MCAT Biology Question 158: Answer and Explanation

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Question: 158

8. When the knee moves back and forth during walking, what prevents the surfaces of the leg bones from rubbing against each other?

  • A. Articular cartilage
  • B. Epiphyses
  • C. Synovial fluid
  • D. Smooth muscle

Correct Answer: A

Explanation:

The articular surfaces of the bones are covered with a layer of smooth articular cartilage. The epiphysis is a portion of the bone itself, eliminating choice (B). Synovial fluid lubricates the movement in the joint space, but does not stop the bones from contacting one another; this is the job of articular cartilage, eliminating choice (C). There is no appreciable function for smooth muscle in the joint space, eliminating choice (D).

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