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Biology
Blood and Circulation
| Question | Answer |
|---|---|
| what is an open circulatory system | the heart pumps blood into vessels that are open ended |
| do veins heave thin walls | yes |
| what are arterioles | they are smaller arteries |
| what is the heart wall made out of | involuntary muscle |
| what is the protective lkayer arounf the heart called | pericardium |