Lobes of the Right Lung

The right lung is divided into three distinct lobes: the superior (upper), middle, and inferior (lower) lobes. These lobes are separated by two fissures—the horizontal fissure and the oblique fissure. Each lobe is an anatomically and functionally distinct unit, containing its own bronchial, arterial, and venous branches. The division into lobes allows for more efficient organization of the lung’s airways and vascular supply, and facilitates segmental surgical resection if necessary.

Location

The right lung occupies the right hemithorax and lies adjacent to the thoracic wall, diaphragm, and mediastinum. It is slightly larger and heavier than the left lung but shorter due to the upward displacement by the liver. It also has a broader base and more vertical orientation of the bronchial tree.

External Surfaces

The right lung has three external surfaces:

• Costal surface: Convex and smooth, faces the internal surface of the rib cage
• Mediastinal surface: Concave, faces the heart and mediastinum; includes the hilum
• Diaphragmatic surface: Inferior surface resting on the diaphragm

Fissures of the Right Lung

Two fissures divide the right lung into its three lobes:

1. Oblique Fissure

• Separates the inferior lobe from both the superior and middle lobes
• Runs from the T2 vertebral level posteriorly to the 6th costochondral junction anteriorly

2. Horizontal Fissure

• Separates the superior lobe from the middle lobe
• Runs horizontally from the oblique fissure to the anterior border at the level of the 4th costal cartilage

Lobes of the Right Lung

1. Superior (Upper) Lobe

• Occupies the uppermost part of the right lung
• Situated anteriorly and superiorly, extending over the front of the mediastinum
• Receives air via the right superior lobar bronchus
• Contains three bronchopulmonary segments: apical, posterior, and anterior

2. Middle Lobe

• Lies between the superior and inferior lobes
• Bounded above by the horizontal fissure and below by the oblique fissure
• Receives air via the right middle lobar bronchus
• Contains two bronchopulmonary segments: lateral and medial

3. Inferior (Lower) Lobe

• Occupies the posteroinferior portion of the lung
• Largest of the three lobes
• Receives air via the right inferior lobar bronchus
• Contains five bronchopulmonary segments: superior, medial basal, anterior basal, lateral basal, and posterior basal

Bronchopulmonary Segments of the Right Lung

Each lobe is subdivided into bronchopulmonary segments, each supplied by a segmental (tertiary) bronchus and its accompanying artery:

Superior Lobe

1. Apical segment
2. Posterior segment
3. Anterior segment

Middle Lobe

1. Lateral segment
2. Medial segment

Inferior Lobe

1. Superior segment
2. Medial basal segment
3. Anterior basal segment
4. Lateral basal segment
5. Posterior basal segment

These segments are separated by connective tissue septa, making them surgically resectable without affecting adjacent segments.

Vascular Supply

Arterial Supply

• Pulmonary arteries: One branch to each bronchopulmonary segment, carrying deoxygenated blood
• Bronchial arteries: Arise from the thoracic aorta or intercostal arteries; supply lung tissue and bronchi

Venous Drainage

• Pulmonary veins: Carry oxygenated blood from multiple segments back to the left atrium
• Veins run in intersegmental planes

Innervation

• Parasympathetic fibers: From the vagus nerve (CN X); cause bronchoconstriction and glandular secretion
• Sympathetic fibers: From thoracic sympathetic trunk; cause bronchodilation
• Visceral afferents: Convey stretch and reflex sensations

Lymphatic Drainage

• Superficial (subpleural) and deep lymphatic plexuses
• Drain into pulmonary, bronchopulmonary (hilar), tracheobronchial, and paratracheal lymph nodes

Surface Anatomy

• Right lung reaches the apex above the clavicle (~2.5 cm superior)
• Inferior border reaches rib 6 anteriorly, rib 8 in the midaxillary line, and T10 posteriorly
• Horizontal fissure runs along the level of the 4th rib
• Oblique fissure follows the scapular line during expiration

Clinical Relevance

• Aspiration: The vertical orientation of the right main bronchus makes the right lung more prone to aspiration, especially into the lower lobe
• Lobectomy: Individual lobes can be surgically removed due to distinct vascular and bronchial supply
• Segmentectomy: Targeted removal of diseased bronchopulmonary segments without sacrificing entire lobes