SURFACE ANATOMY

Apex: lung apex and pleural cupola extend about 2–3 cm above the medial third of the clavicle into the root of the neck. 

Anterior margin (right): follows the right side of the sternum from about the 2nd to the 4th costal cartilages then slopes laterally to reach the 6th right costal cartilage. 

Anterior margin (left): similar but deviates laterally to form the cardiac notch and reaches approximately 3 cm lateral to the left sternal edge at the upper margin of the 6th costal cartilage (the cardiac notch produces the lingula). 

Inferior margins (costal landmark lines)

Mid-clavicular line: inferior border of lung at 6th rib (pleural reflection ~2 ribs lower). 

Mid-axillary line: inferior border of lung at 8th rib. 

Posteriorly (paravertebral): inferior border reaches roughly the 10th rib/vertebral level. 

Note: the parietal pleura extends ~2 ribs lower than the lung at these points, creating the costodiaphragmatic recess.