Hi,
I am currently looking into Trichrome stained section of mouse lung and trying to understand different parts of the lung but it is a bit confusing.
As far as I understood 1,2 are bronchiole, 3-pulmonary artery, 4- not sure, 5-also bronchiole?, 6-artery, 7- bronchiole as well?
Major confusion is between 1 2, 5 and 7 which all look like bronchiole but with different histology, and 4 which I can't clarify.
If anyone can distinguish these please let me know. Thank you so much in advance!
Based on the images you provided, I would agree with your labels.
4 is probably an artery that was sectioned longitudinally rather than cross-sectioned, but I would need a higher magnification image to be sure.
1 and 2 both appear to be bronchioles. Most likely 2 is the start of a branch from 1. The upper label 5 in Lung_2.jpg is also a bronchiole.
What you labeled as 5 at the bottom of Lung_2.jpg, is a respiratory bronchiole. These are distunguished from other bronchioles by the opening into the alveolar space at the top right. Given the the large diameter, that likely also includes part of the bronchiole that it branches off. The U shaped structure in the middle of that image is a another example of a respiratory bronchiole.
7 is a bronchus (likely secondary or tertiary). The cartilage ring around bronchi is a major characteristic that distniguishes them from bronchioles. If you take a look at a higher magnification, you should also be able to see differences in the cells that line the airway (e.g. mucous producing cells present in the bronchi).