Porcine Tracheal Goblet Cell Ultrastructure: A Three-Dimensional Reconstruction

In order to study specific anatomical relationships among organelles involved in the movement and secretion of mucin granules by airway epithelium, a three-dimensional replica of a single goblet cell from porcine trachea was constructed by means of transmission electron microscopy of serially prepared ultrathin sections. Many features of the goblet cell that could not be deduced from single planes of section were revealed. The cell is columnar in configuration. The cytoplasm contains not one, but several discrete clusters of mucin granules, each associated with a separate Golgi apparatus. Microtubules and microfilaments often are observed in close association with both mucin granules and coiled filamentous mitochondria, suggesting a role in the intracellular movement of these organelles. These morphological observations are in agreement with previous functional studies of airway mucin secretion, and elucidate further the cellular biology of airway mucosal goblet cells and the secretory process.