The kidney & the urinary system

During pregnancy the mother’s body undergoes several physiological changes to support the developing fetus. These changes affect every organ system in the body.

Changes to the heart and circulatory system begin in the first few weeks of pregnancy.

Fig. 16.1 shows the changes in stroke volume and heart rate that occur during pregnancy.

Fig. 16.1

Use the data in Fig. 16.1 to calculate the cardiac output in week 20.

Suggest an advantage of the increase in cardiac output.

Fig. 16.2 shows how blood pressure varies throughout pregnancy.

Fig. 16.2

A student looked at the data in Fig. 16.1 and Fig. 16.2 and drew the following conclusion:

‘As cardiac output increased blood pressure dropped so there must have been a decrease in vascular resistance.’

Evaluate this conclusion.

* Describe the flow of blood through the left side of the heart during the cardiac cycle and explain the role of valves and pressure differences in this process.

Additional answer space if required.

Another change that occurs in pregnancy is an increase in oxygen uptake by the mother. This is partly due to an increase in the mother’s metabolic rate and partly to supply the developing fetus.

Fig. 16.3 shows the oxygen dissociation curve for the mother’s haemoglobin.

Fig. 16.3

Sketch the oxygen dissociation curve for fetal haemoglobin.

Answer on Fig. 16.3.

Explain how the different affinities of maternal and fetal haemoglobin enable transfer of oxygen from the maternal circulation to the fetus.

Changes to kidney function during pregnancy can be confused with some diseases, such as chronic kidney disease or kidney failure.

The estimated glomerular filtration rate (eGFR) in a healthy 30–39-year-old is 107 cm³ min The eGFR usually decreases with age but in pregnancy, can increase by between 50 and 85%.

The table shows the results of some of the physiological measurements that a clinic carried out on two 35-year-old women. One of the patients was pregnant.

A doctor concluded that patient A was undergoing a normal pregnancy whereas patient B was suffering from kidney failure.

Explain the doctor’s conclusion.

Which statements about excretion and homeostasis are true, and which are false?

Tick (✓) one box in each row.

Fig. 19.1 is a drawing of a longitudinal section of a kidney.

Fig. 19.1

Identify the parts of the kidney labelled T, U and V.

Fig. 19.2 is a photomicrograph of a cross-section of part of the kidney.

Fig. 19.2

Using the letter T, U or V from Fig. 19.1, identify the part of the kidney that was used to make the cross-section in Fig. 19.2.

Give a reason for your identification.

Letter representing part of the kidney........

Fig. 19.3 is a diagram of a single nephron.

Fig. 19.3

Complete the table using the most appropriate letter or letters, W to Z, to show which part(s) of the nephron correspond to each of the statements.

Each letter may be used once, more than once or not at all.

Fig. 19.3 shows an increasing solute concentration.

Outline the processes in the loop of Henle that cause the solute concentration to increase.

An adult was advised to change their diet to reduce their body mass before undergoing surgery.

Over a period of several weeks their body mass reduced by 1 kg.

Suggest what happened to the 1 kg of body mass.

A student dissected a kidney. Fig. 1.1 shows one half of the dissected kidney.

Draw a simple diagram of the kidney in Fig. 1.1 in the space below.

On your diagram, label the pelvis, medulla and cortex.

A photomicrograph of a stained section of kidney tissue is shown in Fig. 1.2.

State one function of the distal convoluted tubule.

Describe the function of the structures labelled A in Fig. 1.2.

Suggest which lumen, B or C, has the highest concentration of urea. Explain your answer.

* Water reabsorption in the kidney is controlled by the endocrine and nervous systems.

Aldosterone and ADH are hormones that act on the kidney.

Aldosterone causes sodium ions to be pumped from the collecting duct cells into tissue fluid.

Describe how the endocrine and nervous systems work together to increase water reabsorption from the collecting duct.

Additional answer space if required.

Diuretics are drugs that decrease the reabsorption of water into the blood from the kidney.

Diuretics can change the concentration of ions and other molecules in the blood.

Some diuretics are used to treat high blood pressure.

The table below lists three different diuretics, X, Y and Z, and some of their effects in the

Suggest which of the diuretics, X, Y or Z, would be the most effective at reducing a person’s blood pressure. Explain your choice.

Suggest which of the diuretics, X, Y or Z, would be the most appropriate for use by a person with type II diabetes. Explain your choice.

The process of ultrafiltration in the kidney shares similarities with the formation of tissue fluid.

* Describe the similarities and differences between ultrafiltration and the formation of tissue fluid.

A person’s glomerular filtration rate (GFR) provides an indication of the health of their kidneys. The GFR is a measure of the volume of blood that can be filtered by the kidneys every minute.

GFR can be estimated by monitoring the blood concentration of creatinine, which is a breakdown product of creatine phosphate in muscles.

Suggest two characteristics of a patient that must be taken into account when using this GFR measurement to diagnose kidney damage.

Explain why each characteristic must be considered.

If kidney damage is suspected, the patient’s urine is likely to be tested for the protein albumin.

Explain why the presence of albumin in the urine indicates kidney damage.