Right middle lobe !
The right middle lobe is the small middle part of the right lung, lying against the right side of the heart at the front of the chest.
Official name: Middle lobe of right lung
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What it is
The small wedge-shaped lobe of the right lung, between the horizontal and oblique fissures.
What it does
Lies against the heart on the right; pneumonia here blurs the right heart border on X-ray.
Key facts
- Where
- Anterior, between horizontal and oblique fissures, against right heart border; segments lateral, medial
- Blood supply
- Pulmonary artery branches (gas exchange); bronchial arteries (nourish lung tissue)
- Nerve
- Pulmonary plexus: vagus (bronchoconstriction, secretion); upper thoracic sympathetic (bronchodilation)
- Function
- Gas exchange; consolidation blurs right heart border on chest X-ray
Relations
- Above
- Right upper lobe across the horizontal fissure
- Behind
- Right lower lobe across the oblique fissure
- Medial
- Pericardium over the right atrium, with the right phrenic nerve running between the pericardium and the mediastinal pleura
- Below
- Front of the right dome of the diaphragm
How to find it
It fills a triangle on the front of the right chest: above, the horizontal fissure along the 4th costal cartilage; below and behind, the oblique fissure reaching the 6th costal cartilage. Its breath sounds are listened for in front, beside the lower sternum, and in the axilla.
On imaging
Silhouette sign: middle lobe disease blurs the right heart border, while right lower lobe disease blurs the right hemidiaphragm and leaves the heart border sharp. On the lateral view collapse forms a thin band between the fissures; on the frontal view it may be subtle, with the horizontal fissure dropping.
Common problems
- Pneumonia (infection), asthma and COPD (narrowed airways).
- Lung cancer, often linked to smoking.
- Pulmonary embolism: a clot blocks an artery in the lung.
How it is diagnosed
Listening to the chest, chest X-ray, CT, breathing tests (spirometry), blood oxygen.
Treatment
- Depends on the cause: antibiotics, inhalers, oxygen; surgery removes a lobe or segment for some cancers.
Clinical notes
- Middle lobe syndrome was first linked to enlarged tuberculous hilar nodes; tumours and bronchiectasis are other causes
- The middle lobe and the lingula are the usual sites of bronchiectasis in nontuberculous mycobacterial infection in older women (Lady Windermere syndrome)
- The horizontal fissure is often incomplete, which makes a middle lobe lobectomy technically harder
Anatomical variants
- The horizontal fissure is often incomplete or missing, so the middle lobe may be partly fused with the upper lobe
Development
Around week 5 the lung buds split into lobar buds: three on the right and two on the left, which is why the left lung lacks a middle lobe. The middle lobe comes from the middle of the three right buds.
Related conditions
- Nontuberculous mycobacterial infections (MAC, M. abscessus, Buruli ulcer)
- Transient tachypnea of the newborn
- Community-acquired pneumonia
- Bronchiectasis
Test yourself
Think of the answer, then tap the question to see it.
Which chest X-ray sign separates right middle lobe from right lower lobe consolidation?
Silhouette sign: middle lobe disease blurs the right heart border; lower lobe disease blurs the right hemidiaphragm and leaves the heart border sharp.
Where is the right middle lobe auscultated?
On the front of the right chest between the 4th and 6th costal cartilages and in the axilla; it is hardly heard from the back.
What is middle lobe syndrome, and what favours it?
Recurrent or chronic collapse of the right middle lobe, helped by a long narrow bronchus, surrounding lymph nodes and poor collateral air flow across the fissures.
Which infection typically causes bronchiectasis of the middle lobe and lingula in older women?
Nontuberculous mycobacterial infection (Lady Windermere syndrome).
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- lobus medius pulmonis dextri TA2 3289
- Official Spanish (DeCS)
- Lóbulo medio del pulmón derecho DeCS D008168
- English (TA2)
- Middle lobe of right lung
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Thorax, Lungs; 22.7 Embryonic Development of the Respiratory System (OpenStax (Rice University), 2022) · adapted, CC BY 4.0; Anatomy of the Human Body (20th ed.): The Respiratory Apparatus (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain.
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Representative model, for educational purposes only.
