Lung Under the Microscope (bottom section)
Lung (bottom section), Homo sapiens
This is a frozen section of human lung tissue stained with H&E. It shows the tiny air sacs (alveoli) where oxygen passes into the blood, and it also shows the tears and folds that often happen when soft, airy tissue is frozen and cut.
Frozen section of lung, taken as the bottom face of the frozen tissue block. The tissue is sparse and fragmented, a delicate lattice of thin alveolar septa with widely open airspaces stretched between torn strands. Small foci of vascular congestion stain red toward the mid-left, and denser basophilic strips mark collapsed parenchyma along the fragment edges. The pronounced tearing and discontinuity are classic frozen-section behavior in aerated lung, where ice-supported airspaces shear during cutting — instructive to compare against the better-preserved companion sections in this series.
What to look for
- Alveoli: Many small, open, empty-looking spaces that give lung tissue a lacy, honeycomb look.
- Alveolar walls (septa): Very thin pink walls between the air spaces, dotted with purple nuclei.
- Blood vessels: Tubes of various sizes, some filled with bright pink to red blood cells.
- Collapsed areas: Darker, denser patches where the air spaces have closed up, often near the edges.
- Folds and tears: Darker creases and gaps caused by cutting frozen tissue, not by the lung itself.
At each magnification
Low power (about 4x)
A lacy pink network with lots of open white space, plus darker bands and folds.
Medium power (about 10x)
The pattern of alveoli and the blood vessels running between them.
High power (about 40x)
Thin alveolar walls with flattened cells, purple nuclei, and red blood cells in tiny capillaries.
Questions and answers
What does lung tissue look like under a microscope?
Lung tissue looks like lace or a sponge. Most of it is tiny air sacs called alveoli, separated by very thin walls. With H&E stain, the walls are pink with purple nuclei, and blood in the vessels is red.
Why are alveolar walls so thin?
Oxygen and carbon dioxide move between the air and the blood by diffusion, which only works well over very short distances. The thin walls put the blood in tiny capillaries very close to the air.
What is a frozen section?
A frozen section is made by freezing tissue and slicing it right away instead of embedding it in wax. It is fast, but soft or airy tissue like lung often tears or folds, so some of the gaps and creases on this slide come from the cutting process.
Based upon data generated by the TCGA Research Network (https://www.cancer.gov/tcga) and made available through the NCI Genomic Data Commons (GDC). See credits.
- Category
- Histology and Tissue
- Scan magnification
- 20x
- Stain
- H&E
- Tags
- normal lung tissue, alveoli, alveolar septa, pneumocytes, vascular congestion, atelectasis
Viewing this slide in class
This is a scan of a real prepared slide, not a simulation or a drawing. On StudyScope you can pan from the whole slide down to individual structures, always in focus, and measure them in real micrometers with the calibrated ruler. Present it live and every student screen follows your view and annotations. Students join with a room code on Chromebooks, iPads, or any browser, with no accounts.
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