Anatomical Study on the Pelvic Diaphragm of Male Balady Dog

The pelvic diaphragm was recently described within the perineal region, the present work categorized the latter into two triangular areas; anal and urogenital. The pelvic diaphragm was a group of fatty and musculofascial structures belonged to each area; a result which wasn’t recorded by the respected available literatures. The study showed the distribution of a thick fatty coat around the superficial and deep aspects of the perineum. The role of the adipose mass was to support the muscles and perineal fasciae.

In general concern, the pelvic diaphragm was integrated in three distinct regions; dorsal, intermediate and ventral. The former, represented the ischiorectal part which lodged in the anal triangle. Nearly achieved findings were mentioned by Budras et al. [12] in dog which described the ischiorectal fossa without the anal triangle. While the recent results revealed that the right and left ischiorectal fossae comprised the anal triangle. On the other hand, the intermediate perineal region connected the dorsal to the ventral one. The latter, included in the urogenital triangle and comprised the urogenital diaphragm, while the intermediate one included the perineal body and muscle. A classification which wasn’t reported in the previous available literatures. Budras et al., [12] in dog had a different classification in which they added three parts of pelvic diaphragm to the coccygeus and levator ani muscle. The authors categorized the parts into anal, perineum proper, and urogenital. The former consisted of external and internal anal muscles and rectococcygeus muscle. The proper division included the perineal body and muscle. While the urogenital one was composed of ischiocavernosus, bulbospongiosus and retractor penis muscle. In this aspect, Sisson and Grossman [13] in domestic animals, Bllenger and Canfield [9] in dog had the opinion that the pelvic diaphragm was consisted of coccygeus and levator ani muscle. The latter authors added the superficial gluteal, internal obturator, external anal sphincter muscle and sacrotuberous ligament.

It was important to note that the ischiorectal part of the pelvic diaphragm of the current study, included the coccygeus muscle group and an anal part (suspensory apparatus of anus). The former, represented the lateral coccygeus muscle and medial coccygeus group (levator ani muscle). A nearly findings were cited by Desai [14] and Miller et al. [15] in dog which reported lateral and medial coccygeus muscle and did not grouped the latter. Evans and delahunta [16] and Budras et al., [12] in dog mentioned coccygeus and levator ani muscle. While Sisson and Grossman [13] in domestic animals had the opinion that there were coccygeus and retractor ani muscle. The lateral coccygeus muscle of balady dog was described as quadrilateral in shape, arose from the ischiatic spine and had cranial, caudal, ventral and dorsal borders. Nearly recorded results were cited by Desai [14] and Miller et al., [15] in dog but they weren’t described its borders and the muscle was attached to the coccygeal vertebrae. However, the present study reported that the muscle was inserted to the lateral aspect of the first three caudal vertebrae. In this aspect, Budras et al., [11] in dog declared that the coccygeus muscle was attached to the first four caudal vertebrae. While Hall et al., [12] in dog cited that it was inserted to the first caudal vertebra.

Concerning the anatomical structures of the medial coccygeus group (levator ani muscle) in the study at hand revealed that the levator ani muscle was grouped into three muscular divisions of thin flat fascicles; Iliococcygeus, pubococcygeus and ischiococcygeus muscle. The former was the cranial and the pubococcygeus was the middle largest while the last was the caudal and smaller one. Nearly findings were cited by Koing and Liebich [17] in domestic mammals which declared that the levator ani muscle represented the iliocaudalis and ischiocaudalis muscle. On the other hand, Hall et al., [11] in dog have the opinion that there were three divisions of the levator ani muscle; pubococcygeus, iliococcygeus and puborectalis. Each part of the levator ani muscle in the balady dog had a distinct area of origin, the iliococcygeus muscle arose from the cranial border of the ilio-pubic junction and the obturator nerve separated it from the pubococcygeus muscle. The present study described the pubococcygeus muscle as the main muscle of the medial coccygeus group with fan shaped fascicles. The muscle originated from dorsal and lateral aspects of the pelvic symphysis and pubis. It was attached dorsally to the anal canal to the 4^th caudal vertebra and related medially to a thick fat bad separated it from the prostate gland. A result which confermed the suggestion of Hedlund [8], Bllenger and Canfield [9], Ferreira and Delgado [6], Ribeiro [10] and Souza et al., [5] which confirmed the relation between the prostatic hyperplasia and the incidence of perineal hernia, where the hypertrophid gland will damaged the fibers of the levator ani muscle. The ischiococcygeus part of the levator ani muscle was attached from the caudo dorsal aspect of the ischial part of pelvic symphysis. In this regard, most of the available literatures, Desai [14] and Miller et al., [15] in dog, Sisson and Grossman [13] in domestic animals and Evans and delahunta [16] and Budras et al., [12] in dog had the opinion that the muscle was a single, not grouped and originated from the medial edge of ilium and dorsal aspect of the pubic symphysis. Sisson and Grossman, added that the muscle originated from the ischiatic spine and sacroischiatic ligament. The recently applied study revealed that all parts of the levator ani muscle were inserted to the 4^th caudal vertebra. A little differences were recorded by Desai [14] and Miller et al., [15] in dog which determined that the muscle was inserted to the 3^rd to 6^th caudal vertebrae. While Budras et al., [12] in dog recorded its insertion to the 4^th to 7^th caudal vertebrae. The name levator ani muscle was referred to the human anatomy, as the normal attitude of the human body allowed the muscle to elevate the anus upward. Regarding that in animals, their normal body posture will changed the name to the retractor ani muscle as considered by Sisson and Grossman [13] in domestic animals. In this aspect, Drake et al., [18] in human declared that the muscle consisted of the ischiococcygeus, pubococcygeus and puborectalis. And the latter surrounded the anal opening and supported it during defecation. That was in agreement with the opinion of Hall et al., [11] in dog. While in contrary to our dissecting observation, where the parts of the medial coccygeus group were inserted to the caudal vertebrae without reinforcement fibers to the sphincter anal muscle. The ischiococcygeus muscle was separated from the external anal phincter by the vertebral head of retractor penis muscle. In this regard, the medial coccygeus muscle group of both sides formed the levator window, which allowed the anal canal to pass through freely with its suspensory apparatus. Where the study used the name medial coccygeus group rather than the levator ani one. Similarly cited results were recorded by Budras et al., [12] in dog which affirmed very few muscle fibers derived from the levator ani muscle to the external anal sphincter and the name levator ani was misleading. A results which were in contrast to that of Desai [14] and Miller et al., [15] in dog, Sisson and Grossman [13] in domestic animals which revealed that the levator ani muscle bended with the external anal sphincter. Ischiococcygeus muscle in the present dissection and that of Koing and Liebich [17] in dog was a homologous to that considered puborectalis by Drake et al., [18] in human and Hall et al., [11] in dog.

Regarding the perineal muscle in the present work, the muscle extended from the perineal body and encircled the lateral sides of the anal canal formed the external anal sphincter. Nearly results were cited by Budras et al., [12] in dog which revealed that the muscle extended from the external anal sphincter to the bulbospongiosus muscle. That was different from the opinion of Hall et al., [11] which mentioned that the anal sphincter muscle originated from the anococcygeal ligament and coursed ventrally on both sides of the external anal opening.

Our dissection revealed that the perineal body was a fibrous mass ventrally located to the anal opening where it gave an attachment for the perineal muscle and fasciae. That was different from that reported by Hall et al., [11] in dog which declared that there were no muscle fibers attached to the perineal body.

The study described the suspensory apparatus of anus and decleared that the retractor penis muscle consisted of four divisions; anal, penile, rectal and vertebral. The former was the broadest, the penile was the longest, the rectal was the smallest and all derived from a common bundle. While the vertebral division descended from the 3^rd caudal vertebra. Nearly similar findings were reported by Budras et al., [12] in dog. In this regard, Evans and delahunta [16] named three parts of the muscle; pars analis, rectalis and penile.

The ventral part of the pelvic diaphragm was recently described, where it comprised the urogenital diaphragm. The latter was composed of dorsal and ventral layers which were considered the deep perineal fascia. Its dorsal layer extended from the pelvic symphysis to the level of ischial arch, where it twirled ventrally to form the ventral layer. A very small deep perineal pouch was formed between them enclosed the ischiourethralis muscle. In case of human, Drake et al., [18] recorded the external urethra muscle was wrapped in the urogenital diaphragm. The ventral layer of the urogenital diaphragm was the perineal membrane which attached cranially to the pubic symphysis. At the ischial arch, it formed the superficial perineal fascia (Colle’s fascia). A result which wasn’t cited in the available respected literatures. The Colle’s fascia covered the superficial perineal pouch which contains the bulbospongiosus and ischiocavernosus muscle. That was similar to findings that reported by Drake et al., [18] in human.