The alveoli is where the oxygen moves out of the lungs and into the blood. At the same time carbon dioxide moves out of the blood and into the lungs to be exhaled.
Your brain and heart hope this helps
The normal force(the force pushing up from a flat surface) is equal to the force of gravity (the force pushing down on the object) at 5N so they cancel each other out. The other two forces are going in opposite directions, one positive and one negative. Subtracting 10N-5N would give you the amount of force that is not canceled (5N) in the direction of the biggest force (to the left)