THE SCROTUM AND TESTES
The pendulous scrotum is contained between the cranial parts of the thighs and may reach the level of the hocks. A constricted neck joins it to the trunk, just caudal to the superficial inguinal ring, while its lower part is molded on the testes (Figure 29-27).
A mass of fat (“cod fat”) is commonly found about the cord stump of the castrate; when present in excess, it may dilate the inguinal canal and produce a pseudohernia inguinalis. Although the rudimentary teats often found on the cranial face of the scrotum possess little intrinsic interest, their number and spacing receive attention in dairy bulls because the corresponding characters are likely to be transmitted to their female offspring. The scrotal nerve supply is diffuse; it comes from the first two lumbar, the genitofemoral, and the pudendal nerves.Wool covering the scrotum of the ram may cause infertility by impairing the dissipation of heat.
Each testis is ellipsoidal, large in relation to body size (especially in the smaller ruminants), and hangs vertically in the scrotum, where it may be palpated (Figure 29-28). It carries a large epididymis along the medial or caudomedial border that is turned to face its fellow. The epididymis is firmly attached to this border of the testis; the head extends a considerable distance down the free
| Table 29-1 Age (mo) | Guide to the Aging of Cattle Fetuses | |
| Crown-Rump Length (cm) | External Features | |
| 1 | 1 | Head and limb buds are distinguishable |
| 2 | 6 | Digits are distinguishable |
| 3 | 10 | Scrotal (male) or mammary (female) swelling is distinct |
| 4 | 20 | First hairs appear about the eyes; horn buds are present |
| 5 | 30-40 | Hairs appear about the mouth; testes are within the scrotum |
| 6 | 40-60 | Hair is present on the tail extremity |
| 7 | 50-70 | Hair is present on the proximal parts of the limbs |
| 8 | 60-80 | The haircoat is general but still short and sparse over the belly |
| 9 | 70-90 | The appearance is mature and the body is well haired; the incisors have erupted |
| Full term (278-290 days) | ||
From Evans HE, Sack WO: Prenatal development of domestic and laboratory animals.
Growth curves, external features and selected reference. Anat Histol Embryol 2:11-45, 1973.
| Table 29-2 Age (mo) | Guide to the Aging of Sheep Fetuses | |
| Crown-Rump Length (cm) | External Features | |
| 1 | 2 | Pinna triangular; eyelids forming; tactile hair follicles beginning to appear around eyes; principal forelimb digits prominent |
| 1.5 | 6 | Eyelids fused; external genitalia differentiated; teats present |
| 2 | 11 | Hair begins to cover the body |
| 3 | 24 | Tactile hairs appear on face; testes in upper part of scrotum |
| 4 | 38 | Woolly hair begins to grow; eyes open again |
| Full term (147 | -155 days) | |
From Evans HE, Sack WO: Prenatal development of domestic and laboratory animals. Growth curves, external features and selected reference. Anat Histol Embryol 2:11-45, 1973.
Figure 29-27 Scrotum of bull. Musculature in tunica dartos has been contracted.
border, while the large, conical, and very distinctly palpable tail projects ventrally. The capsule of the testis displays a distinctive winding pattern of vessels and contains the parenchyma under slight pressure; delicate partitions detached from the capsule merge to form a prominent mediastinum (see Figures 5-37 and 5-38).
After emerging from the tail, the deferent duct ascends along the medial border of the epididymis but is separated from this by the mesorchium, which is a relationship that advises a cranial approach in vasectomy operations.
The duct is easily recognized on palpation as a firm, narrow strand. The conical, dorsally tapering spermatic cord is largely composed of the exceptionally convoluted testicular artery embedded in
Figure 29-28 Disposition of the urogenital organs of a bull. 1, Ureter; 2, right testis; 3, epididymis; 4, deferent duct; 5, bladder; 6, vesicular gland; 7, ampulla of deferent duct; 8, body of prostate; 9, bulbourethral gland; 10, sigmoid flexure of penis; 11, glans penis; 12, ischiocavernosus; 13, retractor penis.
the pampiniform plexus (see Figure 5-43). The significance of the arteriovenous anastomoses found here remains obscure: they may be related to the varicoceles occasionally found in the cords of castrated animals (see Figure 5-46). The part of the cord located within the scrotal neck is selected for crushing in the Burdizzo method of castration.
The lymphatic drainage of the testis is to the medial iliac nodes; that of the scrotum is to the superficial inguinal node by the scrotal neck.