INTRODUCTION
The ruminant anatomy was generally concentrated on the bovine especially ox with limited comparative points to the small ruminants, especially goat. Goat is belonging to the Caprini of the Bovidae family in the sub-order Ruminantia of the order Artiodactyla. The goat is considered an important source of meat, milk, and hair in Egypt. The male goat is a very familiar animal in Egyptian farms. There are about seven to ten goat breeds in Egypt: Zaraibi, Barki (Sahrawi), Wahati, Sharkawi, and Black Sinai [14]. The three major breeds in Egypt are: Ossimi, Rahmani, and Barki, which are characterised by fat-tailed, their fleece is coarse wool and they are small to medium in size [14].
The male genital systems have to be sound to ensure successful breeding. Ram and buck breeding soundness examination is important to assess the ability to impregnate females during the breeding season [6].
The purpose of the present work was to describe the anatomical position and appearance of the accessory sex glands as well as the microscopic structure of these glands, as there is little available published information about the accessory sex gland of the Barki (Sahrawi) bucks. The study of the accessory sex gland in bucks is very important due to its big role in the fertility rate consideration. Additionally, the obtained data were compared with the previous published anatomical data about the accessory sex glands.
MATERIALS AND METHODS
Animals and ethics
The present work was carried out on eight normal healthy Barki bucks weighing 25–30 kg and the aged between 1 and 2 years. The Barki bucks were collected from the goat farms in the Matrouh government and transported to the Anatomical Laboratory at the Anatomy and Embryology Department, Faculty of Veterinary Medicine, Alexandria University, Egypt.
This study followed the rules for the care and use of animals and was approved by the Animal Welfare and Ethics Committees, Faculty of Veterinary Medicine, Alexandria University, Egypt.
Gross morphology
Four Barki bucks were used in the gross morphological descriptions after their sedation with intramuscular injection of the 2% xylazine HCl (0.2 mg/kg of body weight) and atropine (0.04 mg/kg). Then, these bucks were anesthetised by intravenous injection of ketamine (5 mg/kg). The bucks were injected with heparin (1.000 IU) to obtain well bleeding and prevent the coagulation. Then, they were sacrificed by the well bleeding through the common carotid artery for injection of 10% formalin. The specimens were stored for 2 weeks in formalin 10%. The cadavers were injected via a needle in several sites of the body and on the pelvic cavity using the ordinary preservation solution (10% formalin, 2% phenol, and 1% glycerin).
Computed tomography scans
Two bucks were subjected to computed tomography (CT). After physical examination of animals, they were anesthetised by using the combination of ketamine hydrate 0.5–2 mg/kg of body weight and 2% xylazine HCl 1–3 mg/kg of body weight. The bucks’ cadavers were taken freshly to the CT centre immediately and fixed in the sternal recumbence position and then, serially sectioned using the Hitachi CT scanner (CT-W450-10A, Hitachi, Japan) (scanning conditions: 120 KV and 200 MA, the width and level of the window [W/L]: 2000/250) to examine the accessory male sex reproductive glands. The section thickness was 0.5 cm, part interval in the cross-section from the level of the last lumbar to the fourth caudal vertebrae. The CT images photographed were helpful in the identification of the structures situated from the level of the fifth lumbar and the fourth caudal vertebra. To obtain the good resolution images in the bone windows, the CT machine was adapted with 200 Hounsfield units (HU) in the windows width and 1600 HU in the level of the windows. While in the soft tissue, we adapted the apparatus with 30 HU in the width of the window and 290 HU in the level of the windows.
Light microscopy
Two bucks were used for light microscopic examination. The accessory sex glands were removed from the freshly slaughtered male bucks and were put in 10% normal buffer formalin solution and transported to the histological lab for the histological preparation of the slides (cutting and staining) to allow the examination of the slides under the light microscope to know the characteristic points of each gland. Then, the samples were put in 70% alcohol solution. Next, they were rapidly dehydrated through ascending grades of ethyl alcohol series (30, 50, 70, 90, and 100% for two changes) for a half-hour in each. Then, they were cleared by putting in xylene and embedded in paraffin wax. Samples sections of 5 μm were cut by Leica rotatory microtome and mounted on the glass slides. Finally, the paraffin sections were used for ordinary staining by Harris haematoxylin and eosin (H&E) stain. The histological techniques were carried according to Suvarna et al. [38].
The nomenclature used in this study is adapted to Nomina Anatomica Veterinaria [29].
RESULTS
In all examined bucks, there were four accessory sex glands (Glandulae genitales accessoriae): the paired ampulla of the ductus deferens (ampullary gland), the paired vesicular gland (Glandula vesicularis), the prostate (Glandula prostatica), and the paired bulbourethral gland (Glandula bulbourethralis). All accessory sex glands were located along the pelvic urethra and their ducts opened and empty their secretion into the urethra.
Ampullary gland (Glandula ampulla ductus deferentis)
The ampullary gland (Fig. 1A\LA and RA; Fig. 1B/R.dd; Fig. 6A/4) is a glandular enlargement of the terminal part of the ductus deferens. The length of the ampullary gland reaches 3.5 ± 0.4 cm and the width was 0.5 ± 0.12 cm. The ampullary glands were directed ventrocaudally on the dorsal surface of the urinary bladder and attached by the genital fold (Fig. 1A\GF).
The light microscopic examination showed that the gland (Fig. 2) consisted of the tunica mucosa, tunica muscularis, lamina propria and tunica adventitia, and some blood vessels. The glandular part contained branches of tubuloalveolar glands. The secretory alveoli were lined with a pseudo-stratified epithelium composed of cuboidal to columnar cells with some basal cells.
Vesicular gland (Glandula vesicularis)
In all investigated bucks, the paired vesicular gland (Fig. 1A\LV-RV; Fig. 1B/V; Fig. 6A/3) were located on the craniodorsal aspect of the neck of the urinary bladder (Vesica urinaria) and laterally to the ampullary glands. It could be identified by its appearance that looks like a cluster of grapes and it is important to note that the left vesicular gland was enlarged and higher than the right one in the same buck.
The light microscopic examination clarified that the vesicular gland (Fig. 3) is a lobulated tubulo-alveolar gland with wide intralobular space or sinuses for storage of a large number of secretions. The gland contained a secretory unit lined by pseudo-stratified columnar epithelium, and the interlobular ductules were lined by the stratified epithelium, while the interlobular duct was lined by simple cuboidal epithelium with intra-luminal eosinophilic secretion. The lining epithelium of the secretory part consisted of tall columnar cells, apical blebs of granular end pieces, and detached blebs in lamina, small and spherical basal cells.
Prostate gland (Glandula prostatica)
In all examined bucks, the single prostate gland (Fig. 1/P; Fig. 6B/16) was located close to the junction of the vesicular gland at the pelvic region. It was constituted only from the disseminated part (pars disseminate). The pars disseminate surrounded the pelvic urethra which was covered by the urethra masculina.
The light microscopic examination showed that the prostate gland was enclosed by a connective tissue capsule (Fig. 4) that was thin dorsally, thick laterally, and reduced in thickness ventrally. The gland capsule was enveloped by a layer of skeletal muscle (muscle urethralis) that was surrounded by a layer of loose connective tissue trabeculae extending from the capsule and descending into the parenchyma of the gland forming interlobular connective tissue and divided the gland into lobules. The glandular substance consisted of numerous follicles, which opened into the elongated canal. The prostatic acini were lined by simple cuboidal epithelium.
Bulbourethral gland (Glandula bulbourethralis)
In all investigated bucks, the paired bulbourethral gland was similar in size to the walnut and located dorsal to the urethra in both sides of it, cranial to the ischial arch (Fig. 1A\LB-RB; Fig. 1B/BL; Fig. 6C/23). It was closely related to the bulb of the penis and in general, it appeared to be covered mostly by the bulbospongiosus muscle. The right and left bulbourethral glands appeared to be nearly equal in size and their shape similar to each other.
The light microscopic examination showed that the bulbourethral gland was surrounded by a white fibrous capsule and there were interlobular connective tissue septa that divided the gland into lobes and lobules of different sizes (Fig. 5). The gland contained secretory units lined by the tall simple columnar epithelium of mucous type with basely located nuclei and eosinophilic cytoplasm contained granular secretion.
DISCUSSION AND CONCLUSIONS
There are four accessory sex glands in most mammalian species: ampullary, seminal vesicle, prostate, and the bulbourethral glands in the Barki bucks as reported in horse [8, 12], bull [7, 12], spotted paca [5], Gracilinanus microtarsus [10], Arabian oryx [13], Elk (Cervus canadensis) [22], red deer (Cervus elaphus) [36]. While, the presence of three accessory sex glands was reported in canine (prostate, bulbourethral glands and ampullary gland) [12], canine (prostate, seminal vesicle and ampullary gland) [32], in the pampas deer Ozotoceros bezoarticus (prostate, vesicular and the ampullary glands) [34], in the lesser anteater (prostate, seminal vesicle and bulbourethral glands). However, there are two accessory sex glands only, the prostate and vesicular gland, in the capybara [15]. Furthermore, El-Hagri [12] and Budras et al. [7] reported that the accessory sex glands were fully developed only in the bull.
The present investigation reported that the ampullary gland is a glandular enlargement of the terminal part of the ductus deferens, similar result mentioned by some authors [12, 16, 33, 37]. Furthermore, Fransdon et al. [16] added that its size has a species variation among animal species; well-developed in stallion, bull and ram but, it is absent in the boar; however, Bacha and Bacha [4] and El-Hagri [12] mentioned that it is ill well-developed in the boar but absent in the tomcat and also do Nascimento Lima et al. [10] reported the absence of this gland in Gracilinanus microtarsus. The present histological observation of the ampullary was similar with Trautmann et al. [39] and Wrobel [41] that the gland consists of three layers: the tunica mucosa, tunica muscularis and tunica adventitia.
In all investigated bucks, the paired vesicular gland were located on the craniodorsal aspect of the urinary bladder and it could be easily identified by its appearance which looks like a cluster of grapes and also it’s important to note that the left vesicular gland was enlarged and higher than the right one; similar findings were obtained by some authors [3, 12, 19]. The vesicular gland is the largest accessory sex gland in the bull [7, 12] and the spotted paca [5]. However, the vesicular gland was absent in the canines [12], Gracilinanus microtarsus [10] and some rodents [2, 20]. In the current histological study, the vesicular gland was a lobulated alveolar gland containing a secretory unit that lined by pseudo-stratified columnar epithelium, and the interlobular ductules were lined by the stratified epithelium, while the interlobular duct was lined by simple cuboidal epithelium; similar findings were obtained by some authors [3, 19, 27]. While it was lined by simple cuboidal epithelium as reported in the spotted paca [5], it was lined by a simple columnar epithelium as observed in Guinea pig [40], rat [35] and giant rat [21, 23].
Morphologically, the prostate gland may be single as present in our study and by some authors [12, 17–19, 26, 32] or paired as noted by Junqueira et al. [24]. In our work, we found that the single prostate gland has only the pars disseminate that is found in the pelvic urethra and surrounded by the urethral masculina; similar findings were obtained by some authors [12, 17, 18, 26, 32]. Pathak et al. [31] reported that there is an additional part named the corpus prostate present in some gaddi goats; however, this corpus prostate is not present in small ruminants in all published anatomical textbooks [11, 12, 18].
There is some variation in the portions of the prostate gland among animals species; the present study with and some other authors [12, 17, 18, 26, 32] noted the presence of only one portion called disseminate part, while Gofur [19] in the Black Bengal buck mentioned that the single prostate gland has two portions: compact (external) and disseminate (internal) portion. On the other hand, Junqueira et al. [24] in rat noted that the paired prostate gland has a dorsal and ventral part. Also Neuhaus et al. [28] in the Guinea pig noted that the prostate gland has two portions: the large cranial lobe and the smaller caudal lobe. Moreover, Ojasti [30] in the capybara noted that the prostate gland consists of three parts: intermediate, dorsal and lateral lobes.
According to our histological studies, the prostate gland was enclosed by a connective tissue capsule, which was thin dorsally, thick laterally and reduced in thickness ventrally. The capsule was enveloped by a layer of skeletal muscle surrounded by a layer of skeletal muscle, similar to that reported by Gofur [19] and Pathak et al. [31]. In Guinea pig, the prostate is enveloped by a fibrous muscular layer [1] while in the spotted paca [5] this layer consists of smooth muscle fibre, similar to that observed in the prostate gland of the mouse [9, 25]. The present study noted that the prostatic acini were lined by simple cuboidal epithelium while in the spotted paca [5] it is simple columnar epithelium but pseudo-stratified in some regions.
Our study revealed that the paired bulbourethral gland is small in size similar to hazelnut, and lies dorsal to the pelvic urethra and more obvious as the gland surrounded by a white fibrous capsule; similar observations were noted by some authors [3, 7, 16, 19]. In the spotted paca, the bulbourethral gland presented at the terminal part of the rectum and dorsal to the urethra and caudal to the prostate gland [5]. The bulbourethral gland is absent in the canine and present in the feline, as noted by El-Hagri [12] and Bacha and Bacha [4]. The bulbourethral gland is surrounded by striated skeletal muscle, as noted by Borges et al. [5], Gude et al. [21] and Hebel and Stromberg [23]. Our work mentioned that the bulbourethral gland contains secretory units lined by the tall simple columnar epithelium of mucous type. The lining simple columnar epithelium was also noted by Hebel and Stromberg [23]. The bulbourethral gland appears to be covered mostly by the bulbospongiosus muscle and the gland itself is covered by a white fibrous capsule, similar to that noted by Budras et al. [7].