Secondary pulmonary lobule

Dr Jeremy Jones and A.Prof Frank Gaillard et al.

The secondary pulmonary lobule is the functional unit of the lung and is the key to HRCT terminology.

Gross anatomy

Secondary pulmonary lobules measure between 1 and 2.5 cm across. They are polyhedral in shape bounded by fibrous septa (the interlobular septa) which are themselves continuous with the peribronchovascular interstitium (axial connective tissue) and pleura (peripheral connective tissue).

Each lobule contains up to a dozen acini and 30-50 primary pulmonary lobules.

Each secondory pulmonary lobule is supplied by a lobular bronchiole and a pulmonary artery branch. They are drained by pulmonary veins which form in the periphery of the lobule and pass through the interlobular septa. 

Within the secondary lobule, separating adjacent acini is a much less pronounced network of supporting connective tissue which forms the intralobular septa.


There are two sets of lymphatics:

  • central: runs with the arteries in the peribronchovascular interstitium
  • peripheral: in the interlobular septa and drains to the subpleural plexus

See also

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Article information

rID: 8761
System: Chest
Section: Anatomy
Tag: lungs
Synonyms or Alternate Spellings:
  • Secondary pulmonary lobules

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Cases and figures

  • Secondary pulmona...
    Figure 1: secondary pulmonary lobules
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  • Secondary pulmona...
    Figure 2: secondary pulmonary lobules
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  • Figure 3: secondary pulmonary lobules
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  • Lymphangitis carc...
    Case 1: surrounded by thickened interlobular septae
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