During inspiration, contraction of the diaphragm causes intrapleural pressure to become_____________?
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Answer: A. More negative
Explanation
During inspiration, contraction and flattening of the diaphragm expand the thoracic cavity volume. This expansion pulls the visceral pleura outward and causes intrapleural pressure to become more negative. Respiratory mechanics confirm that negative pleural pressure generates the pressure gradient needed for airflow. Intrapleural pressure represents the fluid pressure within the narrow potential space between lung pleurae. The chest wall naturally tends to expand outward while the elastic lungs recoil inward, creating baseline negativity. Inspiration enhances this negative pressure to draw atmospheric air into the expanding pulmonary alveoli.
Understanding pleural pressure mechanics is essential for managing patients requiring mechanical ventilation support. Pathological conditions like pneumothorax disrupt intrapleural negative pressure and cause lung collapse. Pulmonary function tests evaluate respiratory muscle strength and chest wall compliance dynamics. Intrapleural pressure becomes more negative rather than less negative during active inspiratory muscle contraction. Intrapleural pressure remains subatmospheric and negative throughout normal quiet breathing cycles. Intrapleural pressure is distinctly lower than intra-alveolar pressure to maintain lung expansion against recoil.
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