Anatomical, functional, surgical units of lung. Each has own segmental bronchus + segmental pulmonary artery branch → diseased segments can be removed, healthy lung preserved.

Core: segmental bronchus + segmental pulmonary artery = central supply; pulmonary veins run between segments

Definition

Pyramidal lung lobe subdivision; aerated by tertiary/segmental bronchus; supplied by segmental pulmonary artery branch

Features

Not a true bronchovascular segment — no separate vein; pulmonary veins run intersegmental, drain adjacent segments

Bronchial Tree

• Trachea bifurcates at carina, sternal angle level, ~T4/T5

Right vs Left Principal Bronchus

Right superior lobar bronchus = eparterial (arises above right pulmonary artery); others hyparterial

Right Lung Segments (10)

Upper lobe: S1 Apical, S2 Posterior, S3 Anterior

Middle lobe: S4 Lateral, S5 Medial

Lower lobe: S6 Superior/apical, S7 Medial basal/cardiac, S8 Anterior basal, S9 Lateral basal, S10 Posterior basal

Left Lung Segments

• 2 lobes; texts list 10, but apicoposterior + anteromedial basal segments often combined clinically → 8–9 named segments

Upper division: S1 Apical, S2 Posterior, S3 Anterior Lingular division: S4 Superior lingular, S5 Inferior lingular (lingula = functional right middle lobe equivalent)

Lower lobe: S6 Superior/apical, S7 Medial basal (often combined with S8), S8 Anterior basal, S9 Lateral basal, S10 Posterior basal

Left lower lobe: medial basal often small/combined with anterior basal as anteromedial basal bronchus

Right vs Left Equivalents

Neurovascular Supply

Pulmonary arteries — deoxygenated blood for gas exchange; accompany segmental bronchi centrally

Bronchial arteries — nutritional supply

Pulmonary veins — oxygenated blood to LA; do NOT accompany segmental bronchi; run intersegmental; drain >1 segment → guides for segmental resection

Lymphatics: superficial subpleural plexus + deep plexus → bronchopulmonary/hilar nodes → tracheobronchial nodes → bronchomediastinal trunk

Nerve supply — anterior + posterior pulmonary plexuses

Postural Drainage

• Affected segment placed uppermost, bronchus directed downward → secretions move to carina, coughed out

Uses: bronchiectasis, CF, lung abscess, chronic suppurative disease, postop atelectasis

Applied Anatomy

Foreign body aspiration — more common right principal bronchus (shorter, wider, more vertical)

Aspiration pneumonia — bedridden/unconscious: commonly enters superior segment of lower lobe, especially right

Segmental resection — basis: own bronchus + pulmonary artery; intersegmental veins mark planes, preserved when possible

• Indications: bronchiectasis, TB, benign tumour, localised chronic infection

Bronchoscopy — landmarks: carina, lobar bronchi, segmental openings; carinal widening → subcarinal node enlargement (malignancy, TB, sarcoidosis, lymphoma)

Bronchiectasis — permanent bronchial dilatation; commonly basal segments of lower lobes; chronic cough, foul sputum; managed partly by postural drainage

Tuberculosis

Bronchopulmonary segments are the anatomical, functional, and surgical units of the lung. Each segment has its own segmental bronchus and branch of pulmonary artery, so diseased segments can be removed while preserving healthy lung.

The core idea:

Segmental bronchus + segmental pulmonary artery = central supply; pulmonary veins run between segments.

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Definition

A bronchopulmonary segment is a well-defined pyramidal subdivision of a lung lobe, aerated by a tertiary / segmental bronchus and supplied by a segmental branch of the pulmonary artery.

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Characteristic Features

The segment is not a true bronchovascular segment because it does not have its own separate vein. Pulmonary veins run in intersegmental planes and drain adjacent segments.

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Bronchial Tree

The trachea bifurcates at the carina at the level of the sternal angle, around T4/T5.

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Right and Left Principal Bronchi

The right superior lobar bronchus is called the eparterial bronchus because it arises above the right pulmonary artery. Other lobar bronchi are hyparterial.

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Right Lung Segments

The right lung has 3 lobes and classically 10 segments.

Upper Lobe

Middle Lobe

Lower Lobe

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Left Lung Segments

The left lung has 2 lobes. Many anatomy texts list 10 segments, but clinically and radiologically the left apicoposterior segments and anteromedial basal segments may be combined, giving 8 or 9 named segments.

Upper Lobe

Upper division:

Lingular division:

The lingula corresponds functionally to the right middle lobe.

Lower Lobe

In the left lower lobe, the medial basal bronchus is often small or arises with the anterior basal bronchus as an anteromedial basal bronchus.

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Right vs Left Segment Equivalents

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Neurovascular Supply

Pulmonary Arteries

• Carry deoxygenated blood for gas exchange.
• Branches accompany segmental bronchi.
• Run centrally within segments.
• Each segment receives a segmental pulmonary arterial branch.

Bronchial Arteries

Bronchial arteries provide nutritional blood to bronchi and lung connective tissue.

Pulmonary Veins

• Carry oxygenated blood to the left atrium.
• Do not accompany segmental bronchi.
• Run in intersegmental connective tissue planes.
• Drain more than one segment.

This is why intersegmental veins are guides during segmental resection.

Lymphatics

Further drainage:

Bronchopulmonary nodes → Tracheobronchial nodes → Bronchomediastinal trunk

Nerve Supply

Nerves form anterior and posterior pulmonary plexuses.

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Postural Drainage

Postural drainage uses gravity to drain secretions from affected segments towards larger bronchi.

Principle:

• The affected segment is placed uppermost.
• Its bronchus is directed downward.
• Secretions move towards the carina and are coughed out.

Dependent Segments

Important Uses

• Bronchiectasis
• Cystic fibrosis
• Lung abscess
• Chronic suppurative lung disease
• Postoperative atelectasis

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Applied Anatomy

Foreign Body Aspiration

Foreign bodies enter the right principal bronchus more commonly because it is shorter, wider, and more vertical.

Aspiration Pneumonia

In bedridden or unconscious patients, aspirated material commonly enters the superior segment of the lower lobe, especially on the right.

Segmental Resection

Basis:

• Each segment has its own bronchus and pulmonary artery.
• Segmental veins mark intersegmental planes.
• Disease limited to one segment can be removed conservatively.

Important surgical point:

• Intersegmental veins should be preserved when possible because they drain adjacent healthy segments.

Common indications:

• Bronchiectasis
• Tuberculosis
• Benign tumour
• Localised chronic infection

Bronchoscopy

Bronchoscopy visualises the bronchial tree down to segmental bronchi.

Important landmarks:

• Carina
• Lobar bronchi
• Segmental bronchial openings

Widening of the carina suggests subcarinal lymph node enlargement due to malignancy, tuberculosis, sarcoidosis, or lymphoma.

Bronchiectasis

• Permanent pathological dilatation of bronchi
• Commonly affects basal segments of lower lobes
• Produces chronic cough and foul-smelling sputum
• Managed partly by postural drainage

Tuberculosis

High oxygen tension favours reactivation disease in apical regions.

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