Right middle lobe

Dr Craig Hacking et al.

The right middle lobe (RML) or simply the middle lobe is one of three lobes in the right lung. It is separated from the right upper lobe above by the horizontal fissure and the right lower lobe below by the right oblique fissure and is subdivided into two bronchopulmonary segments.

    Location and structure

    The right middle lobe lies in the lower anterior aspect of the right hemithorax and contains two bronchopulmonary segments:

    This is easy to remember as the middle lobe has medial and lateral segments.

    Like all the pulmonary lobes, it is lined by visceral pleura which reflects at the pulmonary hilum where it is continuous with the parietal pleura. The right middle lobe bronchus arises from the lateral wall of the bronchus intermedius to traverses the right hilum into the right middle lobe.

    The right middle lobe is separated from the right lower lobe below and posteriorly by the oblique fissure and from the right upper lobe above by the horizontal fissure.

    Arterial supply

    Like all the lobes of the lung, the right middle lobe has dual arterial supply:

    Venous drainage

    Venous drainage of newly oxygenated blood is via the right inferior pulmonary vein into the left atrium.

    Right bronchial veins drain into the azygos vein.

    The superficial subpleural lymphatic plexus drains the lung parenchyma and visceral pleura to the bronchopulmonary (hilar) lymph nodes in the hilum.

    The deep bronchopulmonary lymphatic plexus (in the bronchial submucosa and peribronchial interstitium) drains the root of the lung to hilar lymph nodes in the hilum.

    The hilar lymph nodes then drain to the tracheobronchial lymph nodes.

    Thoracic anatomy
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    Article information

    rID: 38909
    System: Chest
    Section: Anatomy
    Tags: refs, cases
    Synonyms or Alternate Spellings:
    • Middle lobe
    • RML
    • ML

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    Cases and figures

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    Figure 1: right sided bronchi
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    Figure 2: Bronchopulmonary Segments: annotated CT
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