People who climb Mount Everest—the tallest mountain in the world—often need to carry oxygen tanks. The oxygen tanks help them breathe at the highest elevations. What creates the need for extra oxygen? Can you write a more detailed explanation of why climbers need oxygen tanks as they near the top of Mount Everest?

Explanation:

When people get to higher attitude  the amount of gas molecules in the air

becomes limited, since that happens it means that people will need more oxygen to have the blood flowing to be steady, so that's why people will carry portable oxygen tanks.

Bonus- "This makes it harder to breathe because you need to inhale"

the major parts of the digestive system:

salivary glands.

pharynx.

esophagus.

stomach.

small intestine.

large intestine.

rectum.

accessory digestive organs: liver, gallbladder, pancreas.