Beginning with the return of blood from the body to the heart, trace the flow of blood through the ...

Answer to q. 1

Pathway as follows: inferior or superior vena cavae, right atrium, right atrioventricular valve, right ventricle, pulmonary semilunar valve, pulmonary arteries to lungs, pulmonary veins from lungs, left atrium, left atrioventricular valve, left ventricle, aortic semilunar valve, aorta.

Answer to q. 2

At higher altitudes there is less available oxygen. However, the main sensors controlling the rate of breathing respond to a rise in CO2 in the blood, not a lowered level of O2 . Therefore, a person can suffer from low enough levels of oxygen to experience symptoms of altitude sickness without triggering an increase in the rate of breathing.

Thank you

Can you answer the others that I've posted too?

I'll take a quick look at them