Friday, September 6 (2019); Respiratory system
The normal mechanics of breathing can be described in terms of diaphragm, chest wall, pleural pressures and airflow. During inspiration, as the thoracic volume expands under the influence of respiratory muscle activity, the pleural pressure becomes more negative and generates a pressure gradient between the airway and the alveoli, which promotes inspiratory airflow. At the end of inspiration alveolar pressure equalises with atmospheric pressure, and there is no flow. During expiration, with relaxation of respiratory muscle, the thoracic volume decreases and the alveolar pressure exceeds atmospheric pressure, promoting expiratory air flow.