الفهرس 
AcknowledgementsOnly 14 pages are availabe for public view
 |  | from | 191 |  |  |
| | | from | 191 | | |
Abstract
The Harderian gland was first appeared at the rabbit foeti of 18 days old of prenatal life. The gland appeared as semipatent duct originated from the conjunctival epithelium of the nictitating membrane.
At 21-25 days rabbit foeti, the duct was elongated, excavated and branched into duct branches.The glandular cells at the duct branches were proliferated and arranged themselves in to glandular acini that don’t have central lumen.
At 29 days old rabbit feoti, the acini became luminated, increased in number and grouped around the small duct to show the formation of the Harderian gland lobule.
At the first day of life, the Harderian gland doubled in size and become surrounded by their connective tissue capsule which sent thin septa into the parenchyma of the gland.
The duct system was clearly observed where we could see small intralobular, interlobular, interlober ducts.
At the 3 days old of postnatal life the white and red lobes were clearly differentiated and the main excretory duct was observed at this age.
The epithelium lining the acini of the red lobe was tall cuboidal epithelium with large cytoplasmic secretory vacuoles that surrounded that showed PAS reaction. While the epithelium lining of the acini of the white lobe was columnar cells with oval to rounded nuclei and their cytoplasm was filled with small secretory vacuole in the apical portion, but the lower portion was homogenous. A mixed lobe was observed at 2 month old rabbit Harderian gland.
The Harderian gland released its secretions by merocrine mode from the first day of postnatal life until 2 weeks old rabbit. Then the appocrine mode of secretion was appeared at 2 months of age where it was extremely noticed at the acini of the white lobe cells.
At 4-6 months of age the holocrine mode of secretion was demonstrated.
When the rabbit reached puberty, The Harderian gland appeared lobulated heart shape morphologically.It was the largest orbital structure founded in direct contact with the eye ball at the posterior surface and was attached to the nectitating membrane with convex inner surface and concave outer one.
The adult Harderian gland represented an exocrine multilobulartubuloalveolar gland.
It was covered by thick connective tissue capsule which send connective tissue septa divided the glands into lobes and lobules.
The parenchyma of the Harderian gland was consisted of white lobe and red lobe which was somewhat larger, and in some regions there was a third lobe called the mixed lobe.
At the level of the scanning electron microscope, The Harderian gland showed polygonal and polyhedral glandular cells with domed, bulged or flat apical surface and secretory pits that were irregular or rounded in shape and deep or shallow
The vacuolization of the cytoplasm was more distinct in semi-thin sections stained by Toluidine blue stain. The mode of secretion was clearly visible. The interstitial connective tissue around the secretory end-pieces contained a variety of cells, especially in the white lobe, including; lymphocytes, plasma cells, fibroblasts and macrophage.
At the ultrastructural level of the red lobe, these cells showed abundant smooth endoplasmic reticulum and spherical moitochondria. The lipid vacuoles were larger than that of the white lobe and dispersed in the whole cell cytoplasm. They appeared to be membrane bounded while others non membrane bounded. Also, others appeared to be capped. The lipid vacuoles appeared to be fused with each other and directed toward the apical part of the cell to be exocytosed into the lumen. While some of the secretory cells underwent holocrine secretion.
There was no significant difference observed between the male and female Harderian gland except in the activity.The female gland was more active than the male.
Finally, there was no significant difference between the pregnant and non-pregnant female rabbits in the Harderian gland structure at the level of light and electron microscopical studies.