Revision Exercise (Breathing System & Transport System in Human)1. The photographs below show the sections of the lung tissues of a cigarette smoker and a non-smoker observed under the microscope with the same magnification:

(i) What is structure A? (1 mark)Air sac1

(ii) Describe and explain the mechanism by which air from the atmosphere is drawn into structure A.(4 marks)Intercostal muscle contracts and the ribs move upwards and outwards.Diaphragm muscle contracts to make the diaphragm flattened.These two actions increase the volume of the thoracic cavity.Thus the pressure inside the lung is lower than that of the atmosphere. Then the air moves into the structure A.1111

(iii) With reference to the photographs, explain how the function of structure A is affected by cigarette smoking (2 marks)The number and surface area of structure A (air sac) is reduced./ surface is less folded.This can greatly reduce the rate of gas exchange.11

(iv) (1)State a disease which may be caused by tar in cigarette smoke. (1 mark)lung cancer 1

(2)Draw a labeled diagram of a set-up used to show the presence of tar in cigarette smoke. (3 marks)Large and accurate diagram (D)Label and title (L) : *cigaittte, filter *pump, *cotton wool(No mark if the set-up is not workable)

A set-up to show the presence of tar in cigarette smoke

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[HKCEE 1997 #2a]

2. To study the effect of concentration of oxygen and carbon dioxide on the breathing rate, a healthy person was asked to inhale different gas mixtures. The results are shown in the table below:Gas mixtureConcentration of gas (%)Breathing rate(breaths per minute)

OxygenCarbon dioxide

P210.0317

Q214.0034

R160.0317

S164.0034

(i) With reference to the above information, state the factor that affects the breathing rate of the person. Explain how you arrive at your answer. (3 marks)Concentration of carbon dioxideAt a fixed O2 concentration, when the carbon dioxide concentration increases, the breathing rate will also increase.At a fixed CO2 concentration, when the oxygen concentration decreases, the breathing rate will not change.11

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(ii) Which of the four gas mixtures has similar concentrations of oxygen and carbon dioxide as exhaled air?(1 mark)S1

(iii) Mouth-to-mouth ventilation is a method for rescuing a person who fails to breathe but still has heartbeat. It involves blowing exhaled air into the patient's body through the mouth as shown below:

Based on the composition of exhaled air, explain why this method can help the patient stay alive before he can breathe again. (2 marks)Exhaled air still contains 16% oxygen.When blown into the patients lungs, the oxygen can be supplied to the body cell for respiration.11

(iv) Suggest why it is necessary to do the following when carrying out mouth-to-mouth ventilation:(1) Tilt the patient's head as shown in the diagram, instead of letting it lie flat. (1 mark)To ensure the entrance of the trachea is clear/ free from obstructions.1

(2) Observe whether the patient's chest rises when blowing air into the patient. (1 mark)To ensure that air is blown into the lungs. 1

[HKCEE 2003 #1a]3. The diagram below shows an air sac of the lung and its blood supply:

(i) Explain the importance of the water film in gaseous exchange. (2 marks)Oxygen in air dissolves in the water filmso that it can diffuse readily through the wall of air sac into the blood capillary.11

(ii) SARS patients may have fluid accumulated in the air sac. Explain how the accumulation of fluid may affect the oxygen content of the blood of the patients. (3 marks)The accumulation of fluid increases the distance for diffusion and reduces the surface area for dissolving oxygen,thereby decrease the rate of diffusion of dissolved oxygen into the blood capillaries.Thus the oxygen content of the blood decreases/ becomes lower than normal.1

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[HKCEE 2004 #1c]

4. The diagram below shows an air sac and its associated blood capillary of a heavy smoker:

(i) According to the diagram, state two adaptations of the air sacs for gas exchange. (2 marks)Air sacs have a large surface area to volume ratio. / The thin epithelium provides a short distance for rapid diffusion of gases. / Blood capillaries are in close contact with the air sacs.

Any two2 x 1

(ii) Name the gas that moves from the air in the air sacs to the blood. Explain how this happens.(4 marks)Oxygen.The oxygen concentration is higher in the air sacs than in the blood capillaries. Oxygen then dissolves in the film of moisture lining the air sacsand diffuses from the air sacs into the blood capillaries.1111

(iii) Substance X deposited on the inner surface of the air sac comes from cigarette smoke. (1 mark)What is substance X?Tar1

5. The graph below shows the pressure changes that occur in the two ventricles X and Y, during 2 consecutive cardiac cycles of a man at rest:

(i) With reference to the graph, calculate the number of heartbeats per minute of this man at rest. (1 mark)1

(ii) (1)Which of the ventricles, X or Y, is responsible for supplying blood to all parts of the body except the lungs ? (1 mark)X1

(2)Explain your answer with reference to the graph. (1 mark)X can produce greater pressure/ force to pump the blood to all parts of the body1

(iii) (1)State the function of the heart valves. (2 marks)To prevent the backflow of blood into the auricles / atriawhen the ventricles are contracting.OR To prevent the backflow of blood into the ventricles when the ventricles are relaxing.11

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(2)(I)What is the condition of the valves between the auricles and the ventricles at time A ? (1 mark)Closed.1

(II)Explain your answer with reference to the graph. (2 marks)At time A, the ventricular pressure is increasing,thus forcing the valves to close.11

(iv) Name the blood vessels which receive blood from the left and right ventricles respectively. Compare the oxygen content in their blood. (3 marks)From left ventricle: * aortaFrom right ventricle: * pulmonary arteryBlood in aorta contains more oxygen than that in the pulmonary artery.111

[HKCEE 1991 #4b]

6. The diagram below shows part of the circulatory system and its neighbouring cells:

(i) P is in the form of a highly branched network. Explain the importance of this feature to the function of P. (4 marks)The capillary network has a large total cross-sectional areaso reduces the rate of blood flow/ more time is allowed for the exchange of substances.

The numerous branches provide a large surface area for rapid exchange of substances between the blood and the tissue cells.11

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(ii) Describe how fluid B is formed from fluid A. (3 marks)The pressure of fluid A near the arterial end is higher than that of fluid BSome of the plasma except large proteins/ some of the blood except large proteins, red blood cells and plateletsare forced through the thin wall of the blood capillary/ P to form fluid B11

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(iii) (1)Substances in fluid C will eventually reach the heart. Which chamber of the heart first receives these substances ? (1 mark)Right atrium1

(2)Describe how the continuous flow to fluid C towards the heart is maintained. (2 marks)The contraction of skeletal muscles help to push fluid C along the lymph vessels,OR during inspiration, the drop in the pressure of the thoracic cavity helps to draw fluid C towards the heartThe valves of the lymph vessels prevent the backflow of lymph. 111

[HKCEE 1998 #3a]

7. The diagram below shows part of the human circulatory system:

(i) Describe how a continuous flow of lymph in vessel Y of the leg is maintained. (2 marks)Contraction of skeletal muscles around vessel Y forces the lymph to flow upward. The valves in vessel Y help to prevent the backflow of lymph11

(ii) For a patient suffering from a disease called elephantiasis, the lymph vessels in his leg are blocked by a kind of parasitic worm. The leg becomes greatly swollen due to the accumulation of tissue fluid. Explain why the tissue fluid accumulates. (2 marks)As the lymph vessels are blocked, tissue fluid in leg cannot be transported away.Meanwhile, it is continuously formed in the legthus tissue fluid accumulates.11

[HKCEE 2001 #3b]

8. The graph below shows the blood pressure of blood vessels at different locations of the pulmonary circulation:

(i) (1)Using the letters A to E in the graph, construct a flowchart to show the direction of blood flow from the heart along the pulmonary circulation. (1 mark)(Heart) B D E C A1

(2)State the criterion you should use in constructing the flowchart in (1). (1 mark)Blood flows from a high pressure region to a low pressure region.1

(ii) The blood vessels of two of the above locations show rhythmic changes in blood pressure. Explain how these blood pressure changes are related to the heart activity. (2 marks)When the ventricle of the heart contracts, blood is forced into the artery B, resulting in the increase of blood pressureBlood in the artery flows forward along the blood vessels while the ventricle of the heart relaxes, as a result the blood pressure drops./ When the ventricle of the heart relaxes, blood is forced out of the artery B, resulting in the decrease of blood pressure1

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(iii) State two blood components responsible for killing specific pathogens in the human body. (2 marks)White blood cells (lymphocyte/ phagocyte)Antibodies (Accept other alternatives)11

(iv) Immunity can be acquired by vaccination. Vaccine may be injected into the tissue under the skin. Describe how the vaccine can be transported to the heart after injection. (3 marks)Vaccine injected reaches the tissue fluidwhich drains back to lymph vessels/ capillaryand returns to the heart via a vein.111

[HKCEE 2008 #9b]

(v) If E is the capillary in the leg, and it is provided that it has low velocity of blood. Explain the importance of the low velocity of blood flow in the capillary. (2 marks)To allow more time for the exchange of materials between the blood and the tissue cells.11

(vi) In the vein of the leg, the blood pressure is very low while the velocity of blood flow is quite high. Describe how such a high velocity of blood flow in the vein is maintained. (2 marks)The volume of blood flow through each section of the circulation per unit time is the same.From the capillary to the vein, the total cross-sectional area decreases, so the velocity of blood flow increases. OR Contraction of skeletal muscle adjacent to the vein helps to force the blood to flow / inspiration helps to draw blood toward the thorax. At the same time, valves are present in the veins to prevent the backflow of the blood.11

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[HKCEE 2002 #4b]

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