This is SBP Paper 2 Trial SPM 2009...It is about placenta..and in real SPM Biology, there is one question about placenta in paper 2 too...
Diagram 5 shows prenatal development of a human embryo.
(a)(i)Name two materials that pass via R(placenta) from mother to the foetus.
(ii)Name two materials in blood of mother that are partially prevented by R (placenta) from entering the blood of foetus.
(b)Explain how the structure of R enable a rapid exchange of materials to take place [2m]
(c)State two differences between the content of R and foetal blood.[2m]
(d) R regress and cause miscarriage.
Explain the above statement.[2m]
(e) Explain why colostrums valuable to the baby immediately after birth.[2m]
Suggested Answer:
(a)(i) Able to name the materials that can pass via placenta
Sample answer:
water / amino acid / glucose /nutrients / oxygen /antibodies
(ii) Able to name the materials that partially prevented by placenta
Sample answer :
Drugs / alcohol / caffeine / nicotine / HIV / rubella virus
(b)Able to explain the adaptation of the structure R
Sample answer :
F1 : placenta has a large surface area to volume ratio.
P1 : to increase exchange rate
F2 : material and embryonic bloods are brought into close contact.
P2 : diffusion can take place efficiently
F3 : separated only by a thin membrane
P3 : diffusion can take place efficiently
Any F with correspond P
(c) R Foetal blood
Oxygen high low
nutrient high low
Carbon dioxide low high
Waste / example Low high
(d)Sample answer :
F : placenta acts as an endocrine gland // secreting oestrogen/progesterone.
P : (these hormone) help to maintain a thickened / blood enriched endometrium throughout the pregnancy.
(e) Able to explain the importance of colostrums to newborn baby.
Sample answer :
F : colostrums contain antibodies
P : to help infant / baby survive from pathogens .
...................................and the immunity foetus get from mother is passive natural!
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