Musculoskeletal anatomy · USMLE Step 1

During a lung biopsy, a needle passes through the intercostal muscles. Which muscle layer is penetrated first?

  1. Innermost intercostal muscles
  2. Internal intercostal muscles
  3. External intercostal muscles
  4. Transversus thoracis
Show answer and explanation

Correct answer: External intercostal muscles

The external intercostal muscles form the superficial layer of the intercostal space. They assist with inspiration.

Difficulty: Medium Question 13 of 20

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