suitable donor and are fit for the operation needed to remove a kidney. Living donations are best from a close relative as this reduces the risk of the body rejecting the kidney. In the United Kingdom, the number of living donations in 2020 was 1040. In 2021 the number of living donations was 429. Kidney donations are also possible from people who have recently died. This is known as deceased kidney donation. However, this type of kidney donation has a slightly lower chance of long-term success. In the United Kingdom, the number of deceased donations in 2020 was 2283. In 2021 the number of deceased donations was 1836. People who need a kidney transplant, but do not have a suitable living donor, will have to wait until a suitable deceased donor kidney becomes available. In the United Kingdom, the average waiting time for a deceased donor kidney transplant is between 30 months and 36 months. Kidney donors are particularly required from people of non-white ethnic origin, as kidney disease is more common in people of South Asian, African and Afro‑Caribbean ethnic origin. However, there are not many donors from these communities.

When a person receives a kidney from a living donor, this is a carefully planned operation. If they are waiting for a deceased donor kidney, they will be contacted when a suitable kidney becomes available. The patient then has surgery to insert the new kidney and connect it to their blood vessels and bladder. The new kidney will be placed in the lower part of the abdomen. The patient’s own failed kidneys will usually be left in place.

State two waste products that kidneys remove from the blood. (Line 1)

Dialysis can be inconvenient and takes a long time. (Lines 6 and 7) Suggest two other reasons why a kidney transplant is a better solution for kidney failure than dialysis.

The patient receiving the transplant must take immunosuppressive drugs after the operation. These drugs reduce the action of the immune system. (Lines 12 and 13) Describe how the immune system responds to disease.

Explain why the chances of rejection are lower if the kidney comes from a close relative. (Lines 18 and 19)

The number of donations changed between 2020 and 2021. (Lines 20 and 21 and lines 25 and 26)

Calculate the difference between the percentage change in living donations from 2020 to 2021 and the percentage change in deceased donations from 2020 to 2021.

Suggest a reason why there are fewer transplant operations from living donors than from deceased donors.

Suggest what is meant by a suitable kidney. (Line 37)

Explain why kidney donors are particularly required from people of South Asian, African and Afro-Caribbean ethnic origin. (Lines 32 to 34)

Mammals, such as humans, need to regulate their internal environment.

What is the process that maintains a constant internal environment?

Table 1 shows the water input and output per day for a person in normal temperature conditions.

The water loss from gas exchange plus the loss from sweating are referred to as the insensible water loss. This water loss is called insensible because it cannot be measured directly.

Calculate the percentage of the water loss that is classified as insensible.

This data comes from a person who has a mass of 70 kg.

Assuming the same proportions, calculate the water input from food for a person who has a mass of 110 kg.

input from food =_........ litres

Water loss in faeces is usually relatively low.

Illness such as food poisoning can produce symptoms including vomiting, diarrhoea and a high temperature. These symptoms can change water balance in the body.

Explain how the symptoms of food poisoning can change water balance in the body.

The photograph shows a mammal called a degu.

(Source: © R. Maximiliane / Shutterstock)

A degu is a rodent that lives in a very dry environment in South America. The degu gets its water input by feeding on plants.

The water intake of the degu changes during the winter and summer months.

Table 2 shows the body mass, water intake and urine concentration of the degu in the winter and in the summer. It also shows the total rainfall in winter and in summer.

Comment on the differences in body mass, water intake and urine concentration in winter and summer.

Use the data in the table and your own knowledge in your answer.

Isotonic drinks are often used to rehydrate athletes after exercise.

Explain why athletes lose water during exercise.

Isotonic drinks contain salt and sugar solutions that are the same concentration as normal blood plasma.

A scientist uses this method to investigate how well an isotonic drink rehydrates athletes.

• three athletes exercise for one hour

• one athlete has no drink

• the second athlete drinks 1000 cm³ of pure water

• the third athlete drinks 1000 cm³ of isotonic drink

• the volume and colour of urine produced by each athlete are measured one hour later

The table shows the scientist’s results.

Explain the results shown in the table for the athlete who consumed no drink.

Explain the differences in urine volume and urine colour produced by the athlete who consumed the isotonic drink and the athlete who consumed pure water.

The diagram shows a nephron from a human kidney with some structures labelled.

Which structure is the Bowman’s capsule?

Which structure is the loop of Henle?

Which structure is affected by ADH?

Blood plasma contains much glucose, but urine normally does not. Explain what happens to glucose in the kidney.

Describe how a sample of urine could be tested for glucose.

As a person sweats, they may become dehydrated. Describe the changes in a person’s urine if they become dehydrated.

The diagram shows part of a human nephron.

Which structure is the proximal convoluted tubule?

The hollow space inside a blood vessel is called the lumen.

The blood vessel labelled X has a lumen with a radius of 100 μ m. Use this formula to calculate the cross‑sectional area, in mm², of the lumen of this blood vessel. area of circle = π ×(radius)² [ π = 3.14] [1 mm = 1000 μ m]

cross‑sectional area =_........

The lumen of blood vessel X is wider than the lumen of blood vessel Y. Explain why this difference in the width of the lumen of the two blood vessels is important for kidney function.

Protein is often found in the urine of people who have high blood pressure. Describe how urine could be tested for protein.

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Treating Kidney Disease

Chronic kidney disease affects approximately 12% of the world’s population and many people are unable to obtain treatment. One method of treating chronic kidney disease is by dialysis. The diagram shows how kidney dialysis is done.

During dialysis, blood is taken from an artery in the arm and is pumped through a dialyser. In the dialyser, the blood passes through a long, coiled dialysis tube made of a thin partially permeable membrane. The tube is surrounded by dialysis fluid. The dialysis fluid contains glucose and ions at concentrations normally found in blood plasma, but does not contain urea. The urea passes from the blood into the dialysis fluid. The temperature in the dialyser is kept at 40C. After passing through the dialyser, the blood is returned to a vein in the arm. Kidney dialysis can take up to three hours and must be done three times a week.

Scientists have now designed a new bioartificial kidney. This artificial kidney is a combination of engineering and living cells. This artificial kidney has a haemofilter made from artificial membranes that filter the blood. The substances filtered out of the blood then pass through a device called a bioreactor. This bioreactor absorbs useful substances back into the blood. The bioreactor is made of living nephron cells that are grown from stem cells. These cells are separated from the patient’s blood by a silicon membrane to prevent the immune system rejecting them. Bioartificial kidneys are the same size as a human kidney and will be fitted inside the body to replace a kidney. The bioartificial kidney can react to changes in the body in the same way as a normal kidney.

In 2021, the world’s population was 7 900 000 000.

Calculate the number of people in the world who have chronic kidney disease (Lines 1 and 2).

Give your answer in standard form.

Urea is an excretory product that is released by the kidneys.

Give the name of an excretory product that is released by the lungs.

Explain two ways that the dialyser is designed to increase the rate of removal of urea from the blood (Lines 5 to 11).

The haemofilter in the bioartificial kidney filters the blood (Lines 13 and 14).

Where does ultrafiltration occur in a nephron?

The cells in the bioreactor absorb glucose from the filtrate in a way that is similar to the cells in a nephron (Lines 14 to 17).

Describe how the nephron absorbs glucose back into the blood from the filtrate.

The bioartificial kidney is connected to blood vessels and to the tube that transports urine to the bladder in the same way as the human kidney.

Which row of the table is correct?

Explain how the pituitary gland and the nephron cells in the bioreactor will respond in a patient who is dehydrated (Lines 20 and 21).

The diagram shows a section through a human kidney with some structures labelled.

Which structure is labelled P in the diagram?

Which fluid is carried in tube S?

Which tube is labelled Q in the diagram?

Analysis of the composition of urine can be used in the diagnosis of problems with kidney function.

Urine samples are taken from three patients and the results are shown in the table.

Discuss which processes in the kidney may be affected to produce the results shown.

Include in your answer where in the nephron the processes occur.

Describe how to test for glucose in a sample of urine.

The diagram shows part of the human urinary system.

Name the structures labelled A and B.

The diagram shows a kidney nephron.

The table shows the relative concentrations of glucose and protein in the areas labelled X, Y and Z on the diagram.

Explain the difference between the concentration of protein in area X and the concentration of protein in area Y.

Explain the difference between the concentration of glucose in area Y and the concentration of glucose in area Z.

When the body becomes dehydrated, the concentration of urine increases.

Explain the changes that occur in the body that lead to the production of concentrated urine.

The diagram shows a nephron from a human kidney.

From which structure does ultrafiltration take place?

From which structure is glucose reabsorbed?

Which structure is the loop of Henle?

The table gives the mean values of mass filtered per day and excreted per day for different plasma components that are filtered and reabsorbed in the nephron.

State what is meant by plasma components.

Calculate the mean mass of urea excreted per day.

mean mass of urea =_........

Explain why glucose is reabsorbed in the nephron.

The concentration of urine is determined by the volume of water present and the mass of dissolved substances. A person eats a meal with a high protein and salt content and drinks a small volume of water. Comment on how this may change the values in the table and the effect it will have on urine production.

The diagram shows a nephron from a kidney with three different areas, X, Y and Z.

The table gives the concentration of glucose and urea at X, Y and Z.

Explain the difference in concentration of glucose between X and Y.

Calculate how many times more concentrated the urea is in area Z compared to area Y. Give your answer to two significant figures.

Explain the difference in urea concentration in the filtrate found in Y and Z.

High blood pressure during pregnancy can result in the production of urine that contains protein.

Describe how a sample of urine could be tested to see if it contains protein.

Protein is not normally found in urine. Suggest why high blood pressure could cause protein to be present in urine.

The urinary system is used in excretion.

The diagram shows the urinary system with parts labelled A, B, C and D.

Which part of the urinary system contains nephrons?

The urinary system produces urine.

Name a substance found in urine.

A scientist uses this method to investigate the effect of drinking different liquids on urine production.

• drink 600 cm³ of water in the morning

• measure the volume of urine produced during the next two hours

• drink 600 cm³ of 0.8 % salt (NaCl) solution at the same time the following morning

• measure the volume of urine produced during the next two hours

The table shows the scientist’s results.

Explain the scientist’s results.

Give two other factors that affect the volume of urine produced.

The human kidney is an organ that is able to process excretory products from human metabolism.

Concentration of urine is calculated using this formula.

The amount of waste the kidneys produce per day is 600 milliosmoles.

The maximum concentration that the human kidneys can produce is 1400 milliosmoles per dm³.

Calculate the minimum volume of urine that must be produced each day.

Give your answer in cm³.

Name another organ that carries out excretion in the human body.

Explain the role of the nephron in osmoregulation.

The diagram shows part of a human nephron, with parts labelled P, Q, R, S and T.

What is the name of part P?

Where does ultrafiltration occur?

Where is permeability affected by ADH?

Where is glucose selectively reabsorbed into the blood?

Scientists investigate the relationship between birth mass and the number of nephrons in the kidney.

The scatter diagram shows their results.

Describe the relationship shown by the scatter diagram.

Babies born with low birth mass are more likely to develop high blood pressure when they become adults.

Explain why protein in the urine of these adults may be an indication of kidney damage caused by high blood pressure.

Describe a simple test to show that a urine sample contains protein.

The diagram shows some structures in the human abdomen.

Which structure is used to store urine?

Which structure produces adrenaline?

Identify two substances that would be carried in structure R.

Tube T is used for excretion and reproduction in males, but only for excretion in females.

Explain this difference in function.

The volume and concentration of urine produced varies depending on the water content of the body.

Explain how very warm weather results in a change in the concentration and volume of the urine.