Neurovascular Supply of Bronchopulmonary Segments

Overview

Each bronchopulmonary segment receives its own dedicated bronchoarterial supply. Venous and lymphatic drainage, however, is intersegmental — shared between adjacent segments.

Arterial Supply

Pulmonary Arteries (Functional)

• Carry deoxygenated blood from the right ventricle to the lungs for gaseous exchange
• Branches of the pulmonary artery accompany the segmental bronchi and run dorsolateral to the bronchus centrally within each segment
• Each segment receives its own segmental artery — a branch of the lobar branch of the pulmonary artery
• Terminal capillaries lie in the walls of the alveoli and respiratory bronchioles

Bronchial Arteries (Nutritional)

• Carry oxygenated blood to supply the bronchial tree and pulmonary connective tissue (nutrient supply)
• Right side: 1 bronchial artery — arises from the 3rd right posterior intercostal artery (or from the superior left bronchial artery)
• Left side: 2 bronchial arteries — both arise from the descending thoracic aorta
  • Upper: opposite T5 vertebra
  • Lower: just below the left bronchus
• Precapillary anastomoses exist between bronchial and pulmonary arteries — these enlarge when either system is obstructed

Venous Drainage

Pulmonary Veins

• Drain oxygenated blood from the lungs to the left atrium
• Do not accompany the bronchi or pulmonary arteries
• Run in the intersegmental connective tissue planes — drain more than one segment
• Each segment has more than one pulmonary venous tributary; each tributary drains more than one segment
• Right superior pulmonary vein: drains right superior and middle lobes
• Right inferior pulmonary vein: drains right inferior lobe
• Left superior pulmonary vein: drains left superior lobe (including lingula)
• Left inferior pulmonary vein: drains left inferior lobe

Bronchial Veins

• Drain venous blood from the first and second divisions of the bronchi only
• Right bronchial vein: drains into the azygos vein
• Left bronchial vein: drains into the hemiazygos vein (accessory hemiazygos vein)
• The remainder of bronchial venous blood drains into the pulmonary veins

Lymphatic Drainage

Two sets of lymphatics, both draining ultimately into bronchopulmonary (hilar) nodes:

Set	Drains	Route
Superficial (subpleural) plexus	Peripheral lung tissue beneath visceral pleura	Pass around borders and fissure margins → bronchopulmonary nodes at hilum
Deep lymphatics	Bronchial tree, pulmonary vessels, connective tissue septa	Run centrally toward hilum → bronchopulmonary nodes

The superficial set has numerous valves; the deep set has few or none. Anastomoses between the two sets can open in disease (e.g., when deep vessels are obstructed).

Onward drainage: Bronchopulmonary (hilar) nodes → tracheobronchial nodes → bronchomediastinal trunk → thoracic duct (left) or right lymphatic duct (right)

Nerve Supply

Both parasympathetic and sympathetic nerves first form anterior and posterior pulmonary plexuses at the lung roots, then distribute along blood vessels and bronchi:

Type	Origin	Function
Parasympathetic	Vagus nerve	Motor to bronchial smooth muscle (bronchoconstriction); secretomotor to mucous glands; sensory (stretch reflex, cough reflex)
Sympathetic	T2–T5 sympathetic ganglia	Inhibitory to smooth muscle and glands (bronchodilatation)

Clinical note: Sympathomimetic drugs (e.g., adrenaline/epinephrine) mimic sympathetic action → bronchodilatation → used in bronchial asthma.

Surgical Significance of Intersegmental Veins

During segmental resection, the intersegmental veins must not be ligated — doing so would impair venous drainage of the adjacent healthy segments. The surgeon uses the intersegmental veins as guides to locate the planes between segments.