- Lungs: paired principal organs of respiration, conical/pyramidal, in the thoracic cavity on either side of the mediastinum.
- Function: exchange of O2/CO2 between air and blood.
External Features
- Each lung shows an apex, a base, three borders and two surfaces.
trachea and lungs, anterior view Trachea and lungs, anterior view.
External features of the lung
Feature
Apex
- Key points
- Rounded; about 3 cm above 1st rib, 2.5 cm above medial clavicle; under cervical pleura and suprapleural membrane
Apex relations
- Key points
- Anterior: subclavian artery, internal thoracic artery, scalenus anterior. Posterior: 1st rib neck, sympathetic chain, T1 ventral ramus
Base
- Key points
- Semilunar, concave, on diaphragm; right on liver (more concave), left on spleen and stomach fundus
Anterior border
- Key points
- Thin; right straight, left has cardiac notch with lingula (superficial cardiac dullness)
Posterior border
- Key points
- Thick, rounded; spine of C7 to spine of T10
Inferior border
- Key points
- Semilunar; separates base from costal and medial surfaces
Costal surface
- Key points
- Convex; upper 6 ribs midclavicular line, 8 midaxillary line, 10 scapular line
Medial surface
- Key points
- Vertebral part (vertebral column, splanchnic nerves) plus mediastinal part bearing the hilum