Fig. 8.1 Surface features and topographical regions of the pelvis and genitalia: caudal view. The perineal region is shown with the tail raised. It overlies the perineum, which in turn fills and closes the pelvic outlet. It corresponds to the retroperitoneal part of the pelvis and includes muscles and fibrous structures surrounding the anal canal and the termination of the urogenital tracts. The superficial boundary is the skin covering the ischiorectal fossa and extending down to the scrotum below. A horizontal line joining the ischiatic tuberosities separates an anal from a urogenital triangle.

Fig. 8.2 Surface features of the prepuce: ventral view (1). The prepuce is shown completely enclosing the glans penis. The tubular sheath has a normal hairy outer layer continuous with the skin of the abdominal wall and thighs.

Fig. 8.3 Surface features of the prepuce: ventral view (2). The glans penis is protruded through the preputial orifice and the prepuce is rolled back, opening out the preputial cavity.

Fig. 8.4 Surface features and topographical regions of the pelvis and genitalia of the bitch: caudal view. The perineal region of the bitch is shown with the tail raised. Its overall disposition is much like that of the male. The urogenital triangle (also known as the pudendum or pudendal region) incorporates the only visible component of the external genitalia, the vulva positioned below the ischiatic arch. The vestibule connecting vulva with vagina may be up to 5 cm in length.

Fig. 8.5 Surface features of the genitalia of a bitch in oestrus: caudal view. The genitalia of a bitch in heat are shown with the tail raised. The vulva is enlarged and its lips congested and swollen. A blood-tinged discharge from the vulva is also typical of the bitch in heat.

Fig. 8.6 Surface features of the abdomen of a multiparous bitch: ventral view. This multiparous Border Terrier bitch displays two rows of teats. In maiden bitches the teats will be less pronounced. Four pairs are normal for this small breed although 5 pairs would be common in most breeds and very occasionally 6 pairs are present.

Fig. 8.7 Radiograph of the pelvis: lateral view, male dog. The urethra has been highlighted with water-soluble iodine-containing contrast medium. Air has been introduced into the bladder.

Fig. 8.8 Radiograph of the pelvis: lateral view, female dog. Water-soluble iodine-containing contrast medium has been infused into the vestibule, vagina, urethra and bladder. There is also some contrast medium present in the ureters.

Fig. 8.9 Pelvic cavity and sacrotuberous ligament: left dorsolateral view. This is a slightly different view of Fig. 7.20, looking down into the pelvis through the greater ischiatic notch and onto the hip joint. The lumbosacral trunk is clearly exposed in this view leaving the pelvis to be continued as the ischiatic nerve. Caudal to the sacrotuberous ligament the coccygeal muscle and the external anal sphincter muscle form the medial boundary of the ischiorectal fossa (see Fig. 8.66). The internal obturator muscle forming the floor and lateral wall of the fossa leaves the pelvis and its tendon is visible on the gemelli muscles beneath the ischiatic nerve. Immediately cranial to it the hip joint capsule has been exposed and the articularis coxae muscle lies on its surface. The retractor penis muscle and the bulbospongiosus muscle are both exposed on the root of the penis (see Fig. 8.44).

Fig. 8.10 Pelvic bone, hip joint and muscles of the small pelvic association: left lateral view (1). The sartorius, vastus lateralis and rectus femoris muscles have been removed from the cranial surface of the thigh, exposing the medial vastus and iliopsoas muscles with the femoral nerve passing through the latter. Also exposed are the ramifications in the thigh of the superficial circumflex iliac and lateral circumflex femoral vessels. Caudal to the hip joint the ischiatic nerve, the caudal gluteal vessels, the semimembranosus and semitendinosus muscles are all removed. The internal and external obturator muscles, the gemelli and quadratus femoris muscles are visible converging onto the caudal surface of the greater femoral trochanter in the neighborhood of the trochanteric fossa.

Fig. 8.11 Pelvic bone, hip joint and muscles of the small pelvic association: left lateral view (2). Removal of the medial vastus muscle from the front thigh exposes the iliopsoas and pectineus muscles with the femoral vessels running down the thigh cranial to the latter muscle. Although the femoral nerve is largely removed its saphenous branch remains in position in relation to the femoral vessels. Caudal to the hip joint the internal obturator tendon has been removed along with the underlying gemelli muscles. Only the external obturator and quadratus femoris muscles remain of the small pelvic association. Removal of the semimembranosus and semitendinosus completes removal of the ‘hamstring’ muscles and exposes the adductor and gracilis muscles of the inner thigh and the ischiocavernosus muscle of the penile root.

Fig. 8.12 Pelvic bone, external genitalia and inguinal region after removal of the hindlimb: left lateral view. The remains of the hindlimb have been removed by severing the pectineus and iliopsoas muscles (their cut surfaces are clearly exposed); completely removing adductor, gracilis, quadratus femoris and external obturator muscles from their pelvic attachments; and disarticulating the hip joint following severance of its fibrous capsule and internal ligament of the femoral head. The femoral vessels and saphenous nerve are also severed cranial to the pectineus muscle. The bony pelvic wall and floor formed from the pelvic bone are now exposed and extending ventrally from the pelvic symphysis is the midline symphyseal tendon onto which the bulk of the adductor muscles attached. The internal obturator muscle is visible through the obturator foramen and the remnants of the obturator nerve and vessels are exposed. The external genitalia remain completely intact although a small amount of penile skin is removed. The vaginal process extends caudally onto the lateral surface of the penis; superficial inguinal lymph nodes and external pudendal vessels lie in the superficial abdominal fascia cranial to it. Preputial and penile fascia also merge with abdominal and femoral fascia in the fold of the groin and medial side of the thigh.

Fig. 8.13 Inguinal canal (1). External abdominal oblique muscle and superficial inguinal ring: left lateral view. This is a closer view of the inguinal region of a dog and begins a sequence of inguinal canal dissections (see Figs 8.53–8.57 for a ventral sequence in a bitch). Abdominal fascia has been cleared to expose the superficial inguinal ring, and reflection of spermatic fascia has exposed the vaginal process. The femoral vessels are cut back to expose the caudal border of the external oblique muscle.

Fig. 8.14 Inguinal canal (2). Internal abdominal oblique muscle, deep and superficial inguinal rings: left lateral view. The pelvic tendon of the external oblique muscle has been cut close to its merger with the pectineus tendon, and the whole aponeurosis is reflected ventrally, destroying the superficial inguinal ring and the lateral and ventral walls of the inguinal canal. The poorly defined deep inguinal ring is located at the point where the vaginal process crosses the caudal border of the internal abdominal oblique muscle.

Fig. 8.15 Inguinal canal (3). Internal abdominal oblique muscle, spermatic fascia and cremaster muscle: left lateral view. The reflected part of the external oblique has been removed and the line of the cut edge of the tendon is visible on the rectus abdominis muscle where it contributes to the rectus sheath (see Chapter 6). The approximate positions of the inguinal rings, and therefore the extent of the inguinal canal, are shown.

Fig. 8.16 Inguinal canal (4). Vaginal process, pudendoepigastric trunk and genitofemoral nerve: left lateral view. The internal oblique muscle has been dissected away from its origin on the inguinal ligament and is reflected ventrally. The cremaster muscle derived from the internal oblique is also removed from the fascia surrounding the vaginal process.

Fig. 8.17 Inguinal canal (5). Transverse abdominal and rectus abdominis muscles: left lateral view. The reflected part of the internal oblique has been removed and the line of the cut edge of its tendon is visible on the surface of the rectus abdominis parallel to that of the external oblique where both contribute to the rectus sheath. The transverse abdominal muscle also contributes to the superficial layer of the rectus sheath.

Fig. 8.18 Inguinal canal (6). Vaginal process, testicular artery and deferent duct: left lateral view. The transverse abdominal muscle has been cut through on a line with the dorsal edge of the rectus abdominis allowing the rectus to be reflected ventrally away from the abdominal wall, totally destroying what remains of the inguinal canal. Transverse fascia lines the abdomen and here forms the internal layer of the rectus sheath (see Chapter 6).

Fig. 8.19 Pelvic cavity after removal of the pelvic bone: left lateral view. The abdominal wall has been removed and the iliopsoas muscle and external iliac vessels have been cut back into the abdominal roof. The pelvic bone of the left side was removed by sawing through the pelvic symphysis and through the iliac shaft ventral to the sacroiliac joint. The coccygeus muscle was severed from its iliac attachment and the left crus of the penis and left ischiocavernosus muscle were severed at their attachments to the ischiatic arch. The sacrotuberous ligament was cut through at its sacral attachment and removed with the pelvic bone. The internal obturator muscle, attached to the pelvic surface of the pelvic bone, has also been removed. The pelvic cavity is opened from the left side and the levator ani muscle of the pelvic diaphragm is left in position after its origin from the pelvic bone was severed on pelvic bone removal. The preputial cavity has been opened by removal of the left half of the prepuce as far caudally as the preputial fornix on the bulbus glandis. The scrotum has also been opened displaying the testis and epididymis of the left side inside the cavity of the vaginal process.