The respiratory system

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Across
  1. 1. is a body fluid in humans and other animals that delivers necessary substances
  2. 3. blood vessels that carry blood towards the heart
  3. 4. an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs
  4. 6. largest artery in the body
Down
  1. 2. is one of four chambers of the heart
  2. 5. is the first chamber to receive deoxygenated blood returning from the body