Right Lung Segments

The right lung is divided into anatomically and functionally organized regions called bronchopulmonary segments. Each segment is supplied by its own segmental, or tertiary, bronchus and an accompanying segmental branch of the pulmonary artery.

The right lung is conventionally described as containing 10 bronchopulmonary segments. These segments are distributed among the superior, middle, and inferior lobes and form important units for anatomical localization, radiological interpretation, bronchoscopy, and pulmonary surgery.

Organization of the Right Lung

The right lung contains three lobes:

• Superior lobe
• Middle lobe
• Inferior lobe

The superior and middle lobes are separated by the horizontal fissure, while the oblique fissure separates the inferior lobe from the superior and middle lobes.

Bronchopulmonary Segments

A bronchopulmonary segment is a subdivision of a pulmonary lobe centered on a segmental bronchus and its accompanying pulmonary arterial branch.

Each segment represents a relatively independent bronchovascular unit. Connective tissue planes between neighboring segments allow individual segments to be identified and, when necessary, surgically removed while preserving adjacent lung tissue.

Basic Structure of a Segment

Bronchopulmonary segments are generally pyramidal or wedge-shaped. The apex of each segment is directed toward the hilum or root of the lung, while the broader base faces the pleural surface.

The segmental bronchus and pulmonary arterial branch generally occupy an intrasegmental position. Pulmonary veins typically run within intersegmental connective tissue planes and drain adjacent segments.

Right Superior Lobe

The superior lobe of the right lung is conventionally divided into three bronchopulmonary segments:

• Apical segment, S1
• Posterior segment, S2
• Anterior segment, S3

These segments are supplied by branches of the right superior lobar bronchus.

Apical Segment

The apical segment is designated S1. It occupies the superior portion of the right superior lobe and extends toward the apex of the lung.

It is supplied by the apical segmental bronchus, B1, and a corresponding segmental branch of the right pulmonary artery.

Posterior Segment

The posterior segment, designated S2, occupies the posterior region of the superior lobe.

It is supplied by the posterior segmental bronchus, B2, and an accompanying pulmonary arterial branch.

Anterior Segment

The anterior segment, designated S3, occupies much of the anterior region of the superior lobe.

It receives the anterior segmental bronchus, B3, together with its corresponding pulmonary arterial branch.

Segments of the Right Superior Lobe

Segment	Designation	General Location
Apical	S1	Superior and apical region
Posterior	S2	Posterior superior lobe
Anterior	S3	Anterior superior lobe

Right Middle Lobe

The middle lobe is the smallest lobe of the right lung and lies primarily on its anterior and lateral aspects.

It contains two bronchopulmonary segments, the lateral segment and the medial segment.

Lateral Segment

The lateral segment of the middle lobe is designated S4.

It occupies the more lateral portion of the middle lobe and is supplied by the lateral segmental bronchus, B4, and its corresponding pulmonary arterial branch.

Medial Segment

The medial segment of the middle lobe is designated S5.

It occupies the more medial portion of the middle lobe, close to the mediastinal surface and cardiac impression, and is supplied by the medial segmental bronchus, B5.

Segments of the Right Middle Lobe

Segment	Designation	General Location
Lateral	S4	Lateral middle lobe
Medial	S5	Medial middle lobe

Right Inferior Lobe

The inferior lobe is the largest lobe of the right lung and forms much of its posterior and inferior portions.

It is conventionally divided into five bronchopulmonary segments: one superior segment and four basal segments.

Superior Segment of the Inferior Lobe

The superior segment of the inferior lobe is designated S6.

It occupies the superior and posterior portion of the inferior lobe and is supplied by the superior segmental bronchus, B6.

The superior segmental bronchus typically arises before the lower lobe bronchus continues into the basal bronchial divisions.

Basal Segments

Inferior to S6, the right inferior lobe contains four principal basal segments. These occupy the lower portion of the lung and are organized around branches of the basal bronchial trunk.

The basal segments are medial basal, anterior basal, lateral basal, and posterior basal.

Medial Basal Segment

The medial basal segment is designated S7.

It occupies the medial part of the inferior lobe base and is supplied by the medial basal segmental bronchus, B7.

Anterior Basal Segment

The anterior basal segment, designated S8, occupies the anterior portion of the basal region.

It is supplied by the anterior basal segmental bronchus, B8, and its accompanying pulmonary arterial branch.

Lateral Basal Segment

The lateral basal segment is designated S9.

It occupies the lateral portion of the inferior lobe base and receives the lateral basal segmental bronchus, B9.

Posterior Basal Segment

The posterior basal segment, designated S10, occupies the posterior basal portion of the inferior lobe.

It is supplied by the posterior basal segmental bronchus, B10, and represents an important dependent region of the lung in many body positions.

Segments of the Right Inferior Lobe

Segment	Designation	General Location
Superior	S6	Superior posterior inferior lobe
Medial basal	S7	Medial basal region
Anterior basal	S8	Anterior basal region
Lateral basal	S9	Lateral basal region
Posterior basal	S10	Posterior basal region

Complete Segmental Arrangement

Lobe	Segment	Designation
Superior	Apical	S1
Superior	Posterior	S2
Superior	Anterior	S3
Middle	Lateral	S4
Middle	Medial	S5
Inferior	Superior	S6
Inferior	Medial basal	S7
Inferior	Anterior basal	S8
Inferior	Lateral basal	S9
Inferior	Posterior basal	S10

Segmental Bronchi

Each bronchopulmonary segment is ventilated by a segmental bronchus, also known as a tertiary bronchus.

These bronchi arise through sequential branching of the right main bronchus into lobar bronchi and subsequently into segmental bronchi.

Right Main Bronchus

The right main bronchus is generally wider, shorter, and more vertical than the left main bronchus.

It gives rise to bronchi supplying the superior, middle, and inferior lobes. The lobar bronchi subsequently divide into segmental bronchi that correspond to the individual bronchopulmonary segments.

Superior Lobar Bronchus

The right superior lobar bronchus supplies the superior lobe and divides into segmental branches for S1, S2, and S3.

At the hilum, the superior lobar bronchus has a characteristic relationship to the right pulmonary artery and is often described as the eparterial bronchus because it arises above the level of the pulmonary artery.

Bronchus Intermedius

After the superior lobar bronchus arises, the right main bronchus continues as the bronchus intermedius.

The bronchus intermedius subsequently gives rise to the middle and inferior lobar bronchi, which supply the middle and inferior lobes respectively.

Pulmonary Arterial Supply

Each bronchopulmonary segment receives a corresponding segmental branch of the pulmonary artery.

Segmental pulmonary arterial branches generally accompany segmental bronchi and occupy relatively central positions within their respective segments.

Pulmonary Venous Drainage

Pulmonary venous drainage does not follow the same segment-centered pattern as the bronchi and pulmonary arteries.

Tributaries of the pulmonary veins commonly course within intersegmental planes, receiving blood from neighboring bronchopulmonary segments before ultimately draining toward the pulmonary veins.

Intrasegmental and Intersegmental Structures

Structure	Relationship
Segmental bronchus	Intrasegmental
Segmental pulmonary artery	Intrasegmental
Pulmonary venous tributaries	Primarily intersegmental

Intersegmental Planes

Adjacent bronchopulmonary segments are separated by connective tissue planes to varying degrees.

These planes are important surgically because they help define boundaries between segments and allow selected diseased segments to be removed while preserving neighboring functional lung tissue.

Comparison with the Left Lung

The right and left lungs share the same basic principle of bronchopulmonary segmentation, but their segmental organization differs because of differences in lobar anatomy and bronchial branching.

Feature	Right Lung	Left Lung
Lobes	3	2
Common segment count	10	Approximately 8 to 10
Middle lobe	Present	Absent
Lingula	Absent	Present
S1 and S2	Usually separate	Frequently combined as S1+S2
S7 and S8	Usually separate	May be combined as S7+S8

Right Middle Lobe and Lingula

The right middle lobe is frequently compared with the lingula of the left lung. Both contain two commonly recognized bronchopulmonary segments and occupy relatively anterior positions.

They are not identical structures, however. The right middle lobe is a distinct lobe separated by fissures, whereas the lingula is part of the left superior lobe.

Anatomical Variation

Although the 10-segment model is widely used, bronchial and vascular branching patterns vary between individuals.

Segmental bronchi may arise through shared trunks, divide differently, or supply territories that vary from the conventional pattern. Detailed preoperative imaging may therefore be required when precise segmental anatomy is clinically important.

Radiological Anatomy

Bronchopulmonary segment anatomy provides a framework for localizing pulmonary abnormalities on computed tomography and other imaging studies.

A lesion can be described according to its lobe and segment, allowing more precise communication of its relationship to bronchi, pulmonary vessels, fissures, and pleural surfaces.

Bronchoscopy

During bronchoscopy, the lobar and segmental bronchial openings provide anatomical landmarks for navigating the tracheobronchial tree.

Recognition of individual segmental bronchi allows clinicians to target specific pulmonary regions for inspection, bronchoalveolar lavage, biopsy, secretion removal, or other procedures.

Segmentectomy

A segmentectomy is an anatomical surgical resection of one or more bronchopulmonary segments.

Segmentectomy is possible because individual segments possess relatively independent bronchial and pulmonary arterial supplies and can be separated along intersegmental planes.

Surgical Importance of Pulmonary Veins

Intersegmental pulmonary veins are important landmarks during segmental lung surgery.

Because these vessels often define boundaries between neighboring segments, identifying and preserving appropriate venous drainage can help guide anatomical segmentectomy.

Aspiration and the Right Lung

The relatively wider and more vertical course of the right main bronchus makes the right bronchial tree an important route for aspirated material.

The eventual location of aspirated material depends on body position, gravity, and bronchial branching. Knowledge of segmental anatomy helps localize aspiration-related abnormalities.

Dependent Segments

Different bronchopulmonary segments become dependent according to body position. In a recumbent individual, posterior portions of the upper lobes and superior portions of the lower lobes may become important dependent regions.

In an upright individual, basal segments of the inferior lobes are more dependent. These relationships are relevant to aspiration and the distribution of some pulmonary infections.

Localization of Pulmonary Disease

Infection, bronchial obstruction, tumors, aspiration, atelectasis, and other pulmonary abnormalities may involve individual bronchopulmonary segments or groups of segments.

Segment-based localization therefore provides greater anatomical precision than describing disease solely by pulmonary lobe.

Segmental Organization

1. The right main bronchus enters the right lung.
2. The superior lobar bronchus supplies the superior lobe.
3. The bronchus intermedius continues toward the middle and inferior lobes.
4. Lobar bronchi divide into segmental bronchi.
5. Each segmental bronchus supplies a bronchopulmonary segment.
6. A corresponding pulmonary arterial branch accompanies each segmental bronchus.
7. Pulmonary venous tributaries generally course between neighboring segments.
8. The superior lobe contains S1, S2, and S3.
9. The middle lobe contains S4 and S5.
10. The inferior lobe contains S6 through S10.

Key Anatomical Relationships

• The right lung contains three lobes.
• The horizontal fissure separates the superior and middle lobes.
• The oblique fissure separates the inferior lobe from the superior and middle lobes.
• The right lung is conventionally divided into 10 bronchopulmonary segments.
• S1 is the apical segment.
• S2 is the posterior segment.
• S3 is the anterior segment.
• S4 is the lateral segment of the middle lobe.
• S5 is the medial segment of the middle lobe.
• S6 is the superior segment of the inferior lobe.
• S7 is the medial basal segment.
• S8 is the anterior basal segment.
• S9 is the lateral basal segment.
• S10 is the posterior basal segment.
• Segmental bronchi and pulmonary arterial branches are intrasegmental.
• Pulmonary venous tributaries commonly occupy intersegmental planes.
• Segmental anatomy provides the structural basis for pulmonary segmentectomy.

Clinical Importance

The bronchopulmonary segments of the right lung provide a detailed anatomical framework for understanding the internal organization of pulmonary tissue. Each segment is centered on a segmental bronchus and pulmonary arterial branch, while pulmonary venous tributaries generally pass between neighboring segments.

The conventional arrangement of 10 segments allows pulmonary abnormalities to be localized with considerable precision. Segmental anatomy is particularly important in chest imaging, bronchoscopy, evaluation of aspiration, localization of infection or tumors, and planning of anatomical lung resections.

Understanding right lung segments provides the anatomical foundation for studying segmental bronchi, pulmonary arterial branches, intersegmental veins, lobar anatomy, aspiration patterns, bronchoscopy, pulmonary segmentectomy, and segmental localization of respiratory disease.