Topography
Each lung fills its pleural cavity, from the cupula of the pleura, which projects just past the first rib, to the diaphragm. Between them lies the mediastinum with the heart, trachea and esophagus. The basal border follows a line running roughly from the costochondral junction of the 6th rib to the 11th intercostal space next to the spine; caudal to that line the costodiaphragmatic recess of the pleura holds no lung.
Lobes
- Left lung: cranial lobe (with cranial and caudal parts) and caudal lobe.
- Right lung: cranial, middle, caudal and accessory lobes. The accessory lobe sits in the mediastinal recess around the caudal vena cava.
- Cardiac notch: on the right side, between the cranial and middle lobes (ventral 4th–5th intercostal space), the pericardium touches the chest wall. This is the usual site for pericardiocentesis.
Clinical relevance
- Thoracic radiography: three views (right lateral, left lateral and ventrodorsal) are taken, especially when looking for pulmonary metastases.
- Aspiration pneumonia: typically affects the cranioventral lobes, above all the right middle lobe.
- Lung lobe torsion: more frequent in deep-chested breeds (right middle lobe) and in pugs (left cranial lobe).
- Pneumothorax and pleural effusion: air or fluid separates the lung from the chest wall and diaphragm.
3D model
The caudal half of both lungs comes from the CT (including the diaphragmatic surface); the cranial half was modelled by extending that cross-section to the thoracic inlet along the atlas rib cage, and the space for the heart was carved out. The lobes are not separated.