A Levels Biology (9700)•9700/12/M/J/19
Explanation
Elastic Layer Functions in Arteries
Steps:
- Identify the elastic layer's role: stretches during systole to store energy and recoils in diastole to maintain pressure.
- Evaluate statement 1: Correct, as it buffers pressure changes by expanding and contracting.
- Evaluate statement 2: Incorrect, as the layer consists of elastin fibers, not smooth muscle (which is separate in tunica media).
- Evaluate statement 3: Correct, as recoil propels blood forward continuously.
Why B is correct:
- B selects 1 and 3, matching the accurate functions tied to arterial elasticity in cardiovascular physiology.
Why the others are wrong:
- A includes 2, which misattributes composition to muscle instead of elastin.
- C omits 3, ignoring the recoil mechanism for blood propulsion.
- D omits 1, neglecting pressure maintenance during heart relaxation.
Final answer: B
Topic: The circulatory system
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