SPM Biology 2018


7) Diagram 7.1 shows the parts of blood circulatory and lymphatic system in human.

Rajah 7.1 menunjukkan sebahagian system peredaran darah dan system limfa pada manusia.

(a) Explain how fluid Q is formed.

Terangkan bagaimana bendalir Q terbentuk.

(b) Describe the similarities and differences between fluids P and R.

Huraikan persamaan dan perbezaan antara bendalir P dan bendalir R.

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(c) Diagram 7.2 shows a type of worm which is transmitted by mosquitoes to human. The mosquito is the vector of disease X. Discuss how disease X occurs. Suggests ways to prevent the disease.

Rajah 7.2 menunjukkan sejenis cacing dipindahkan oleh nyamuk keapada manusia. Nyamuk tersebut adalah vector kepada penyakit X. Bincangkan bagaimana penyakit X terjadi. Cadangan Langkah-langkah untuk mengelakkan penyakit tersebut.

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Answer ( 1 )


    7. a) Fluid Q is interstitial fluid. The capillaries have a smaller diameter compared to the arterioles, this causes blood entering the arterial end of capillaries to be under high pressure. This high pressure causes fluid to be filtered out (diffuse out) from the blood plasma into the extracellular space (spaces between the cells). This fluid then becomes the interstitial fluid.


    b) Fluid P is blood while fluid R is lymph.

    Fluid P (blood)  Fluid R (lymph)
    Is red in colour due to the presence of red blood cells (haemoglobin). Is transparent and yellowish in colour.
    Found in blood vessels (circulatory system) Found in lymph vessels (lymphatic system)
    Blood contains plasma that when diffuses out of blood capillaries becomes interstitial fluid. Lymph consists of interstitial fluid that has not been reabsorbed into the blood capillaries. This interstitial fluid diffuses into the lymph capillaries to make up lymph.
    Blood consists of plasma and cellular components. Lymph consists of plasma and lymphocytes.
    Blood contains cellular components like erythrocytes, leukocytes and platelets . Lymph does not contain plasma proteins, erythrocytes and platelets. 

    Contains a large number of lymphocytes which are leukocytes.

    Blood is important for the transportation of respiratory gases (oxygen and carbon dioxide), nutrients, hormone and waste products. Forms part of the immune system helps with the defense mechanism against foreign substances like pathogens.


    c) Disease X is termed as lymphatic filariasis or elephantiasis. It is caused by parasitic roundworms. Worm larvae present in blood migrates from the blood vessels to the lymphatic vessels. When the worm larvae mature into adult worms they can lodge in the lymphatic vessels. This creates a blockage and lymph cannot be returned to the bloodstream. Thus, lymph starts to accumulate within the lymph vessels which creates this bulging (swollen) of the skin.

    Disease X is caused by mosquito vectors, thus to prevent this disease from occurring, we have to reduce the number of mosquitoes by using mosquito repellents or pesticides. Furthermore, during the night sleeping within a mosquito net can help prevent mosquitoes bites from occurring. Wearing long sleeves and long pants can also prevent mosquito bites as well. Another way is to use drugs to kill off the microfilariae, so that they don’t mature to produce more larvae.

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