Several secretory cells can combine to small groups in the surface epithelium. This creates multicellular intraepithelial glands H, which can be found in the multilayered stratified columnar epithelium of the nasal cavities as well as in the epithelium of the urethra and the conjunctiva of the eye (goblet-cell groups).
This vertical section through the ciliated, multilayered stratified columnar epithelium of the nasal cavity shows goblet cells [2 and a multicellular intraepithelial gland. The cytoplasm of the secretory cells is only faintly stained.
Note also the loosely organized connective tissue of the lamina propria [3.
1 Multicellular interepithelial gland
2 Goblet cells
3 Lamina propria
Stain: alum hematoxylin; magnification: x 400
The secretory cells of active glands accumulate visible supplies of secretory products. This leads to enrichment in secretory materials and their precursors. In the process, the number of conspicuous secretory granules or secretory droplets increases. The acinar cells of the parotid gland show the typical attributes of serous glands. Their many secretory granules are distributed over the entire cell. In electron microscopy, they appear as osmio-E philic spheres. The electron densities of granular membrane and contents are the same. The granular membrane is therefore hardly visible, even at high magnification. The secretory granules are generally released into the lumen H as single granules (exocytosis). However, occasionally the secretory granules in serous gland cells may fuse before they are extruded. This figure shows an acinus of the parotid gland (cf. Figs. 129,379-381,4553 459, 630-632) with osmiophilic secretory granules. On average, the gland cells are cone-shaped. There are secretory canaliculi [2 between gland cells. -2 The nuclei 0 are located in the basal space. O
<L> 1 Acinar lumen
•E 2 Intercellular secretory canaliculi
O 3 Cell nuclei
Q 4 Connective tissue cells
Uj 5 Capillary
Electron microscopy; magnification: x 1800
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