Histological and Ultrastructural Study on the Meibomian Gland of Camel (Camelus dromedarius)

Document Type : Original Article

Authors

Histology and Cytology Department, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt

Abstract

The health and integrity of the ocular surface is dependent mainly on the meibomian glands (MGs). The MGs are lipid producing holocrine glands embedded within the tarsal plate of both the upper and lower eyelids in most animals. It is well known that the camel's eyelids are devoid of MGs.  Our goals of  this study is to reveal the existence of  MGs in the mature male camel and try to describe its structural and ultrastructural features and correlate   the obtained  data with its function.   The present study was conducted on 10 MGs of mature male camels. The MGs were characterized, fixed, processed and 5µm paraffin sections were prepared and stained with different stains. Other MGs of 1mm³ thick were fixed by Glutaraldehyde and processed for transmission electron microscope. Ultrathin sections were cut and stained with uranyl acetate and lead citrate. Macroscopically,it was an extrapalpebral gland and located in the inferior aspect of the eye with fine hairs on the palpebra tertia surface.  Histologically, the MG was simple branched multilobular acinar glands that was surrounded by dense collagenous connective tissue (C.T.)..They were lined with multiple layers lipid-laden foamy meibocytes.Ultrastructurally, four types of acinar cells were observed: basal cells, moderately differentiated, fully-differentiated and degenerated meibocytes.  The nuclei were flat in basal cells, discoid in moderately differentiated meibocytes, partially  indented from one side by meibomian secretory vesicles(SVs) in fully-differentiated meibocytes and irregular outline with obvious indentation then fragmented in degenerated meibocytes.  The moderately differentiated meibocytes were characterized by many electron dense mitochondria, and various forms of smooth endoplasmic reticulum (sER) which appeared as either grid lattice or parallel cisternae.
Conclusion: The mature male camel has MGs. It was an extrapalpebral gland and located in the inferior aspect of the eye.  It was a large sebaecous gland. The structural characteristics of MGs might reflect their important physiological role in the tear film secretion and maintenance of healthy and integral ocular surface.

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