[4]. The pudendal nerve passes through the pelvic cavity medial to the sacrosciatic ligament and divides as it approaches the lesser ischiatic notch of the pelvis into proximal and distal cutaneous branches supplying the skin of the caudal hip and thigh [4, 8]. The pudendal nerve continues through the ischiorectal fossa, terminating in a preputial branch, a scrotal branch, and finally the dorsal nerve of the penis [6]. The pelvic nerve provides parasympathetic innervations from the sacral plexus [1]. The hypogastric nerve contributes sympathetic fibers from the caudal mesenteric plexus to the genital system [1] (Figure 1.14).
Figure 1.14 Nerves of the penis: Sc = sciatic nerve, Pu = pudendal nerve, Pc = proximal cutaneous branch of pudendal nerve Scl = sacrosciatic ligament, Stl = sacrotuberous ligament, R = rectum.
Accessory Glands
The accessory genital glands of the bull include the vesicular gland, ampulla of the ductus deferens, and prostate and bulbourethral glands (Figure 1.15). The bilateral vesicular gland is the largest accessory gland in the bull and contributes the greatest volume to the ejaculate. It is a lobated gland of firm consistency. It lies dorsal to the bladder and lateral to the ureter and ampulla of the ductus deferens [1]. The body of the prostate lies dorsal to the urethra between and caudal to the vesicular glands. The disseminate part of the prostate is concealed in the wall of the urethra and covered by the urethral muscle [1]. The ampulla, vesicular glands, and prostate all empty their contents into the urethra through the colliculus seminalis. The bilateral bulbourethral gland lies on each side of the median plane dorsal to the urethra; it is mostly covered by the bulbospongiosus muscle. Its duct opens into the urethral recess [1] (Figure 1.15). The urethral recess is a blind pouch that exits dorsally into the penile urethra at the level of the ischiatic arch. The presence of this structure makes it difficult to pass a catheter retrograde into the bladder.
Figure 1.15 Secondary sex glands: Am = ampulla, Vs = vesicular glands, P = prostate, Bu = bulbourethral gland, Ub = urinary bladder.
References
1 1 Nickel, R., Schummer, A., Seiferle, E., and Sack, W.O. (eds.) (1973). The Viscera of the Domestic Mammals. Berlin: Springer‐Verlag, xiv, p. 401.
2 2 Johnson, A., Gomes, W., and Vandemark, N. (1970). The Testis. New York;: Academic Press, v, illus. 3.
3 3 McGavin, M. and Zachary, J. (2007). Pathologic Basis of Veterinary Disease, 4e, 1476. St Louis, MO: Mosby Elsevier.
4 4 Schaller, O. and Constantinescu, G. (1992). Illustrated Veterinary Anatomical Nomenclature. Stuttgart: F. Enke Verlag, vi, p. 614.
5 5 Ross, M., Kaye, G., and Pawlina, W. (2003). Histology: A Text and Atlas, 4e, 875. Philadelphia: Lippincott Williams & Wilkins.
6 6 Mullins, K. and Saacke, R. (2003). Illustrated Anatomy of the Bovine Male and Female Reproductive Tracts: From Gross to Microscopic, 79. Columbia, MO: National Association of Animal Breeders.
7 7 Watson, J. (1964). Mechanism of erection and ejaculation in the bull and ram. Nature 204: 95–96.
8 8 Budras, K.‐D. (2003). Bovine Anatomy: An Illustrated Text, 138. Hannover, Germany: Schlütersche.
9 9 Ashdown, R. and Smith, J. (1969). The anatomy of the corpus cavernosum penis of the bull and its relationship to spiral deviation of the penis. J. Anat. 104: 153–160.
10 10 Schummer, A., Wilkens, H., Vollmerhaus, B., and Habermehl, K.‐H. (1981). The Circulatory System, the Skin, and the Cutaneous Organs of the Domestic Mammals, 158. Berlin: Springer‐Verlag.
11 11 Brito, L., Silva, A., Barbosa, R., and Kastelic, J. (2004). Testicular thermoregulation in Bos indicus, crossbred and Bos taurus bulls: relationship with scrotal, testicular vascular cone and testicular morphology, and effects on semen quality and sperm production. Theriogenology 61: 511–528.
12 12 Ashdown, R., Gilanpour, H., David, J., and Gibbs, C. (1979). Impotence in the bull. (2) Occlusion of the longitudinal canals of the corpus cavernosum penis. Vet. Rec. 104: 598–603.
13 13 Beckett, S., Wolfe, D., Bartels, J. et al. (1997). Blood flow to the corpus cavernosum penis in the bull and goat buck during penile quiescence. Theriogenology 48: 1061–1069.
2 Endocrine and Exocrine Function of the Bovine Testes
Peter L. Ryan1 and Federico G. Hoffmann2
1 College of Veterinary Medicine, Mississippi State University, Starkville, MS, USA
2 College of Agriculture and Life Sciences, Mississippi State University, Starkville, MS, USA
Introduction
The normal bovine male reproductive system consists of paired testes retained within a sac or purse‐like structure known as the scrotum, which is formed from the outpouching of skin from the abdomen and consists of complex layers of tissue. The testes are accompanied by a number of supporting structures including spermatic cords, accessory sex glands (prostate, bulbourethral, paired vesicular glands), penis, prepuce, and the male ductal system. The testicular duct system is extensive and comprises the vas efferentia found within the testes, epididymis, vas deferens, and urethra, all of which are located external to the testes. The reader is referred to the chapter on the anatomy of the reproductive system of the bull in this book (Chapter 1). The primary functions of the testes are to produce male gametes (spermatozoa) and the endocrine factors, such as steroid (testosterone) and protein hormones (inhibin, insulin‐like peptide 3), which help regulate the reproductive function of the bull in concert with hormonal secretions from the hypothalamus (gonadotropin‐releasing hormone) and pituitary glands (luteinizing hormone (LH), follicle‐stimulating hormone (FSH)). The testes consist of parenchymal tissue that supports the interstitial tissue and includes the steroid‐producing Leydig cells, vascular and lymphatic system, and seminiferous tubules within which the germinal tissue develops with the support of the nurse cells more commonly known as Sertoli cells. Chapter 5 discusses in detail the endocrine factors responsible for testicular development and initiation of spermatogenesis in the bull, and thus this chapter focuses more on the regulation and function of the adult testes. This chapter will not undertake a treatise of those conditions that disrupt testicular function but rather will focus, as practically as is possible, on what is known of the endocrine and exocrine function of the bovine testes. Much of the endocrine and exocrine function of the testes is similar across mammalian species, and where specific information is absent for the bovine, examples will be given from other domestic species when possible. It has not been possible to cite the many significant contributions to the field of endocrine and exocrine function of the testes. Thus, where and when possible, the reader is referred to selected citations
