Anatomy, Vasculature, and Innervation of the male reproductive tract

Abstract

The male reproductive tract in mammals consists of testes, epididymides, ductus deferentes, accessory sex glands, and penis. The testes differentiate in the fetus from indifferent gonads after expression of the sex-determining region on the Y chromosome (SRY) gene on the short arm of the Y chromosome. Fetal Leydig cells then secrete androgens that induce differentiation of the mesonephric (or Wolffian) duct into the epididymis and ductus deferens and some of the accessory sex glands and of the indifferent external genitalia into a penis and in most eutherians, a scrotum. The size and structural organization of the testes may vary with season, especially in those species that reproduce at a restricted time of year. This is particularly evident in species that occur at high latitudes where testicular development and activity may be regulated photoperiodically or where there is an endogenous circannual rhythm of testis recrudescence, activity, regression, and inactivity. The organs of the male reproductive tract receive a visceral afferent and efferent nerve supply, which is derived from a group of ganglia near the spinal cord, the celiac, aortic, caudal mesenteric, hypogastric, and pelvic ganglia. The scrotum and external cremaster muscle also receive a somatic innervation. The caudal mesenteric and hypogastric ganglia are combined in cats, dogs, rats, and rabbits but are separate in humans, apes, and monkeys. © 2006 Elsevier Inc. All rights reserved.