In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Reduced size of capillary lumen and occlusion were caused by swollen endothelial cells which had luminal protrusions and swollen microvilli .
### Output Text:
Reduced size of capillary lumen and occlusion were caused by swollen endothelial cells which had <span class="chemical">luminal</span> protrusions and swollen microvilli . 