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The skins of vertebrates contain both unicellular glands, which discharge directly to …


Biology Articles » Anatomy & Physiology » Anatomy, Animal » Histological and structural observations on pre-anal glands of the gekkonid lizard, Hemidactylus flaviviridis » Results

Results
- Histological and structural observations on pre-anal glands of the gekkonid lizard, Hemidactylus flaviviridis

Pre-anal glands were found in male but not in female lizards. The ventral femoral region showed the presence of pore-bearing scales in a row on either side of the midline (Fig. 2). In females, the pattern was similar, but the scales were devoid of pre-anal pores (Fig. 1). Most frequently there were five to six pre-anal pores on each side, though the minimum was four and the maximum seven. Each pore was situated near the anterior border of a large scale and all the pores formed a row (Fig. 3). Occasionally, a transluscent paste-like plug of secretion could be seen protruding (Fig. 4). The glands were somewhat flattened and each overlapped by about one third the one immediately lateral to it, working from the midventral line. The first and the last glands in a row were smaller than the others.

In histological section (Fig. 6), each gland was tubulo-acinar, consisting of small closely packed acini separated by connective tissue septa. These septa were continuous with the dermal collagenous tissue. The connective tissue sheath was thickest around the lining of the duct and gradually became thinner towards the blind end of the gland. The epidermal layers of the duct wall in the neck region, where the duct opened to the outside, consisted of a few layers of flattened cells with oval nuclei and an outermost keratinised layer. The inner part of the wall of the duct was lined by stratified epithelium.

The gradual changes in cell structure as reflected by their differential staining properties (depending upon the degree of differentiation of the germinal and differentiating cells) were revealed using haematoxylin and eosin. The non-differentiated peripheral cells of the acini at the blind end of the gland had basophilic cytoplasm whereas the differentiated cells were eosinophilic (Fig. 7). Moreover, the peripheral cells were in a state of proliferation (Fig. 7). The acinar cells in the neck region of the gland revealed a greater degree of differentiation, with their shape changing from polyhedral to oval (Fig. 7) and further becoming somewhat rectangular in a brick-like arrangement (Fig. 8). Increasing eosinophilia appeared to be associated with this structural differentiation. The cells in the transition zone (a zone between the acinar portion and duct of the gland) were fully differentiated. Some cells were intact while others showed various states of disintegration. Their cytoplasm appeared to be granular and more eosinophilic, and the nuclei pyknotic (Fig. 9). Ultimately, such cells appeared to disintegrate and liberate their contents. Increasing nuclear fragmentation occurred as the secretory contents moved towards the pore (Fig. 10). With azan, the germinal cell cytoplasm was stained light blue, suggesting the presence of mucopolysaccharides whereas the differentiating cells in the acini, lumen and transition zone stained red, indicating the presence of keratin, fibrin and lipids. The increasing intensity of red staining suggested the predominance of lipids, keratin and fibrin in the disintegrating cells in the duct region.


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