Type II pneumocytes in the lung alveoli are surfactant-producing cells. They also serve as progenitor cells for alveolar repair. They are histologically identified by which feature?
- A Cuboidal cells with lamellar bodies (osmiophilic multilamellar bodies) on electron microscopy and foamy cytoplasm on light microscopy ✓
- B Flattened squamous cells lining >95% of the alveolar surface
- C Alveolar macrophages with phagolysosomes containing carbon particles
- D Tall columnar cells with cilia in the alveolar ducts
Correct answer: A. Cuboidal cells with lamellar bodies (osmiophilic multilamellar bodies) on electron microscopy and foamy cytoplasm on light microscopy
Explanation
Type II pneumocytes (great alveolar cells) are rounded or cuboidal cells that sit in the corners of alveoli. Their hallmark on electron microscopy is lamellar bodies (osmiophilic multilamellar structures), which are the stored form of surfactant (dipalmitoylphosphatidylcholine). On light microscopy they appear as cuboidal cells with foamy cytoplasm. Type I pneumocytes are the flat cells covering >95% of the surface. Type II cells are the regenerative cells after alveolar injury and increase in number in conditions like ARDS and desquamative interstitial pneumonia.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.