الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Fifty adult she-camels were used to study histological structure of the external genitalia and to immunolocalize sex steroid hormones receptors, VDR and CaBD9k during the breeding and non-breeding seasons. The vestibular wall consists of tunica mucosa, muscularis and adventitia.The vestibule is lined with keratinized stratifiedsquamous epithelium and small patches of stratified columnar epithelium are seen in cranial part of the vestibule.The vestibular epithelium sends rete pegs to interdigitate with papillary bodies of the propria-submucosa. The vestibular epithelium, keratin and rete pegs show a significant seasonal difference as they are thicker during the breeding season. The propria-submucosaconsists of highly vascularized collagenous tissue with elastic fibers. Vestibular bulbs appear asextensive, widely spread, venous plexuses. The vestibular glands are localized mainly within the lateral wall of the middle part of the vestibule.They are in the form of few acinar and more tubular secretory units. They show higher activity during thebreeding season, moreover, the excretory ducts of the vestibular glands appear smaller in size and with empty lumens during non-breeding season, while they appear larger and with secretions in their lumens during breeding season. Tunica muscularis consists of circular and longitudinal smooth muscle layers that are surrounded the constrictor vestibuli muscleswhich are surrounded externally by loose connective tissue of tunica adventitia. The vulva has cutaneous and mucosal surfaces. The cutaneous (outer) surface is covered by pigmented skin with its appendages except sweat glands, while the mucosal (inner) surface is covered by keratinized stratified squamous epithelium.There are no significant seasonal changes in the average thickness of the vulvar epithelium.The core of the vulvar lipconsists of highly vascularized dense collagenous connective tissue with the presence of elastic fibersand few smooth muscle cells. Deep to the vulvar core, circular and longitudinal smooth muscle layers are present and surrounded by constrictor vulvaemuscles which are considered as continuation of constrictor vestibuli muscles. The clitoris is covered with prepuce which is consisted of a pigmented stratified epithelium. The average thickness of the preputial epithelium shows a significant seasonal difference where it is thicker during the breeding season. The clitoral core structure varies from glans to corpus clitoridis.Glans clitoridis consists of cavernous tissueandnerve bundles, while corpus clitoridiscontains cartilaginous and osseous pieces. Lymphocytic infiltrations are common during both seasons in propria-submucosa of all three regions of the external genitalia, but lymphocytic nodules are common during breeding season only indicating higher immune defense during the breeding season. ERα is expressedin the cells of vestibular wall (epithelium, stroma and smooth muscle), vulvar epithelium (mucosal and cutaneous surfaces) and clitoris (preputial epithelium). PR is expressed in the cells of vestibular wall (epithelium, stroma and smooth muscle) and onlyin mucosal surface of the vulva, but it is not seen in the clitoris, vulvar skin and skin appendages. AR is expressed in the cells of vestibular wall (epithelium, stroma and smooth muscle), onlyin mucosal surface of the vulva and clitoris (prepuce and chondrocytes). Both VDR and CaBP9kwere observed only in the epithelial cells of the external genitalia (vestibule, vulva and clitoris). NeitherVDR nor CaBP9kcould be detected in stromaor smooth muscles of the external genitalia. All of ERα, PR, VDR and CaBP9kshowed higher expression in the she-camel’s external genitalia during the breeding season, but only AR showed higher expression during the non-breeding season.These findings indicate that thehigh estrogen concentrations during the breeding season up-regulate and the low estrogenconcentration down-regulate the expression of ERα, PR, VDR and CaBP9k. This is clearly demonstrating the stimulatory effect of estrogen on their expressions. Whereas the high estrogenconcentrationduring the breeding season down-regulate AR expression demonstrating the inhibitory effect of estrogen on AR expression.