What Are Goblet Cells?
Goblet cells are glandular epithelial cells – found predominantly in the lining of the digestive and respiratory tracts – whose sole purpose is the secretion of mucus. Mucus is a sticky, viscous substance composed of mucins, enzymes, and electrolytes suspended in water. It coats the epithelium of vulnerable structures to protect them from chemical or mechanical damage, and to trap invading pathogens.
When viewed on slides, goblet cells are usually seen to be goblet-shaped, hence the moniker. They appear narrow at the base, where the nucleus and other organelles are found, and enlarged at the apical portion where the mucus-secreting granules are located. The characteristic shape is actually a result of the expansion of mucus-filled granules during the fixation process, and when care is taken in slide preparation the cells typically appear as simple columnar cells.
Secretion of mucus is usually stimulated by an external irritation, such as digestive acids in the intestine or smoke in the respiratory tract. The mechanism of secretion is primarily merocrine secretion, in which highly concentrated mucus-filled vesicles accumulate within the cytoplasm along the cellular membrane. Upon secretion, the Golgi membrane of the vesicle fuses with the cellular membrane, and the mucus is released into the lumen with no loss of cytoplasm. Immediately upon release into the lumen, the concentrated mucin gel reacts with fluids within the lumen to rapidly change phase and expand up to 500 times its original volume in approximately 0.02 seconds.
Mucus secretion can also be stimulated by the presence of disease. The common cold and influenza virus typically are both characterized by an increase in systemic mucus production. Chronic diseases, such as chronic obstructive pulmonary disease (COPD) or cystic fibrosis, can involve not only increased mucus production but also elevated numbers of goblet cells themselves within the epithelial tissues of the pulmonary tree.
Goblet cells in the esophagus can be an indication of intestinal metaplasia, a phenomenon in which the lining of the esophagus is gradually replaced by tissue similar to that found in the intestine. Upon biopsy, patients with intestinal metaplasia may be diagnosed with Barret's esophagus, a usually benign condition associated with long-term irritation of the esophageal lining. Barrett's esophagus is most often diagnosed in men over 50 years old who have a history of gastroesophageal reflux disease (GERD). It also can be associated with a slightly increased risk of developing a kind of cancer called esophageal adenocarcinoma.
Written by Jessica Gore
