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This section of salivary gland was stained with H&E. It shows the mixture of serous secretory units, mucous secretory units and ducts. The serous cells are stained purple with the basic dye hematoxylin due to their high content of cytoplasmic RNA. This is an example of cytoplasmic basophilia. The mucous cells are unstained, because neither dye stains mucus. The cytoplasm of cells forming the ducts that are found amongst the secretory units is stained red-pink with eosin due to the presence of cytoplasmic proteins. This is referred to as acidophilic or eosinophilic staining. A nucleus in the duct cell is marked by arrow. It is basophilic, due to its containing DNA and RNA.

You should be able to identify:

• Cell nucleus
• The location of the nuclear envelope (marked by a dark basophilic ring around the nucleus due to adsorbed chromatin, containing DNA)
• Nucleolus (a basophilic structure inside of the nucleus, containing both DNA and RNA) (how many per nucleus?)
• Cytoplasmic basophilia - present in secretory cells but not in duct cells
• Cytoplasmic acidophilia - see the duct cells
• Cell outlines
• Mucus - does not stain with hematoxylin or eosin

Stain: Hematoxylin and eosin