Bronchopulmonary Lymph Nodes

The bronchopulmonary lymph nodes, commonly referred to as hilar lymph nodes, are a key group of thoracic lymph nodes located at the hilum of each lung. These nodes serve as a major conduit for lymphatic drainage from the lungs and are situated where the bronchi, blood vessels, and nerves enter and exit the lung. They play a critical role in filtering lymph from pulmonary tissues before it progresses toward the central mediastinal nodes.

Location

• Found at the hilum of the lungs, surrounding the main bronchi and pulmonary vessels
• Present on both the right and left sides, embedded within the connective tissue of the root of the lung

Afferent Drainage

The bronchopulmonary nodes receive lymph from:

• Pulmonary (intrapulmonary) lymph nodes located within the lung parenchyma
• Peripheral lung tissue including alveolar and bronchiolar regions
• Visceral pleura and subpleural lymphatics

Efferent Drainage

• Drains lymph into the inferior tracheobronchial (carinal) lymph nodes
• Also connects with superior tracheobronchial nodes and then into paratracheal lymph nodes
• Eventually enters the bronchomediastinal lymph trunks, which flow into the thoracic duct or right lymphatic duct

Function

• Filters lymph from the lungs before it enters the mediastinal drainage system
• Acts as a barrier against pathogens and malignant cells within the lungs
• Initiates local immune responses by exposing lymph to antigen-presenting cells

Relations

• Medial: Main bronchi and pulmonary arteries
• Lateral: Lung parenchyma
• Anterior: Pulmonary veins
• Posterior: Pulmonary ligament and bronchial arteries

Histological Features

• Composed of dense lymphoid tissue with germinal centers
• Contains macrophages, dendritic cells, and lymphocytes
• Encapsulated with afferent lymphatic vessels entering and efferent vessels exiting the node

Clinical Significance

• Lymphadenopathy: Common site of node enlargement in lung infections, sarcoidosis, and metastasis
• Lung cancer staging: Involvement of hilar nodes is classified as N1 disease in TNM staging
• Visible on imaging: Frequently assessed in chest CT and PET scans
• Biopsy target: In suspected malignancy, may be sampled via EBUS or mediastinoscopy

Topographic Summary

• Location: At the hilum of each lung, around main bronchi
• Afferents: From intrapulmonary nodes and lung parenchyma
• Efferents: To tracheobronchial and paratracheal lymph nodes
• Function: Filter lymph from lungs; important in infection and cancer pathways