Reptilia, Aves and Mammalia · Zoology

Which structure separates the thoracic and abdominal cavities in mammals?

  1. The rib cage encasing the thoracic organs
  2. The sternum (breastbone) forming the ventral chest wall
  3. The diaphragm, a dome-shaped muscular sheet
  4. The pleura lining each lung
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Correct answer: The diaphragm, a dome-shaped muscular sheet

The diaphragm is a dome-shaped muscular partition unique to mammals. Its rhythmic contractions drive breathing by changing thoracic volume, and it forms the definitive anatomical boundary between the thoracic and abdominal cavities.

Difficulty: Medium Question 12 of 20

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