Humans have five lung lobes in total: three in the right lung and two in the left. This asymmetry exists because the heart sits slightly left of center in the chest, taking up space that would otherwise belong to the left lung.
Right Lung: Three Lobes
The right lung is the larger of the two and contains three lobes: the upper lobe, the middle lobe, and the lower lobe. Two horizontal gaps called fissures separate them. Each lobe functions somewhat independently, with its own branch of the airway supplying it.
In terms of volume, the right upper lobe accounts for roughly 22% of total lung capacity, the middle lobe about 13%, and the right lower lobe around 19%. Together, the right lung handles a little more than half of your breathing capacity.
Left Lung: Two Lobes
The left lung has just two lobes: the superior (upper) and the inferior (lower). It’s longer and narrower than the right lung, and it has a curved indentation on its inner surface called the cardiac notch, a concave space carved out to accommodate the heart.
Tucked along the lower edge of that cardiac notch is a tongue-shaped projection called the lingula. It’s not a separate lobe, but it mirrors the structure and position of the right middle lobe. The left upper lobe (including the lingula) makes up about 28% of total lung capacity, while the left lower lobe contributes roughly 17%.
Segments Inside Each Lobe
Each lobe is further divided into smaller, self-contained units called bronchopulmonary segments. These are sections of lung tissue, each served by its own airway branch and blood supply. The right lung has 10 segments spread across its three lobes: three in the upper lobe, two in the middle lobe, and five in the lower lobe.
The left lung also has up to 10 segments, five in each lobe, but the actual count varies slightly from person to person. In many people, two pairs of segments in the left lung tend to fuse together, bringing the practical count down to eight. This is a normal variation, not an abnormality.
Segments matter most in a surgical context. When a tumor or diseased area is confined to one segment, surgeons can sometimes remove just that segment rather than an entire lobe, preserving more healthy lung tissue.
Anatomical Variations
A small number of people are born with an extra partial lobe in the right lung called an azygos lobe. It forms when a vein (the azygos vein) takes an unusual path during fetal development, pinching off a portion of the right upper lobe behind a fold of tissue. Studies of large patient groups put the prevalence at roughly 0.4% to just under 1%. An azygos lobe is almost always discovered incidentally on a chest scan and rarely causes any problems on its own.
Why Lobe Anatomy Matters
The five-lobe structure directly shapes how lung diseases are diagnosed and treated. Infections like pneumonia are often described by which lobe they affect, and imaging reports routinely localize findings to a specific lobe or segment. This precision helps doctors gauge severity and track whether a problem is spreading.
For lung cancer, lobe anatomy determines the surgical approach. Lobectomy, the removal of an entire lobe, remains the standard treatment for tumors that are larger or located near the center of a lobe. Recent trial data show that for small, early-stage tumors located near the lung’s outer edge, removing just a wedge or segment of tissue can produce similar survival outcomes while sparing more lung function. This tradeoff between removing enough tissue and preserving breathing capacity is possible precisely because each lobe and segment operates with its own airway and blood supply.
Because the lobes vary in size, losing one has different consequences depending on which one it is. Removing the small right middle lobe (about 13% of total capacity) has a much smaller impact on breathing than losing the left upper lobe (about 28%). Surgeons factor these volume differences into decisions about what a patient can tolerate.