Interacting body system

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Across
  1. 2. what body system does the skin belong to?
  2. 3. what body system does the brain belong to?
  3. 5. what body system does the heart belong to?
  4. 6. what body system protects organs?
Down
  1. 1. what body system does the stomach belong to?
  2. 4. what body system do the kidneys belong to?