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Bronchi

Anatomy and Physiology · NLM MeSH · updated 2026-10-31 · version 1

Citations verified against PubMedNot yet clinician-reviewed10 referencesApproximately 6 min read

The larger air passages of the lungs arising from the terminal bifurcation of the trachea.

Table of Contents

1. Definition2. Research landscape3. Reading the evidence4. Open-access studies5. Key reviews6. References7. About this article

Definition and research guide

This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.

Content available: 4 complete abstracts (1,146 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.

Definition

The larger air passages of the lungs arising from the terminal bifurcation of the trachea. They include the largest two primary bronchi which branch out into secondary bronchi, and tertiary bronchi which extend into bronchioles and pulmonary alveoli.

Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.

Also known as: Bronchus; Primary Bronchi; Bronchi, Primary; Bronchus, Primary; Primary Bronchus; Secondary Bronchi; Bronchi, Secondary; Bronchus, Secondary.

Where it fits in the MeSH classification

Broader topics
Lung
Narrower topics
Bronchioles
See also
Bronchodilator Agents; Bronchography; Bronchoscopy; Bronchoconstrictor Agents

Related concepts

  • Trachea
  • Bronchioles
  • Pulmonary Alveoli

Research landscape

PubMed indexes 44,230 records tagged with the MeSH heading “Bronchi” (counts retrieved 2026-10-31). 2,968 of them (6.7%) were published from 2020 onward, and the busiest period so far is through 1999 with 27,513 records.

Reviews account for 2,923 records (6.6%) and meta-analyses for 33. Randomized controlled trials number 720 (1.6%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.

PubMed records by publication periodthrough 1999: 27,513 records; 2000-2009: 6,956 records; 2010-2019: 6,793 records; 2020 onward: 2,968 records27,513through 19996,9562000-20096,7932010-20192,9682020 onward
Records in PubMed indexed with this heading, by publication period. Real counts from NCBI E-utilities; the final period covers only part of the current year. Volume reflects how much has been published, not how strong the evidence is.
Show the data
PeriodRecords
through 199927,513
2000-20096,956
2010-20196,793
2020 onward2,968
Share of records by publication typeReviews: 6.6 percent; Meta-analyses: 0.1 percent; Randomized controlled trials: 1.6 percentReviews6.6% (2,923)Meta-analyses0.1% (33)Randomized controlled trials1.6% (720)
Share of all PubMed records on this heading that carry each publication type. Types overlap with other records, so the shares do not sum to 100%.
Publication-type chart data
Publication types among 44,230 PubMed records
TypeRecordsShare
Reviews2,9236.6%
Meta-analyses330.1%
Randomized controlled trials7201.6%

Method: PubMed query "Bronchi"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.

Reading the evidence in anatomy and physiology

Anatomy describes how body structures are built and physiology describes how they normally work, so most findings here are descriptive or mechanistic rather than evidence about treatment. Much of what is known comes from dissection, imaging, tissue studies and experiments in animals, and measurements in healthy volunteers can differ from those in people with disease or at different ages. Normal ranges vary between individuals and populations. Check whether a result was measured in people or in another species, the age and health of the participants, and the method used.

Evidence from open-access studies

These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.

Study comparison — selected abstracts, not a systematic review
Study / authorsYearSource label / designEurope PMC citationsLicence / source
Resveratrol and Pterostilbene Inhibit SARS-CoV-2 Replication in Air-Liquid Interface Cultured Human Primary Bronchial Epithelial Cells
Ter Ellen BM, Dinesh Kumar N, Bouma EM, Troost B, van de Pol DPI, van der Ende-Metselaar HH, et al.
2021Research article
Design not recorded in structured metadata
60cc by
PMID 34372541 · DOI · PMC8309965
Ferrostatin-1 and 3-Methyladenine Ameliorate Ferroptosis in OVA-Induced Asthma Model and in IL-13-Challenged BEAS-2B Cells
Yang N, Shang Y
2022Research article
Design not recorded in structured metadata
57cc by
PMID 35154576 · DOI · PMC8837457
Deep learning for anatomical interpretation of video bronchoscopy images
Yoo JY, Kang SY, Park JS, Cho YJ, Park SY, Yoon HI, et al.
2021Research article
Design not recorded in structured metadata
33cc by
PMID 34887497 · DOI · PMC8660867
Epithelial stem cells from human small bronchi offer a potential for therapy of idiopathic pulmonary fibrosis
Liu Z, Zheng Q, Li Z, Huang M, Zhong C, Yu R, et al.
2025Research article
Design not recorded in structured metadata
14cc by
PMID 39753035 · DOI · PMC11754162

Resveratrol and Pterostilbene Inhibit SARS-CoV-2 Replication in Air-Liquid Interface Cultured Human Primary Bronchial Epithelial Cells [1]

Research article Ter Ellen BM, Dinesh Kumar N, Bouma EM, Troost B, van de Pol DPI, van der Ende-Metselaar HH, et al. · · 2021 · cited 60 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
The current COVID-19 pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has an enormous impact on human health and economy.
Closing excerpt
Because these results represent laboratory findings in cells, we advocate evaluation of these compounds in clinical trials before statements are made whether these drugs are advantageous for COVID-19 treatment.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (229 words)

The current COVID-19 pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has an enormous impact on human health and economy. In search for therapeutic options, researchers have proposed resveratrol, a food supplement with known antiviral, anti-inflammatory, and antioxidant properties as an advantageous antiviral therapy for SARS-CoV-2 infection. Here, we provide evidence that both resveratrol and its metabolically more stable structural analog, pterostilbene, exhibit potent antiviral properties against SARS-CoV-2 in vitro. First, we show that resveratrol and pterostilbene antiviral activity in African green monkey kidney cells. Both compounds actively inhibit virus replication within infected cells as reduced virus progeny production was observed when the compound was added at post-inoculation conditions. Without replenishment of the compound, antiviral activity was observed up to roughly five rounds of replication, demonstrating the long-lasting effect of these compounds. Second, as the upper respiratory tract represents the initial site of SARS-CoV-2 replication, we also assessed antiviral activity in air-liquid interface (ALI) cultured human primary bronchial epithelial cells, isolated from healthy volunteers. Resveratrol and pterostilbene showed a strong antiviral effect in these cells up to 48 h post-infection. Collectively, our data indicate that resveratrol and pterostilbene are promising antiviral compounds to inhibit SARS-CoV-2 infection. Because these results represent laboratory findings in cells, we advocate evaluation of these compounds in clinical trials before statements are made whether these drugs are advantageous for COVID-19 treatment.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 34372541 · DOI · PMC8309965

Ferrostatin-1 and 3-Methyladenine Ameliorate Ferroptosis in OVA-Induced Asthma Model and in IL-13-Challenged BEAS-2B Cells [2]

Research article Yang N, Shang Y · · 2022 · cited 57 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
Ferroptosis was reported to be involved in the occurrence and development of asthma.
Closing excerpt
Collectively, Ferr-1 and 3-MA ameliorated asthma in vivo and in vitro through inhibiting ferroptosis, providing a new strategy for the clinical treatment of asthma.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (210 words)

Ferroptosis was reported to be involved in the occurrence and development of asthma. However, the potential mechanism underlying the role of ferroptosis in asthma remains unclear. In this study, we established the mouse asthma model following the ovalbumin (OVA) method in C57BL/6 mice and the cell model with IL-13 induction in bronchial epithelial cells (BEAS-2B cells). Treatment of ferrostatin-1 (Ferr-1) and 3-methyladenine (3-MA) decreased iron deposition in IL-13-induced BEAS-2B cells and lung tissues of asthma mice, opposite to that in bronchoalveolar lavage fluid (BALF). Meanwhile, excessive lipid peroxidation asthma model in vivo and in vitro was alleviated by Ferr-1 or 3-MA treatment. In addition, Ferr-1 and 3-MA inhibited the expression of LC-3 in these cells and lung tissues of mice. Moreover, Ferr-1 and 3-MA also suppressed the production of inflammatory cytokines (IL-1β, IL-6, and TNF-α) and oxidative stress factors (ROS and MDA), while promoting the level of SOD, in vivo and in vitro. Furthermore, application of Ferr-1 exhibited a greater inhibitory effect on iron release and lipid peroxidation in IL-13-induced BEAS-2B cells and asthma mice than 3-MA, accompanied with a weaker effect on ferritinophagy than 3-MA. Collectively, Ferr-1 and 3-MA ameliorated asthma in vivo and in vitro through inhibiting ferroptosis, providing a new strategy for the clinical treatment of asthma.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 35154576 · DOI · PMC8837457

Deep learning for anatomical interpretation of video bronchoscopy images [3]

Research article Yoo JY, Kang SY, Park JS, Cho YJ, Park SY, Yoon HI, et al. · · 2021 · cited 33 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
Anesthesiologists commonly use video bronchoscopy to facilitate intubation or confirm the location of the endotracheal tube; however, depth and orientation in the bronchial tree can often be confused because anesthesiologists cannot trace the airway from the oropharynx when it is performed using an endotracheal tube.
Closing excerpt
This model can be a basis for designing a clinical decision support system with video bronchoscopy.
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (386 words)

Anesthesiologists commonly use video bronchoscopy to facilitate intubation or confirm the location of the endotracheal tube; however, depth and orientation in the bronchial tree can often be confused because anesthesiologists cannot trace the airway from the oropharynx when it is performed using an endotracheal tube. Moreover, the decubitus position is often used in certain surgeries. Although it occurs rarely, the misinterpretation of tube location can cause accidental extubation or endobronchial intubation, which can lead to hyperinflation. Thus, video bronchoscopy with a decision supporting system using artificial intelligence would be useful in the anesthesiologic process. In this study, we aimed to develop an artificial intelligence model robust to rotation and covering using video bronchoscopy images. We collected video bronchoscopic images from an institutional database. Collected images were automatically labeled by an optical character recognition engine as the carina and left/right main bronchus. Except 180 images for the evaluation dataset, 80% were randomly allocated to the training dataset. The remaining images were assigned to the validation and test datasets in a 7:3 ratio. Random image rotation and circular cropping were applied. Ten kinds of pretrained models with < 25 million parameters were trained on the training and validation datasets. The model showing the best prediction accuracy for the test dataset was selected as the final model. Six human experts reviewed the evaluation dataset for the inference of anatomical locations to compare its performance with that of the final model. In the experiments, 8688 images were prepared and assigned to the evaluation (180), training (6806), validation (1191), and test (511) datasets. The EfficientNetB1 model showed the highest accuracy (0.86) and was selected as the final model. For the evaluation dataset, the final model showed better performance (accuracy, 0.84) than almost all human experts (0.38, 0.44, 0.51, 0.68, and 0.63), and only the most-experienced pulmonologist showed performance comparable (0.82) with that of the final model. The performance of human experts was generally proportional to their experiences. The performance difference between anesthesiologists and pulmonologists was marked in discrimination of the right main bronchus. Using bronchoscopic images, our model could distinguish anatomical locations among the carina and both main bronchi under random rotation and covering. The performance was comparable with that of the most-experienced human expert. This model can be a basis for designing a clinical decision support system with video bronchoscopy.

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 34887497 · DOI · PMC8660867

Epithelial stem cells from human small bronchi offer a potential for therapy of idiopathic pulmonary fibrosis [4]

Research article Liu Z, Zheng Q, Li Z, Huang M, Zhong C, Yu R, et al. · · 2025 · cited 14 times (Europe PMC)

Abstract reading summary — source excerpts
Opening excerpt
BackgroundIdiopathic pulmonary fibrosis (IPF) is a fibrosing interstitial pneumonia with restrictive ventilation.
Closing excerpt
FundingNational Natural Science Foundation of China (82430001, 81930001, and 81900059), Shanghai Shenkang Hospital Development Center (SHDC2020CR3063B), Department of Science and Technology of Shandong Province (2024HWYQ-058).
Interpretation limits
Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (321 words)

BackgroundIdiopathic pulmonary fibrosis (IPF) is a fibrosing interstitial pneumonia with restrictive ventilation. Recently, the structural and functional defects of small airways have received attention in the early pathogenesis of IPF. This study aimed to elucidate the characteristics of small airway epithelial dysfunction in patients with IPF and explore novel therapeutic interventions to impede IPF progression by targeting the dysfunctional small airways.MethodsAirway trees spanning the proximal-distal axis were harvested from control lungs and explanted lungs with end-stage IPF undergoing transplant. Qualified basal cells (BCs, p63/Krt5/ITGA6/NGFR) were expanded, and their cellular functions, feasibility, safety and efficacy for transplantation therapy in IPF were validated with experiments in vitro and mouse model. Single-cell RNA-sequencing was employed to elucidate the underlying mechanisms governing the BCs based therapy. Based upon these evidences, three patients with advanced IPF and small airway dysfunction received autologous-BCs transplantation. Post-transplantation assessments included lung function, exercise capacity and high resolution computed tomography (HRCT) scans were analyzed to quantify the clinical benefits conferred by the BCs transplantation.FindingsAn overall landscape of senescent phenotype in airway epithelial cells and airway stem/progenitor cells along the proximal-distal axis of the airway tree in IPF were outlined. In contrast to the cells situated in distal airways, BCs located in small bronchi in IPF displayed a non-senescent phenotype, with comparable proliferative, differentiative capabilities, and similar transcriptomic profiles to normal controls. In a mouse model of pulmonary fibrosis, BCs exhibited promising protective efficacy and safety for transplantation therapy. Autologous BCs transplantation in three advanced IPF patients with small airway dysfunction yielded significant clinical improvements in pulmonary function, particularly evidence in lung volume and small airway function.InterpretationEpithelia of small bronchi in IPF contain functional and expandable basal stem cells, which exert therapeutic benefits via bronchoscopic implantation. Our findings offer a potential for IPF treatment by targeting small airways.FundingNational Natural Science Foundation of China (82430001, 81930001, and 81900059), Shanghai Shenkang Hospital Development Center (SHDC2020CR3063B), Department of Science and Technology of Shandong Province (2024HWYQ-058).

Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 39753035 · DOI · PMC11754162

Key reviews and meta-analyses

The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.

  • Research article Severe and Difficult-to-Treat Asthma in Adults [5]
    Israel E, Reddel HK · N Engl J Med · 2017 · cited 342 times (Europe PMC)
  • Research article Roles of epidermal growth factor receptor activation in epithelial cell repair and mucin production in airway epithelium [6]
    Burgel PR, Nadel JA · Thorax · 2004 · cited 188 times (Europe PMC)
  • Research article Tissue remodelling in chronic bronchial diseases: from the epithelial to mesenchymal phenotype [7]
    Pain M, Bermudez O, Lacoste P, Royer PJ, Botturi K, Tissot A, et al. · Eur Respir Rev · 2014 · cited 177 times (Europe PMC)
  • Research article Respiratory syncytial virus (RSV) and its propensity for causing bronchiolitis [8]
    Pickles RJ, DeVincenzo JP · J Pathol · 2015 · cited 143 times (Europe PMC)
  • Research article Small airway obstruction in COPD: new insights based on micro-CT imaging and MRI imaging [9]
    Hogg JC, McDonough JE, Suzuki M · Chest · 2013 · cited 133 times (Europe PMC)
  • Research article Nicotine exposure and bronchial epithelial cell nicotinic acetylcholine receptor expression in the pathogenesis of lung cancer [10]
    Minna JD · J Clin Invest · 2003 · cited 127 times (Europe PMC)

References

  1. Ter Ellen BM, Dinesh Kumar N, Bouma EM, Troost B, van de Pol DPI, van der Ende-Metselaar HH, et al.. Resveratrol and Pterostilbene Inhibit SARS-CoV-2 Replication in Air-Liquid Interface Cultured Human Primary Bronchial Epithelial Cells. . 2021. PMID 34372541 · DOI · PMC8309965
  2. Yang N, Shang Y. Ferrostatin-1 and 3-Methyladenine Ameliorate Ferroptosis in OVA-Induced Asthma Model and in IL-13-Challenged BEAS-2B Cells. . 2022. PMID 35154576 · DOI · PMC8837457
  3. Yoo JY, Kang SY, Park JS, Cho YJ, Park SY, Yoon HI, et al.. Deep learning for anatomical interpretation of video bronchoscopy images. . 2021. PMID 34887497 · DOI · PMC8660867
  4. Liu Z, Zheng Q, Li Z, Huang M, Zhong C, Yu R, et al.. Epithelial stem cells from human small bronchi offer a potential for therapy of idiopathic pulmonary fibrosis. . 2025. PMID 39753035 · DOI · PMC11754162
  5. Israel E, Reddel HK. Severe and Difficult-to-Treat Asthma in Adults. N Engl J Med. 2017. PMID 28877019 · DOI
  6. Burgel PR, Nadel JA. Roles of epidermal growth factor receptor activation in epithelial cell repair and mucin production in airway epithelium. Thorax. 2004. PMID 15516478 · DOI · PMC1746853
  7. Pain M, Bermudez O, Lacoste P, Royer PJ, Botturi K, Tissot A, et al.. Tissue remodelling in chronic bronchial diseases: from the epithelial to mesenchymal phenotype. Eur Respir Rev. 2014. PMID 24591669 · DOI · PMC9487272
  8. Pickles RJ, DeVincenzo JP. Respiratory syncytial virus (RSV) and its propensity for causing bronchiolitis. J Pathol. 2015. PMID 25302625 · DOI · PMC5638117
  9. Hogg JC, McDonough JE, Suzuki M. Small airway obstruction in COPD: new insights based on micro-CT imaging and MRI imaging. Chest. 2013. PMID 23648907 · DOI · PMC3653349
  10. Minna JD. Nicotine exposure and bronchial epithelial cell nicotinic acetylcholine receptor expression in the pathogenesis of lung cancer. J Clin Invest. 2003. PMID 12511585 · DOI · PMC151841

About this article

Sources
NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
Verification
Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
Review state
automated source verified; no human expert review has been recorded yet.
Version
1, last updated 2026-10-31.

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Related research topics

  • BronchiolesAnatomy and Physiology
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All 542 articles in Anatomy and Physiology →

At a glance

44,230
PubMed records on this heading
7%
published since 2020
2,923
review articles
720
randomized trials
10
verified references below

Counts come from PubMed on 2026-10-31; they show how much has been written, not how strong the evidence is.

Related topics See all →

  • BronchiolesAnatomy and Physiology
  • TracheaAnatomy and Physiology
  • Chronic PainNeuroscience
  • DentitionAnatomy and Physiology
  • BronchoconstrictionAnatomy and Physiology

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