SUPPLEMENTARY:

---

Goblet cells and cilia (VHP)

Mucus-secreting goblet cells are scattered throughout the respiratory epithelium, this very high power section shows only one goblet cell. It is not possible to identify the nucleus of the cell which lies close to the basement membrane, however the mucus contained within the cell stains very darkly. Goblet cells are common in the main and lobar bronchi. They become less common and then are absent from the terminal bronchioles. Mucus is secreted by both goblet cells and submucosal glands. Look at the slide in this tutorial which shows the increased number of goblet cells occuring in some respiratory diseases.

The superficial layer of mucus:

• traps inhaled particles such as dust and bacteria
• dilutes irritants and absorbs gases such as SO₂
• moistens inhaled air (saturation with water vapour is necessary for optimal gaseous exchange).

Ciliated columnar cells are the most abundant cell type of the upper respiratory tract.

• they have a basal nucleus and numerous apical mitochondria
  
• cilia are highly specialised extensions of the cytoskeleton which are motile
  
• the luminal surface of each cell bears between 200 and 300 cilia about 6-7m in length. They beat at a rate of 1300 beats per minute in a constant direction i.e. upwards towards the larger ducts and eventually to the larynx