Sierras crossword puzzle

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Across
  1. 6. 4x 10x 40x
  2. 7. a hard mass
  3. 8. a group of tissues and organs that work together
  4. 9. Oxygen
  5. 10. heart
Down
  1. 1. mouth
  2. 2. water
  3. 3. the study of living organisms
  4. 4. muscles
  5. 5. brain and spinal cord