Ultrastructural morphology of goblet cells of the conjunctiva of dogs

OBJECTIVE: To describe the morphology of goblet cells of the eyelid conjunctiva in dogs using transmission and scanning electron microscopy. ANIMAL STUDIED: Ten dogs, both male and female of different breeds, with no ocular changes were examined (20 eyes). PROCEDURES: Ten samples of conjunctiva were collected and processed for scanning and transmission electron microscopy (SEM and TEM), while another 10 samples were stained with Schiff's periodic stain (SPA) and alcian blue, pH 2.5, and analyzed using light microscopy. RESULTS: Scanning electron microscopy revealed several points of mucus extrusion in the free apical portion of the goblet cells as well as a wide distribution of lymphoid follicles and macrophages intermingling with the microvilli of palpebral epithelium cells. TEM revealed normal goblet cells that were predominantly oval with wide cytoplasm of different diameters, and large vesicles with heterogeneous granules and free edges, suggesting the release of mucus content onto the conjunctival surface. Cytoplasmic organelles, such as the Golgi apparatus, endoplasmic reticulum, and a high number of mitochondria were also observed. All the samples were positive for SPA and alcian blue staining. CONCLUSION: This is the first study to evaluate the goblet cells of the eyelid conjunctiva in healthy dogs using electron microscopy techniques. These results are useful for comparing the palpebral conjunctiva of dogs without ocular changes to palpebral conjunctiva of dogs and other species with ocular changes.