cardiac notch
The cardiac notch is only found on the left lung, which makes sense since the heart is located on the left side of the mediastinum. The horizontal fissure is a deep groove that separates the middle lobe from the upper lobe of the right lung. The left lung does not have a horizontal fissure. The oblique fissure is found in both lungs. It separates the upper lobe from the lower lobe in both lungs and the middle lobe from the lower lobe in the right lung. Both lungs also have a superior lobar bronchus leading to their superior lobes. Finally, the right lung has three lobes while the left lung has two lobes.