Questions: Inhale - Exhale

Inspiration is the process in which the intercostals muscles receive multiple nerve pulses, which cause them to contract. When the muscles contract the diaphragm does too. When the volume in the thoracic cavity increases, the elastic lungs stretch out because they are connected to the walls of the cavity, by a membrane called pleura. The lungs expand and the thorax expands. The lungs increase in volume and the expansion lowers the air pressure. The air molecules move from high to low pressure.

Expiration is when intercostals muscles and the diaphragm relax. The lungs are able to return to its original dome shape. During the process of relaxation, the volume of the thoracic cavity deceases. This causes the lungs to compress so they return to their original size. The air within the lungs is compressed and the exhaled air then flows out.

Inflation of the lungs are caused by the contractions of the thoracic cavity which increase the size of the lungs. The lungs expand and increase the volume of space within them.

Deflation of the lungs are caused by the relaxation of the intercostals muscles and diaphragm. When the volume of the thoracic cavity decreases the lungs compress/deflate.

Part of the process requires a muscle contraction of the diaphragm is inhalation.