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| 3 | return blood to the heart (5) | 
 
 
| 5 | smallest branching blood vessel forming a network (9) | 
 
 
| 6 | type of blood the pulmonary veins are carrying (10) | 
 
 
| 9 | what is the name of the valve that prevent backflow of blood into the right atrium when the right ventricle contracts? (9) | 
 
 
| 10 | the heart is located within the _________ (11) | 
 
 
| 11 | these superior and inferior vessels enter the right atrium (5,5) | 
 
 
| 13 | the heart is composed of this type of muscle (7) | 
 
 
| 14 | these arteries carry deoxygenated blood to the lungs (9) | 
 
 
| 18 | the pulmonic and aortic valves are also known as _________ valves (9) | 
 
 
| 19 | how many chambers does the heart have? (4) | 
 
 
| 20 | what do the ventricles do while the atria contract? (5) | 
 
 
| 21 | region of heart where great vessels enter and leave (4) | 
 
 
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