8.1. The circulatory system
A subsection of Biology, 9700, through 8. Transport in mammals
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Using a light microscope at a magnification of ×400, it is possible to identify different types of blood cell in prepared slides of mammalian blood. is a key to identify different types of blood cell in prepared slides of mammalian blood. In , letters C, D, E and F represent four different types of blood cell. key 1a nucleus present go to 2 1b nucleus absent C 2a large rounded nucleus D 2b nucleus not rounded go to 3 3a nucleus is kidney shaped E 3b nucleus is lobed F Identify the cell types C, D, E and F in . C D E F Explain why blood taken from a person with an infectious disease may have a different number of white blood cells compared with blood taken from a healthy person. As part of a research project, a team of doctors and scientists carried out tests to investigate the effect of altitude on the ability of blood to carry oxygen. They assessed the changes in the oxygen-carrying ability of their own blood as they walked from 1530 m above sea level to 5700 m above sea level, over a period of 14 days. 5700 m above sea level is an extremely high altitude. Table 4.1 is a summary of some of their results. Table 4.1 day 1 at 1530 m day 14 at 5700 m percentage saturation of haemoglobin with oxygen in blood leaving the lungs volume of oxygen delivered to tissues by 100 cm3 of blood / cm3 19.3 19.2 Compare the results for day 1 with the results for day 14 in Table 4.1 and explain the results shown for day 14. The results of the research project have led to an improved understanding of diseases such as sickle cell anaemia. Explain why sickle cell anaemia is an example of a disease.
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THEORY
2021
Paper 2, Variant 2
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The red blood cells of people with sickle cell anaemia have reduced oxygen-carrying capacity. Explain the relationship between the gene mutation that causes sickle cell anaemia and the reduced oxygen-carrying capacity of red blood cells. People with sickle cell anaemia may need a blood transfusion. One risk associated with a blood transfusion is a condition known as transfusion-associated circulatory overload (TACO). TACO is caused by a large increase in blood volume over a short period of time. This increase in blood volume can be harmful. Predict the effect of an increase in blood volume on ADH secretion and state one consequence for kidney function of this change in ADH secretion. One feature of TACO is an increase in fluid entering the alveoli, which makes it difficult to breathe. This increase in fluid can be caused by an increase in blood pressure in the pulmonary capillaries that surround the alveoli. Suggest how an increase in blood pressure in the pulmonary capillaries can cause fluid to enter the alveoli. People with kidney disease may be at a higher risk of TACO following a blood transfusion. A study carried out in 2019 investigated whether there is a link between kidney disease and TACO. This study included data from: • 200 people who developed TACO after a blood transfusion • 405 people who did not develop TACO after a blood transfusion. The people in the study were put into one of four categories: • people with acute (short-term) kidney injury (AK• people with chronic (long-term) kidney disease (CKD) who do not require dialysis • people with severe chronic kidney disease who do require dialysis (CKD + D) • people who do not have kidney disease. In dialysis, a machine is used to carry out the function of the kidneys. The results of this study are shown in . AKI CKD category percentage of people CKD + D no kidney disease key percentage of the 200 people who developed TACO percentage of the 405 people who did not develop TACO With reference to , describe the effect of having kidney disease on the risk of developing TACO. Suggest reasons for this effect. Patients who are at high risk of developing TACO following a blood transfusion can be given a type of drug called a loop diuretic. In normal urine production, 99% of sodium ions in the glomerular filtrate are reabsorbed and 1% are excreted. In urine production of people who take loop diuretics, 80% of sodium ions in the glomerular filtrate are reabsorbed and 20% are excreted. Explain how loop diuretics affect water reabsorption in the kidneys and suggest why this reduces the risk of developing TACO following a blood transfusion.
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THEORY
2022
Paper 4, Variant 2
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Questions Discovered
175