Studies on Morphological and HistochemicalSeasonal changes on the lacrimal Apparatus of the One-humpedcamel Camelusdromedarius

Abstract

This study aimed to investigate the seasonal gross anatomy, histolology, histometry and histochemistry of the camel lacrimal apparatus. One hundred and twenty five heads from both sexes of healthy adultdromedary camels were collected from Omdurman and Tambul slaughterhouses. The camel lacrimal gland was located at the dorsolateral part of the eyeball and convex dorsally and concave ventrally. The gland which was light red in colour was lobulated and irregularly triangular in shape with three borders; in some specimens was observed a ventral accessory lobe. There were insignificant seasonal differences in the glandular weight, length, width and thickness (P ˃ 0.05). However, there was a significant difference in Summer between the thickness of the right and left glands (P < 0.05). The excretory duct penetrated the periorbita and opened into the superior conjunctiva. The main lacrimal gland had two excretory ducts and the accessory lobe had its own duct. No punctalacrimalia were found and the two lacrimal ducts started blindly and opened into the lacrimal sac. The nasolacrimal duct extended from the lacrimal sac to its external opening which was located at the ventral part of the opening of the nasal diverticulum and dorsal to the Vomer bone. The lacrimal gland was surrounded by a thick connective tissue capsule which sent connective tissue septa that divided the gland into lobes and lobules. The gland was tubuloalveolar in structure. The alveoli and tubules were lined by simple cuboidal epithelim which was surrounded by myoepithelial cells. The intralobular duct was lined by low simple columnar epithelium. The interstitium was formed of loose connective tissue around the acini, tubules and intralobular ducts. The secretory units and intralobular ducts were also surrounded by a thin layer of reticular fibres. The interlobular duct was lined by simple to stratified columnar epithelium. The excretory duct was lined by stratified columnar epithelium. The interlobular and excretory ducts had many large goblet cells and surrounded by connective tissue containing blood vessels, nerve fibres and adipose tissue. The lacrimal duct and lacrimal sac had an irregular mucosa and were lined by stratified columnar epithelium containing large gobletcells and surrounded by a dense connective tissue containing smooth muscles, irregular blood vessels (venous plexuses) and lymphocytes. The nasolacrimal duct was lined by a stratified columnar epithelium with goblet cells. The goblet cells and mucoserous glands in the vascular connective tissue increased towards the terminal part of the gland. No significant difference was observed in the glandular epithelial height, diameter of secretory unit’s and interstitial tissue thickness between Winter and Summer. The acini were generally Alcian blue (pH-2.5) negative and the reactions in the tubules, intralobular ducts, interlobular ducts and excretory ducts were strongly positive. The reaction intensity increased in the different glandular tissue in Summer season. The glandular acini, tubules, intralobular ducts, interlobular ducts, excretory ducts and connective tissue septa were strongly PAS positive and the reaction was comparatively stronger in Summer. alcian blue/ PAS sequence showed strong PAS reaction in the tubules and intralobular duct, whereas alcian blue was observed in a few epithelial cells. The epithelial cells of the acini were only PAS positive. Strongly positive alcian blue reaction was observed in many goblet cells of the interlobular and excretory ducts; some cells showed mixed alcian blue and PAS reaction. The intensity of these reactions increased in Summer as compared to Winter season.The acidic tubular lacrimal mucinswere mainly carboxylated in Winter and the acidic acinarmucins are mainly sulphated in Summer.Glycogen was absent from the lacrimal gland in Winter and Summer.