Question

Describe the mechanism of breathing in man.? (for 5 marks)

Answer 1

The action of breathing in and out is due to changes of pressure within the thorax, in comparison with the outside. This action is also known as external respiration. When we inhale the intercostal muscles (between the ribs) and diaphragm contract to expand the chest cavity

Answer 2

We breathe in oxygen-rich or pure air from the atmosphere. It reaches the lungs and fills upp the air sacs. This causes the lungs and chest to expand. The sacs have very thin skin. There are many blood vessels in this thin skin. The exchange of gases take place here. The blood picks up the oxygen and gives out carbon dioxide into the air in the sacs. This air which is rich in carbon dioxide or impure air goes out through our nostrils when we exhale.