Gas Exchange in Humans

Question 1

what is the process of inspiration?

Answer 1

• internal intercostal muscles relax
• external intercostal muscles contract
• ribs are pulled upwards and outwards, increasing the volume of the thorax
• the diaphragm muscles contract and flatten, this increases the volume in the thorax
• the increase in the volume in the thorax results in the reduction of pressure in the lungs
• atmospheric pressure is greater than the pulmonary pressure so air is forced into the lungs

Question 2

what is expiration?

Answer 2

• internal intercostal muscles contract
• external intercostal muscle relax
• the ribs move downwards and inwards, decreasing the volume of the thorax
• diaphragm muscles relax and is pushed to the contents of the abdomen, decreasing the volume of the thorax
• decrease in volume in the thorax = increase of pressure in the lungs
• pulmonary pressure is greater than atmospheric pressure, so air is forced out of the lungs

Question 3

what is the difference between expiration and inspiration?

Answer 3

• inspiration is an active process so uses energy and expiration is a passive process