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Abstract
The present study was carried out on 32 sexually mature apparently healthy male donkeys (Jacks) ranging from 5 to 9 years to investigate their accessory genital glands morphologically, morphometrically and histochemically during the different seasons of the year, in addition to scanning electron microscopy of the shape of the glandular duct openings. The accessory genital glands of the donkey consisted of the paired ampullae of the deferent duct, the paired seminal vesicles, the prostate, and the paired bulbourethral glands, in addition to the urethral glands.
1- Ampulla of the deferent duct:
- The wall of the ampulla of the deferent duct of the donkey consisted of tunica mucosa, tunica submucosa, tunica muscularis and tunica serosa or adventitia.
- The ampulla of the deferent duct had a folded mucosa lined with principal columnar mostly with blebs and small basal cells. Singly scattered rod-shaped cells were observed between the principal ones.
- The height of the epithelial lining of the ampulla of the deferent duct and its nuclear / cell ratio revealed highly significant seasonal variations. The maximal height (about 20.10 µm + 0.363) and the lowest nuclear / cell ratio (about 0.271 + 0.004) were seen during spring (the active season). During the other seasons (summer, autumn and winter) where the activity decreased gradually, the epithelial height was about 17.98 µm + 0.979, 16.76 µm + 0.404 and 15.92 µm + 0.354 and the nuclear / cell ratio was about 0.276 + 0.009, 0.278 + 0.008 and 0.314 + 0.003, respectively.
- Within the lamina propria-submucosa, the elastic fibers formed a subepithelial network like a girdle surrounding the ampullary lumen. Smooth muscle fibers were also observed within this layer, which arose firstly as thick bundles from the inner circular layer and traversed the whole thickness of the lamina propria-submucosa till the base of the mucosal folds.
- The ampullary glands were of branched tubulo-alveolar variety, which opened directly into the lumen. Their lining epithelium simulated nearly the luminal one. The height of the glandular epithelium and its nuclear / cell ratio showed also highly significant seasonal variations. During spring (active season), the height was about 19.44 µm + 0.209 and the nuclear / cell ratio was about 0.261 + 0.006. During the other seasons (summer, autumn and winter) the epithelial height decreased in contrary to the nuclear / cell ratio. Also the interstitial connective tissue / glandular tissue ratio was at its lowest amount (about 0.066 + 0.006) during spring, this ratio increased gradually from summer, autumn to winter, where it reached about 0.103 + 0.014, 0.147 + 0.006 and 0.175 + 0.017, respectively.
- Glandular principal cells showed often bleb-like apical protrusions especially during spring indicating apocrine mode of secretion.
- The tunica muscularis composed of smooth muscle fibers arranged into inner circular and outer longitudinal layers, with some oblique bundles.
- The tunica serosa covered the reteroperitoneal part, while the rest of the ampulla of the deferent duct was covered by the tunica adventitia.
- The short deferent duct was lined firstly with bi-layered columnar epithelium. It joined the excretory duct of the seminal vesicle forming the common ejaculatory ducts, which lined with stratified columnar epithelium and opened at the Colliculus seminalis. Scanning electron microscopy revealed hexagonal-shaped luminal cell surface with numerous microvilli.
- During spring, strong homogenous PAS positive reactions were detected at the luminal and glandular epithelium as well as at the secretory materials. On the other hand, during winter, most of the secretory end-pieces were negatively reacted.
- Glycogen and lipofuscin pigments could not be detected within the ampulla of the deferent duct of donkey, while the secretory end-pieces with alcian blue were negatively reacted.
- Fine sudanophilic positive granules were observed within the principal and basal cells of both the luminal and glandular epithelium, which increased gradually and reached their maximal amount during the winter.
2- Seminal vesicles:
- The wall of the seminal vesicle of the donkey consisted of tunica mucosa, tunica muscularis and tunica serosa or adventitia. The tunica mucosa possessed numerous primary folds. These foldes carried many secondary branches with numerous tubular invaginations into the underlying connective tissue.
- The luminal epithelium of the seminal vesicles was formed of principal and basal cells, in addition to some clear cells. The height of the lining epithelium revealed highly significant (P<0.01) seasonal variations. During spring, the active season, the epithelial height was about 16.17 µm + 0.370 and the nuclear / cell ratio was about 0.267 + 0.004. These measurements changed gradually during summer, autumn and reached their lowest activity in winter, where the epithelial height was about 12.09 µm + 0.150 and the highest nuclear / cell ratio was about 0.354 + 0.012.
- The glands of the seminal vesicle were of the branched tubular variety, simulating structurally the surface epithelium. Some secretory portions were lined completely with clear cells.
- The glandular epithelium of the seminal vesicle showed also seasonal variations. During the active seasons (spring) the epithelial height was about 16.10 µm + 0.368, the nuclear / cell ratio was about 0.259 + 0.009 and the interstitial connective tissue / glandular tissue ratio was about 0.191 + 0.015. During, the other seasons, these measurements were changed indicating lower glandular activity as in the luminal epithelium.
- The lamina propria was formed of dense connective tissue layer. A network of elastic fibers was observed in relation to the smooth bundles, which extended into the large mucosal folds.
- The tunica muscularis was formed of inner circular and outer longitudinal smooth muscle fibers with some oblique bundles inbetween them.
- The tunica serosa covered the cranial two thirds of the seminal vesicles, while the rest was covered by the tunica adventitia.
- The excretory duct of each seminal vesicle lined by bi-layered columnar or cuboidal epithelium which changed into the stratified type at its joining with the deferent duct, forming the ejaculatory duct.
- During spring, the surface and glandular epithelium as well as the luminal content showed strong PAS positive reaction. Most of the clear cells contained small amount of weakly reacted PAS positive substances except the secretory materials attached to their apical borders, which were strongly reacted. During winter, the epithelium was nearly PAS negative except the secretory substances related to the apical borders of the principal cells.
- The seminal vesicles were free from glycogen and lipofuscin.
- With alcian blue only the luminal content and the secretory materials attached to apical border of the epithelial cells were strongly reacted. Most of the clear cells contained a small amount of moderately reacted alcianophilic granules.
- Few fine sudanophilic granules could be detected within the surface and glandular epithelium of the seminal vesicle of the donkey only during winter.
3- Prostate gland:
- The prostate gland of the donkey consisted of stroma and parenchyma.
- The capsule of the prostate was divided into an outer fiberous and inner fibromuscular layers. from its deep portion, fibromuscular septa extended into the gland dividing it into variable number of lobules.
- The amount of the interstitial connective tissue of the prostate varied among the studied seasons. It showed highly significant (P<0.01) seasonal variations, where the lowest interstitial connective tissue / glandular tissue ratio was about 0.247 + 0.015 during spring (active season). This ratio increased gradually during the rest of the year and reached its highest value during winter (less active season).
- The parenchyma of the prostate was formed of compound tubulo-alveolar glands and duct system. The glandular epithelium of the prostate was consisted of principal with acidophilic granular cytoplasm and basal cells. This epithelium revealed also highly significant (P<0.01) seasonal variations. During the active season (spring) the epithelial height was about 14.67 µm + 0.138 and the nuclear / cell ratio was about 0.224 + 0.013. This activity decreased gradually during the rest of the seasons.
- The duct system of the prostate was organized into tertiary, secondary and primary ducts. The tertiary duct drained into a secondary duct, which drained into a long primary one an opened directly into the urethral lumen. By scanning electron microscope, these openings appeared as elevated dome-shaped papillae.
- During the active season (spring), the epithelial cells lining the majority of the secretory end-pieces revealed strong homogenous PAS positive substances. This reaction decreased in intensity during summer, which became moderate to weak during autumn. While during winter, the majority of the secretory portions were weakly reacted.
- The prostate did not contain glycogen and alcianophilic substance.
- During spring (active season), the glandular and ductal epithelium of the prostate contained few sudanophilic granules, which increased gradually in intensity and amount during the rest of the seasons.
- Few lipofuscin pigments were detected within the glandular and ductal epithelium of the prostate, which increased in amount during summer and autumn and reached their maximum during winter.
4- Bulbourethral glands:
- The bulbourethral glands of the donkey consisted of stroma and parenchyma.
- The capsule was consisted of intermingled circular and longitudinal skeletal muscle fiber layers, in addition to some oblique bundles. This capsule was covered externally with connective tissue layer formed of collagenous and elastic fibers.
- A thick layer of smooth muscle fiber bundles was demonstrated between the muscular capsule and parenchyma only at the attachment of the bulbourethral gland with the urethral wall.
- Fibromuscular trabeculae extended from the deep portion of the muscular capsule into the gland dividing it into variable number of lobules.
- The interstitial connective tissue / glandular tissue ratio revealed highly significant (P<0.01) seasonal variations, where it reached its minimal value (about 0.235 + 0.014) during spring. This value increased gradually during the rest of the seasons, where it reached its maximum (about 0.430 + 0.029) during winter.
- The parenchyma of the bulbourethral glands consisted of glandular portions and duct system. The former was of the compound tubulo-alveolar variety forming variable sized and shaped lobules. The glandular epithelium was formed of principal columnar or cuboidal cells with inconstant basal cells. The epithelium revealed highly significant (P<0.01) seasonal variations. In the active season (spring) the epithelial height measured about 12.96 µm + 0.389 and the nuclear / cell ratio was about 0.280 + 0.005. The epithelial height reached its lowest value (about 10.77µm + 0.268) during winter.
- The duct system simulated nearly that of the prostate. By scanning electron microscope, the bulbourethral gland openings appeared as elevated papillae or rarely as dome-shaped elevation. At higher magnification, their lining cells were hexagonal-shaped with well-developed cell boundaries and numerous ill-developed microvilli.
- The glandular epithelium of the bulbourethral glands of the donkey showed diffuse strong positive PAS reaction. During spring this reaction reached its maximal intensity, which then decreased during summer. This reaction became moderate during autumn, while the lowest PAS reactivity was observed during winter.
- Glycogen and lipofuscin could not be detected within the bulbourethral glands.
- During spring, the glandular epithelial cells and the secretory materials of the bulbourethral glands were moderately reacted to alcian blue. The intensity of this reaction deceased gradually during summer, while during autumn, the alcianophilia became limited to the secretory materials related to apical borders of the principal cells. During winter, the secretory end-pieces were negatively reacted.
- During spring, the glandular and ductal epithelium were negatively reacted with Sudan black stain. While during summer, fine sudanophilic granules were observed. These granules increased gradually in their amount and intensity during autumn and reached their maximum during winter.
5- The pelvic urethra (urethral glands):
- Both regions of the pelvic urethra (prostatic and membranous) of the donkey consisted of tunica mucosa, tunica submucosa, tunica muscularis and tunica adventitia
- The mucosa showed short and few variable-shaped longitudinal folds. The prostatic region was lined with transitional epithelium with patches of stratified columnar and cuboidal one with goblet cells. At the membranous part, it became consisting mostly of a mixture of stratified columnar and cuboidal with numerous goblet cells especially at its ventral aspect. Intra-epithelial cysts and rod-shaped cells were commonly seen.
- The lamina propria-submucosa was formed of highly vascular dense fiberous connective tissue layer containing the cavernous spaces and the urethral glands.
- The urethral glands (glands of Littrè) were mostly branched tubulo-alveolar although simple tubular type was occasionally seen. These glands were lined with principal high cuboidal or pyramidal-shaped cells, with occasionally seen small flat or ovoid basal cells. These glands opened directly into the urethral lumen either directly or by a short duct.
- The glandular epithelium of the urethra revealed highly significant (P<0.01) seasonal variations. During the active season (spring) the epithelial height was about 14.12 µm + 0.314, the nuclear / cell ratio was about 0.285 + 0.007 and the interstitial connective tissue / glandular tissue ratio was about 0.141 + 0.009. During the less active seasons (summer, autumn and winter) the epithelial height decreased gradually, while the nuclear / cell ratio and the interstitial connective tissue / glandular tissue ratio increased gradually to reached their highest values (about 0.321 + 0.008 and 0.289 + 0.028, respectively) during winter.
- The tunica muscularis consisted of thick inner longitudinal and thin middle circular smooth muscle fibers as well as thick outer interwoven skeletal muscle fibers.
- The tunica adventitia covered the entire pelvic urethra, where it consisted of dense connective tissue layer.
- Scanning electron microscopy of the pelvic urethra revealed folded luminal surface with numerous randomly distributed urethral gland openings. They appeared mostly oval- rounded or ovoid in shape. The prostatic urethra was characterized by a convex apical surface of their superficial cells, while at the membranous urethra; the epithelial surface was nearly flat and characterized with somewhat hexagonal-shaped cell apexes. These cells were provided with numerous ill-developed microvilli. Goblet cells were observed within the epithelial lining of the membranous urethra.
- During all studied seasons of the year the cell layers of the transitional epithelium reacted strongly positive for PAS, this reaction became limited to the apical regions of the superficial cells of the stratified columnar and cuboidal epithelium. Within the urethral glands this strong positive PAS reactivity was detected during spring (active season), which decreased in intensity during summer. During autumn and winter this reaction ranged from moderate to weak and from weak to negative, respectively.
- With Best´s carmine, only the transitional epithelium of the prostatic portion reacted strongly positive.
- With alcian blue, only the apical border of the superficial cell layer of the stratified columnar and cuboidal epithelium, the goblet cells and the contents of the intraepithelial cysts were strongly reacted.
- With Sudan black stain, the urethral glands contained fine sudanophilic granules during all studied seasons of the year,
- The pelvic urethra was free from lipofuscin pigments.
from the present study, the accessory genital glands were active all over the year, but this activity was more pronounced during spring which was manifested by increasing epithelial height, decreasing nuclear cell ratio, decreasing interstitial connective tissue / glandular tissue ratio and increasing the cellular secretory activity. This activity decreased gradually during summer and autumn to reached its minimal level during winter.