SUPPLEMENTARY:

---

Specialisations of the respiratory epithelium (VHP)

• Cilia can be seen as a darker band on the surface of the tall columnar cells in this section. Details of individual cilia may only be seen at the electron mircroscope level

• Basal cells have dark staining nuclei. They lie close to the basement membrane. They are sometimes known as replacement cells since they undergo mitotic activity to replace ciliated columnar cells

• Goblet cells produce mucus which is secreted onto the surface of the epithelium. They lie between the columnar cells and stain purple in this section. Because the mucus stains intensely it is not usually possible to identify the nuclei of goblet cells.

The lamina propria which lies deep to the epithelium is thin and contains numerous longitudinally arranged elastic fibres which have a pink stippled appearance in TS. These fibres become stretched in inspiration and recoil during expiration. The elastic recoil of the respiratory tissues is very important in expiration. Any loss in the elasticity of the lungs will impair ventilation.