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ICSE Question Bank
2018Q1(f)(v)The Circulatory System
Short answerModerate1 mark
1(f)

Choose between the two options to answer the question specified in the brackets for the following: Example: Corolla or Calyx (Which is the outer whorl?) Answer: Calyx

Blood in the pulmonary artery or pulmonary vein (Which one contains less oxyhaemoglobin?)

Topic: Oxyhaemoglobin in the pulmonary artery

Previous-year question practice database

Answer

Exam answer

The PULMONARY ARTERY.

Explanation

THE PULMONARY VESSELS ARE THE GREAT EXCEPTION to the usual rule, and this question tests exactly that: PULMONARY ARTERY — carries DEOXYGENATED blood FROM the heart TO the lungs. Less oxyhaemoglobin. PULMONARY VEIN — carries OXYGENATED blood FROM the lungs TO the heart. More oxyhaemoglobin.

Everywhere else in the body an artery carries oxygenated blood and a vein deoxygenated. Here it is reversed, because these vessels run to and from the LUNGS rather than the body.

THE RULE THAT NEVER FAILS: an artery is defined by DIRECTION — it carries blood AWAY from the heart, and a vein TOWARDS it. The oxygen content is merely usual, not definitional.

The umbilical vessels of a foetus are reversed in the same way.

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