Final answer:
Posterior chest expansion is assessed to understand the elasticity and functioning of the thoracic wall during breathing, which is important for diagnosing respiratory conditions.
Step-by-step explanation:
To examine posterior chest expansion, healthcare providers assess the ability of the thoracic wall to stretch during inspiration. During inhalation, the muscles of the thorax facilitate breathing by expanding the size of the thoracic cavity, allowing the lungs to fill with air due to the lower intrapleural pressure. When we exhale, the lungs recoil, and the chest wall along with the diaphragm returns to its original position. Thoracic wall compliance, which is the elasticity of the chest wall, directly affects how easily the chest can expand and, consequently, affects the ease of breathing.
Figure 22.17 Inspiration and Expiration illustrates that inspiration and expiration are the results of the expansion and contraction of the thoracic cavity. During a physical examination, the act of posterior chest expansion can be observed or measured to assess lung function and to identify abnormalities such as in cases of pneumonia, where chest radiographs may show lesions as opaque patches.