Left lower lobe

Last revised by Melad Syed on 12 Jun 2021

The left lower lobe (LLL) is one of two lobes in the left lung. It is separated from the left upper lobe by the left oblique fissure and subdivided into four bronchopulmonary segments.

    The LLL lies in the posterior and lower aspect of the left hemithorax and contains four bronchopulmonary 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 left lower lobe bronchus arises as the inferiorly angled continuation of the left main bronchus to traverse the left hilum into the LLL.

    The LLL is separated from the left upper lobe posterosuperiorly by the left oblique fissure.

    Like all the lobes of the lung, the LLL has dual arterial supply:

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

    Left bronchial veins drain into the accessory hemiazygos vein or the left superior intercostal 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.

    • parasympathetic fibers from the vagus nerve (CN X)
    • sympathetic fibers from the paravertebral sympathetic trunks

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    Cases and figures

  • Figure 1: left sided bronchi
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  • Figure 2: Bronchopulmonary Segments: annotated CT
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  • Figure 3: normal chest x-ray - lobes (illustration)
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  • Figure 4: normal chest x-ray - lobes (illustration)
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