1. They need oxygen to survive. This is because oxygen allows them to extract energy form food for us to use.

2. It gets to the cells from the lungs. For the oxygen to get to the lungs, people need to inhale it and it needs go down the trachea. Then, the lungs transfer the oxygen to the red blood cells in the blood stream. The cell picks up the oxygen from the red blood cells and delivers it to the hand.

3. The lung tissues, epithelial tissue, and red blood tissues. The lung tissue helps by breathing in the oxygen. The epithelial tissue helps because it protects the other important organs that deliver the oxygen. The red blood tissue helps by carrying the oxygen in the blood to the cell.

4. The lungs and the trachea, the heart, skin and the blood vessels. They help because they deliver he inhaled oxygen to the blood stream. The heart helps because it pumps the blood that delivers the oxygen. The blood stream because it carries the oxygen to the cells. The skin protects the organs while sending the oxygen to the needed cells.

5. The Respiratory System and Circulatory Systems. The respiratory system helps by inhaling the oxygen and then passing it on to the bloodstream and circulatory system. The circulatory system helps pump the blood, which contains the oxygen the cells need, throughout the body.