Right lung

The right lung is the respiratory organ located in the right hemithorax, responsible for gas exchange. It is approximately one-third larger than the left lung, mainly due to the presence of the accessory lobe, and is attached to the mediastinum only by its hilus.

It is divided into several lobes, which differs among species, separated by interlobar fissures:

• Cranial lobe: the most anterior, its apex reaches the entrance of the thorax.

• Middle lobe: ventral, contributing to the V-shaped cardiac notch.

• Caudal lobe: the largest, resting on the diaphragm.

• Accessory lobe: dorsal to the caudal vena cava.

The right lung has a convex costal surface in contact with the ribs and a flat mediastinal surface bearing the cardiac impression. It is ventilated by the right main bronchus, and its vascularization includes the pulmonary arteries and pulmonary veins.

• In dogs, cats, and ruminants, the right lung is divided into four lobes: cranial, middle, caudal, and accessory.

• In horses, there is no middle lobe, so the right lung consists only of the cranial, caudal, and accessory lobes.

• Ruminants and pigs have a tracheal bronchus that directly supplies the right cranial lobe, which is absent in other species.

• In humans, the right lung is divided into three lobes: upper, middle, and lower.