Explain with reasons.
Upward and downward movement of diaphragm occurs consecutively.
Diaphragm is a muscular partition which is present between the thoracic cavity and abdominal cavity. During the process of breathing, the upward and downward movement of diaphragm occurs simultaneuosly. When we inhale, the ribs rise up while the diaphragm lowers down simulatenously causing a decrease in pressure on lungs. This results in the moving of air into lungs through nose. As the ribs return to their original position, diaphragm rises up leading to the increase in pressure inside the lungs. This results in moving of the air outside the nose.