Caliciformi

Caliciformi, also known as goblet cells, are specialized unicellular glandular cells embedded in the epithelium of mucosal surfaces. They occur throughout the respiratory and gastrointestinal tracts, including the nasal cavity, trachea, bronchi, and the small and large intestine. They are particularly numerous in the colon and in airway mucosa, where they contribute to the protective mucus layer that covers mucosal surfaces.

Morphology: Goblet cells have a flask-like shape with a basal nucleus and an apical region filled with mucin granules. The apical mucin vacuoles give the cell a pale, goblet-like appearance in histological sections. They are non-ciliated and release mucus by exocytosis at the apical surface.

Secretion and function: The mucus consists mainly of gel-forming mucins, such as MUC2 in the intestine and MUC5AC and MUC5B in the airways, hydrated to form a gel. This mucus traps pathogens and particulates and supports mucociliary clearance in the respiratory tract, while providing lubrication and barrier function in the gut.

Regulation and clinical relevance: Goblet cell numbers can increase in response to chronic irritation, inflammation, or infection, a process known as goblet cell hyperplasia. This is common in smoking-related airway disease, asthma, and chronic obstructive pulmonary disease. In the intestine, goblet cells contribute to the mucosal barrier and host defense. Developmentally, they arise from stem cells in the epithelium and differentiate as part of the secretory lineage; turnover is rapid in the intestine and varies in the airways.