Korean Grade 8 Science 2 · MiraeN textbook · Chapter VI, Animals and Energy · Section 1, Digestion and Circulation · Subsection 3, Structure and Function of the Circulatory System (순환계의 구조와 기능), textbook pages 212–217.
Advanced practice examination. This is a separate, more challenging paper; the original fundamental test has not been changed. Questions are in English. No diagrams or external medical facts are required.
Suggested time: 80 minutes. Total: 50 questions, 100 marks. Work without consulting the answer key.
Scoring: Part A: 30 × 1 = 30 marks; Part B: 8 × 2 = 16 marks; Part C: 6 × 4 = 24 marks; Part D: 6 × 5 = 30 marks. Total = 100. In Part B, select exactly TWO answers; award both marks only when both choices are correct. In Parts C and D, award partial credit for scientifically correct work.
Part A — One Best Answer (30 questions, 30 marks)
Select the ONE most accurate answer (A–E) for each question.
1] A diagram shows a blood vessel carrying blood with very little oxygen. Which additional observation would prove that it is an artery rather than a vein?
A) Blood travels away from the heart.
B) Blood travels through the lungs.
C) The vessel carries carbon dioxide.
D) Blood contains red blood cells.
E) The vessel connects to capillaries.
2] A blood vessel leaves the right ventricle and reaches the lung capillaries. Which vessel is it?
A) A vein returning from body tissues
B) Pulmonary vein
C) Vena cava
D) Pulmonary artery
E) Aorta
3] Blood has just collected oxygen in the lungs and is travelling toward a heart chamber. Which vessel and chamber will it reach?
A) Pulmonary artery, then left atrium
B) Aorta, then left ventricle
C) Pulmonary vein, then right atrium
D) Vena cava, then right atrium
E) Pulmonary vein, then left atrium
4] A vessel is connected directly to the right atrium. Which description best fits the blood it normally carries?
A) Blood passing directly from the aorta into the right atrium
B) Blood returning from body tissues through a vein
C) Blood leaving the heart for lung capillaries
D) Blood leaving the left ventricle for the body
E) Blood arriving from the lungs through the pulmonary vein
5] If the connection between the right atrium and right ventricle were blocked, which next step in the normal circulation route would be directly prevented?
A) Blood leaving the left ventricle for the aorta
B) Blood exchanging substances in body capillaries
C) Blood entering the right ventricle from the right atrium
D) Blood moving from the lungs into the left atrium
E) Blood returning to the heart from the lungs
6] Which event normally happens immediately after blood enters the left atrium from the pulmonary vein?
A) It passes directly into body capillaries.
B) It crosses into the right atrium.
C) It passes into the left ventricle.
D) It returns to the pulmonary artery.
E) It enters the aorta directly.
7] The wall of the left ventricle is especially muscular. Which need best explains this feature?
A) It must stop blood clotting in the aorta.
B) It must pump blood through the whole body against substantial resistance.
C) It must exchange oxygen with cells through its wall.
D) It must make the greatest number of red blood cells.
E) It must receive blood from the vena cava at low pressure.
8] Imagine the valve between the right ventricle and pulmonary artery fails to prevent backflow. Which abnormal movement would it most directly permit?
A) Blood moving from the left ventricle into the aorta
B) Blood moving from the right atrium into the right ventricle
C) Blood moving from the pulmonary vein into the left atrium
D) Blood returning from the vena cava into body capillaries
E) Blood returning from the pulmonary artery into the right ventricle
9] Blood enters a capillary network among active body cells. Which combination of exchanges is most likely?
A) Oxygen and wastes enter blood; nutrients and carbon dioxide leave blood.
B) Oxygen and nutrients leave blood; carbon dioxide and wastes enter blood.
C) Oxygen leaves blood; nutrients and carbon dioxide both enter blood.
D) Oxygen and carbon dioxide both enter blood; nutrients leave blood.
E) Nutrients enter blood; oxygen and carbon dioxide both leave blood.
10] What is the major gas exchange as blood passes through lung capillaries?
A) Both gases leave blood.
B) Oxygen leaves blood and carbon dioxide enters it.
C) Neither gas crosses the capillary walls.
D) Carbon dioxide leaves blood and oxygen enters it.
E) Both gases enter blood.
11] A vessel carries blood immediately after it has been pumped out of a ventricle. Its wall is thick and elastic. Which explanation links the observation to function?
A) It must prevent blood returning from tissue capillaries by using many valves.
B) It must store dissolved nutrients as plasma.
C) It must provide the thinnest possible surface for gas exchange.
D) It must withstand the relatively high pressure produced by ventricular contraction.
E) It must allow blood cells to move into the ventricle through its wall.
12] Which observation would be most useful for distinguishing a vein from an artery in the textbook’s comparison?
A) A very thin wall designed mainly for exchange with cells
B) A thicker, more elastic wall built for ventricular pressure
C) A thinner, less elastic wall and valves that help prevent reverse flow
D) The presence of plasma, red cells and white cells
E) The presence of oxygen and carbon dioxide in the blood
13] Why can capillaries perform a function that the largest arteries and veins cannot perform as efficiently?
A) They contain plasma but no red blood cells.
B) They carry blood at the highest pressure in the body.
C) Their valves open when oxygen is needed.
D) Their very thin walls allow exchange with surrounding cells.
E) Their walls contract more forcefully than ventricles.
14] A labelled drawing shows blood moving through a tissue in the order X → Y → Z. X has a thick wall, Y is extremely thin, and Z has valves. What are X, Y and Z?
A) Vein, capillary, artery
B) Vein, artery, capillary
C) Artery, capillary, vein
D) Capillary, artery, vein
E) Artery, vein, capillary
15] A change makes a tissue capillary wall much thicker without changing the blood flow direction. Which function would be affected most directly?
A) The number of chambers inside the heart
B) Exchange of substances between blood and tissue cells
C) Blood leaving the left ventricle through the aorta
D) The existence of plasma in blood
E) The direction in which arteries carry blood
16] A microscope shows many biconcave disc-shaped cells without nuclei. Which function is most strongly associated with these cells?
A) Transporting oxygen with haemoglobin
B) Carrying dissolved nutrients as the liquid portion of blood
C) Helping a wound clot by forming platelets
D) Protecting the body by removing invading bacteria
E) Keeping blood from flowing backward through veins
17] A blood cell is larger than the other blood cells, has a nucleus, and can have an irregular outline. Which role matches it?
A) Preventing blood from flowing backward through heart valves
B) Pumping blood through the arteries
C) Forming the liquid part of blood
D) Helping protect the body against invading bacteria
E) Transporting most oxygen using haemoglobin
18] A blood sample contains small, irregular, nucleus-free cell fragments. Their main function is most likely to:
A) Exchange carbon dioxide directly with the lung air
B) Receive blood from the vena cava
C) Move dissolved nutrients through the plasma
D) Carry most of the oxygen in the sample
E) Help stop bleeding by promoting blood clotting
19] Blood is separated into its liquid fraction and its cellular fraction. Which statement about the liquid fraction is correct?
A) It contains only haemoglobin and oxygen.
B) It is mostly water and transports dissolved nutrients, carbon dioxide and wastes.
C) It is made of red blood cells and platelets alone.
D) It is the substance that forms heart valves.
E) It consists mainly of white blood cells with nuclei.
20] A student has fewer functioning red blood cells than expected, but the heart and blood vessels work normally. Which task would be reduced most directly?
A) Preventing backward flow through veins
B) Removing invading bacteria using white blood cells
C) Pumping blood from ventricles into arteries
D) Delivering oxygen to tissue cells
E) Clotting blood at a small cut
21] Which outcome is the most direct prediction if platelets do not perform their normal function?
A) A cut may bleed for longer before clotting.
B) All red blood cells immediately lose haemoglobin.
C) Pulmonary veins change into pulmonary arteries.
D) The left ventricle stops contracting.
E) Blood cannot enter the right ventricle.
22] An experiment compares white blood cells that can function normally with white blood cells that cannot. Which difference would be most directly expected?
A) The number of atria and ventricles
B) The rate of oxygen exchange across heart valves
C) The direction of blood flow in the vena cava
D) The thickness of the aortic wall
E) The body’s ability to defend against bacteria
23] Which substance is transported mainly as dissolved material in plasma rather than as the principal cargo of haemoglobin in red blood cells?
A) Nutrients absorbed from the digestive system
B) The red pigment that colours erythrocytes
C) The muscular tissue of heart chambers
D) Valves between an atrium and a ventricle
E) Most of the oxygen carried to body cells
24] A blood drop has just left the left ventricle. Which named vessel does it enter next?
A) Pulmonary vein
B) Vena cava
C) A body vein returning to the right atrium
D) Pulmonary artery
E) Aorta
25] The blood in a body tissue vein is approaching the heart. Which named vessel and chamber complete this return in the simplified textbook route?
A) Vena cava → right atrium
B) Aorta → left ventricle
C) Pulmonary vein → left atrium
D) Aorta → right atrium
E) Pulmonary artery → right ventricle
26] Which pair correctly identifies the starting and ending chambers of pulmonary circulation?
A) Left ventricle → right atrium
B) Right ventricle → left atrium
C) Left atrium → right ventricle
D) Right atrium → left ventricle
E) Right ventricle → right atrium
27] Which pair correctly identifies the starting and ending chambers of systemic circulation?
A) Left atrium → right ventricle
B) Right atrium → left atrium
C) Left ventricle → left atrium
D) Right ventricle → left atrium
E) Left ventricle → right atrium
28] A student follows a single blood sample through both the lungs and the rest of the body. How often does it pass through the heart during one complete linked circuit?
A) Twice
B) Once
C) It does not pass through the heart
D) Three times
E) Four times
29] Two vessels are described. Vessel X carries oxygen-poor blood from the heart to the lungs. Vessel Y carries oxygen-rich blood from the lungs to the heart. Which identification is correct?
A) X = pulmonary vein; Y = pulmonary artery
B) X = aorta; Y = vena cava
C) X = pulmonary artery; Y = pulmonary vein
D) X = pulmonary artery; Y = vena cava
E) X = vena cava; Y = aorta
30] An artery serving a body tissue becomes narrower. Assuming the heart continues to pump, which consequence is the most reasonable based on the textbook’s description of circulation?
A) White blood cells will turn into red blood cells.
B) Blood in the vessel will immediately stop containing plasma.
C) Less blood may reach the downstream tissue, reducing delivery of oxygen and nutrients.
D) The artery will become a vein because blood pressure is lower.
E) The tissue will obtain oxygen directly from heart valves.
Part B — Select TWO Answers (8 questions, 16 marks)
Each question has exactly TWO correct choices. Select both. No partial credit is awarded for selecting only one correct choice.
31] Select the TWO statements that correctly link heart structures to their functions.
A) Atria pump directly into the aorta.
B) Ventricles pump blood into arteries.
C) Atria receive blood from veins.
D) Heart valves normally encourage blood to flow backward.
E) Ventricular walls are generally thinner than atrial walls.
32] Select the TWO statements about artery and vein structure that are correct.
A) Veins generally have thinner, less elastic walls and valves against reverse flow.
B) Capillaries have the thickest walls of the three main vessel types.
C) Arterial walls are thick and elastic enough to withstand relatively high pressure.
D) Arteries are identified by their high oxygen content in every case.
E) Veins always carry blood away from the heart.
33] Select the TWO statements that correctly describe pulmonary circulation.
A) It returns directly to the right atrium through the vena cava.
B) It starts when the left ventricle sends blood into the aorta.
C) It begins at the right ventricle.
D) It returns blood to the left atrium through the pulmonary vein.
E) Blood gains carbon dioxide from lung air and loses oxygen.
34] Select the TWO statements that are true about systemic circulation.
A) Blood leaves the right ventricle through the pulmonary artery.
B) In body capillaries, blood normally gains oxygen from cells.
C) It ends when blood enters the left atrium through the pulmonary vein.
D) Blood leaves the left ventricle through the aorta.
E) In body capillaries, blood supplies oxygen and nutrients to cells.
35] A microscope and a blood sample are examined. Select the TWO accurate observations.
A) Plasma is a type of red blood cell.
B) White blood cells generally have nuclei and may have irregular shapes.
C) White blood cells are the principal oxygen carriers because of haemoglobin.
D) Platelets are the largest blood cells and each has a prominent nucleus.
E) Mature red blood cells are numerous, nucleus-free, and depressed at the centre.
36] Select the TWO changes that most directly match a loss of a blood component’s normal function.
A) Reduced platelet activity can make it harder to stop bleeding.
B) Reduced platelet activity removes the nucleus from white blood cells.
C) Reduced plasma volume turns veins into capillaries.
D) Reduced red-blood-cell function can decrease oxygen delivery.
E) Reduced white-blood-cell function makes arteries carry blood toward the heart.
37] Select the TWO statements that correctly describe gas exchange and oxygen content.
A) Body capillaries normally transfer oxygen from cells into blood.
B) Pulmonary arteries can carry oxygen-poor blood while still being arteries.
C) All veins must carry oxygen-poor blood by definition.
D) Pulmonary veins carry blood away from the heart.
E) In lung capillaries, blood takes in oxygen and releases carbon dioxide.
38] A student traces blood continuously through both linked circulation routes. Select the TWO correct transitions.
A) Left atrium → left ventricle → aorta
B) Right atrium → left ventricle → pulmonary artery
C) Right atrium → right ventricle → pulmonary artery
D) Left atrium → right ventricle → vena cava
E) Right ventricle → aorta → body capillaries
Part C — Put the Steps in Order (6 questions, 24 marks)
Rearrange every item into one scientifically correct sequence. Write the full sequence using arrows. Each question is worth 4 marks.
39] Put these six structures in the order visited by blood, beginning in the right atrium and ending in the left atrium. Use each exactly once.
Scrambled items: Pulmonary vein · Right atrium · Lung capillaries · Left atrium · Pulmonary artery · Right ventricle
Your sequence: __________________________________________________________________
40] Put these five structures in the order visited during systemic circulation, beginning in the left ventricle.
Scrambled items: Vena cava · Body capillaries · Left ventricle · Right atrium · Aorta
Your sequence: __________________________________________________________________
41] Arrange these six structures to trace one blood sample from the lungs to the body tissues.
Scrambled items: Aorta · Left ventricle · Pulmonary vein · Body capillaries · Lung capillaries · Left atrium
Your sequence: __________________________________________________________________
42] Arrange these six structures to trace oxygen-poor blood leaving body tissues until it reaches the lungs.
Scrambled items: Right ventricle · Body capillaries · Lung capillaries · Vena cava · Pulmonary artery · Right atrium
Your sequence: __________________________________________________________________
43] Starting just after blood returns from the lungs, arrange these five events into a biologically correct sequence.
Scrambled items: Blood enters the aorta. · The left ventricle contracts. · Blood enters the left atrium. · Blood reaches body capillaries. · Blood passes into the left ventricle.
Your sequence: __________________________________________________________________
44] Beginning when blood leaves a ventricle, arrange the five types of structure in the order encountered before blood reaches an atrium again.
Scrambled items: Capillary · Atrium · Vein · Ventricle · Artery
Your sequence: __________________________________________________________________
Part D — Explain and Apply (6 questions, 30 marks)
Write a clear scientific explanation. Use the textbook’s terminology. Each response is worth 5 marks.
45] A student writes: ‘Every artery contains oxygen-rich blood, and every vein contains oxygen-poor blood.’ Explain why this is not a reliable definition. Name the two pulmonary vessels that demonstrate the problem.
Answer: __________________________________________________________________
__________________________________________________________________
__________________________________________________________________
46] Explain how the structures of arteries, veins and capillaries suit their different functions. Give one structure–function link for each vessel type.
Answer: __________________________________________________________________
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__________________________________________________________________
47] Three hypothetical patients have different blood-component problems: A has too few effective red blood cells; B has too few effective white blood cells; C has too few effective platelets. Predict the most directly affected function for A, B and C, and explain one prediction.
Answer: __________________________________________________________________
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48] Compare systemic circulation with pulmonary circulation. For each, name the starting and ending heart chambers and describe the main exchange occurring in its capillaries.
Answer: __________________________________________________________________
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49] In a hypothetical experiment, the walls of body capillaries become much thicker, but the heart still beats and blood still flows. Predict which process is impaired first. Explain why simply increasing the number of red blood cells would not fully solve the structural problem.
Answer: __________________________________________________________________
__________________________________________________________________
__________________________________________________________________
50] The textbook asks what may happen when an artery becomes progressively narrower. Predict two effects on the downstream tissues and explain how blood circulation normally prevents those problems. Do not diagnose a named disease.
Answer: __________________________________________________________________
__________________________________________________________________
__________________________________________________________________
Teacher Answer Key and Marking Guidance
The key begins here. For constructed responses, accept scientifically equivalent wording. The textbook is the primary reference for all answers.
Part A — One Best Answer
1] A. Blood travels away from the heart.
Arteries are defined by blood-flow direction, not by oxygen content. The pulmonary artery is a key exception to the usual oxygen-rich pattern.
2] D. Pulmonary artery
The right ventricle pumps blood into the pulmonary artery, which carries it to the lungs.
3] E. Pulmonary vein, then left atrium
The pulmonary vein returns oxygen-rich blood from the lungs to the left atrium.
4] B. Blood returning from body tissues through a vein
The vena cava brings returning systemic blood into the right atrium.
5] C. Blood entering the right ventricle from the right atrium
Normal flow through the right side is right atrium → right ventricle → pulmonary artery.
6] C. It passes into the left ventricle.
The left atrium receives blood; the left ventricle then pumps it into the aorta.
7] B. It must pump blood through the whole body against substantial resistance.
Ventricles have thicker muscular walls than atria because they drive blood into arteries. The left ventricle supplies systemic circulation.
8] E. Blood returning from the pulmonary artery into the right ventricle
The valve at a ventricle–artery junction prevents reverse movement from the artery into the ventricle.
9] B. Oxygen and nutrients leave blood; carbon dioxide and wastes enter blood.
Body cells receive oxygen and nutrients and release carbon dioxide and wastes into the blood.
10] D. Carbon dioxide leaves blood and oxygen enters it.
Pulmonary circulation transfers carbon dioxide out of blood and oxygen into blood.
11] D. It must withstand the relatively high pressure produced by ventricular contraction.
Thick, elastic arterial walls help withstand pressure from the ventricles.
12] C. A thinner, less elastic wall and valves that help prevent reverse flow
The textbook contrasts thin-walled, valved veins with thicker-walled arteries.
13] D. Their very thin walls allow exchange with surrounding cells.
The very thin capillary walls are adapted for exchange of substances.
14] C. Artery, capillary, vein
Blood passes through arteries, then capillary exchange networks, then veins.
15] B. Exchange of substances between blood and tissue cells
A thicker exchange barrier would make transfer between blood and nearby cells more difficult.
16] A. Transporting oxygen with haemoglobin
Mature red blood cells are abundant, lack nuclei, are disc-shaped with depressed centres, and transport oxygen.
17] D. Helping protect the body against invading bacteria
White blood cells are the largest blood cells described and have nuclei; they defend against invading bacteria.
18] E. Help stop bleeding by promoting blood clotting
Platelets are the smallest listed blood components and help blood coagulate at a wound.
19] B. It is mostly water and transports dissolved nutrients, carbon dioxide and wastes.
Plasma is the mostly watery, liquid component of blood, carrying several dissolved substances.
20] D. Delivering oxygen to tissue cells
Red blood cells are responsible for most oxygen transport.
21] A. A cut may bleed for longer before clotting.
Platelets are involved in coagulation, which helps stop bleeding.
22] E. The body’s ability to defend against bacteria
The protective role of white blood cells is to help remove invading bacteria.
23] A. Nutrients absorbed from the digestive system
Plasma carries dissolved nutrients; red blood cells carry oxygen using haemoglobin.
24] E. Aorta
The aorta carries blood from the left ventricle into systemic circulation.
25] A. Vena cava → right atrium
Systemic blood returns through the vena cava to the right atrium.
26] B. Right ventricle → left atrium
Pulmonary circulation is right ventricle → pulmonary artery → lung capillaries → pulmonary vein → left atrium.
27] E. Left ventricle → right atrium
Systemic circulation starts at the left ventricle and returns through the vena cava to the right atrium.
28] A. Twice
The textbook identifies pulmonary and systemic circulation as linked processes that take blood through the heart twice.
29] C. X = pulmonary artery; Y = pulmonary vein
Pulmonary artery blood leaves the heart; pulmonary vein blood returns from the lungs.
30] C. Less blood may reach the downstream tissue, reducing delivery of oxygen and nutrients.
Narrowing can restrict flow to a region, limiting delivery of materials needed by tissue cells. This is a qualitative inference, not a diagnosis.
Part B — Select TWO Answers
31] B and C. Atria receive blood from veins. / Ventricles pump blood into arteries.
Atria receive returning blood through veins; ventricles push blood out into arteries. Valves prevent reverse movement.
32] A and C. Arterial walls are thick and elastic enough to withstand relatively high pressure. / Veins generally have thinner, less elastic walls and valves against reverse flow.
Wall thickness, elasticity and venous valves relate to the pressure and direction of blood flow.
33] C and D. It begins at the right ventricle. / It returns blood to the left atrium through the pulmonary vein.
The pulmonary route runs from the right ventricle through lung capillaries and returns through pulmonary veins to the left atrium.
34] D and E. Blood leaves the left ventricle through the aorta. / In body capillaries, blood supplies oxygen and nutrients to cells.
The systemic route supplies body tissues and returns to the right atrium.
35] B and E. Mature red blood cells are numerous, nucleus-free, and depressed at the centre. / White blood cells generally have nuclei and may have irregular shapes.
These match the cell descriptions in the textbook; platelets are small and nucleus-free, and plasma is liquid.
36] A and D. Reduced platelet activity can make it harder to stop bleeding. / Reduced red-blood-cell function can decrease oxygen delivery.
Platelets enable clotting, and red blood cells carry oxygen. The other options invent changes unrelated to those components.
37] B and E. In lung capillaries, blood takes in oxygen and releases carbon dioxide. / Pulmonary arteries can carry oxygen-poor blood while still being arteries.
Gas exchange differs in lungs and tissues; arteries and veins are named for flow direction rather than oxygen content.
38] A and C. Right atrium → right ventricle → pulmonary artery / Left atrium → left ventricle → aorta
Right-sided pumping supplies the pulmonary artery, while left-sided pumping supplies the aorta.
Part C — Ordered Sequences
39] Right atrium → Right ventricle → Pulmonary artery → Lung capillaries → Pulmonary vein → Left atrium
The right side sends blood to the lungs, which return oxygenated blood to the left atrium.
40] Left ventricle → Aorta → Body capillaries → Vena cava → Right atrium
The left ventricle pumps blood into the aorta; systemic blood then travels via capillaries and veins back to the right atrium.
41] Lung capillaries → Pulmonary vein → Left atrium → Left ventricle → Aorta → Body capillaries
Oxygen-rich blood returns from the lungs through the pulmonary vein and left heart before systemic distribution.
42] Body capillaries → Vena cava → Right atrium → Right ventricle → Pulmonary artery → Lung capillaries
Blood from body tissues returns via the vena cava and is pumped from the right ventricle to lung capillaries.
43] Blood enters the left atrium. → Blood passes into the left ventricle. → The left ventricle contracts. → Blood enters the aorta. → Blood reaches body capillaries.
Atrial reception precedes ventricular filling, contraction and systemic delivery.
44] Ventricle → Artery → Capillary → Vein → Atrium
A ventricle pumps blood into an artery; capillary exchange occurs before venous return to an atrium.
Part D — Model Responses
45] Model answer: Arteries are defined by carrying blood away from the heart, and veins by carrying blood toward the heart. The pulmonary artery carries oxygen-poor blood from the right ventricle to the lungs. The pulmonary vein carries oxygen-rich blood from the lungs to the left atrium.
Suggested 5-mark rubric: 1 mark for artery direction; 1 for vein direction; 1 for pulmonary artery and its oxygen content; 1 for pulmonary vein and its oxygen content; 1 for complete coherent explanation.
46] Model answer: Arteries have thick, elastic walls to withstand relatively high pressure from ventricular pumping. Veins have thinner, less elastic walls and valves that help prevent backflow as blood returns to the heart. Capillaries have extremely thin walls to allow exchange with nearby tissue cells.
Suggested 5-mark rubric: 1 mark each for the three correct vessel structures; 1 mark for accurate pressure/backflow function; 1 mark for capillary exchange.
47] Model answer: A: oxygen transport to body cells is reduced. B: protection against invading bacteria is reduced. C: blood clotting and stopping bleeding are impaired. For example, A is affected because red blood cells contain haemoglobin and transport oxygen.
Suggested 5-mark rubric: 1 mark for each of A, B and C; 1 for correctly linking a component to its mechanism; 1 for a clear explanation.
48] Model answer: Systemic circulation begins at the left ventricle and ends at the right atrium; body cells receive oxygen and nutrients while blood collects carbon dioxide and wastes. Pulmonary circulation begins at the right ventricle and ends at the left atrium; blood releases carbon dioxide and receives oxygen in lung capillaries.
Suggested 5-mark rubric: 1 each for systemic and pulmonary starting chambers; 1 each for correct ending chambers; 1 for distinguishing exchange in the two capillary beds.
49] Model answer: Material exchange between blood and tissue cells becomes more difficult because substances must cross a thicker capillary wall. Even if blood has more red blood cells available to carry oxygen, the thicker barrier would still limit transfer of oxygen from blood to tissue cells.
Suggested 5-mark rubric: 1 for naming exchange; 2 for explaining the capillary-wall barrier; 1 for distinguishing oxygen transport from transfer; 1 for coherent prediction.
50] Model answer: Less blood may reach the downstream tissues, reducing oxygen delivery and nutrient supply; removal of carbon dioxide and wastes may also be impaired. Normal circulation continuously supplies oxygen and nutrients and removes waste products from tissues.
Suggested 5-mark rubric: 1 for reduced blood delivery; 1 each for two sensible tissue effects; 1 for normal supply; 1 for normal waste removal.
Source and scope: MiraeN Science 2, pp. 212–217. Applications such as narrowing an artery or thickening capillary walls are explicitly hypothetical reasoning exercises derived from the textbook’s structure–function explanations. No clinical diagnosis is required.
