Male Reproductive 5 The Duct System

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			System diagram

The Duct System

After production in the testes, spermatozoa pass through a series of ducts in their journey out of the male system.	Click on the sperm to review the path sperm take from the testis out through the urethra
	Tubuli recti, Rete Testis, Efferent ductules The genital ducts are tubular organs in which the lamina epithelialis varies from the stratified epithelium in the testes to a transitional epithelium in the urethra. In the terminal part of the seminiferous tubules, the epithelium contains only Sertoli cells which gradually blends with the squamous, cuboidal or columnar epithelium (species variation) of the tubuli recti and the rete testis. These epithelial cells may actually represent a continuation of the Sertoli cells which line the seminiferous tubules.
Epididymis The ductus epididymis is lined with a pseudostratified stereociliated columnar epithelium. Stereocilia are actually nonmotile, long microvilli which serve to increase the absorptive and/or secretory surface of this epithelium. With its associated connective tissue and muscle, the ductus epididymis coils to form the head, body and tail of the epididymis which then continues into the ductus deferens. Spermatozoa are stored within the epididymis while they undergo maturation to become mature sperm.	Ductus Deferens The ductus epididymis continues as the ductus deferens which is also lined by a pseudostratified columnar epithelium. However, the lamina propria submucosa of the ductus deferens is areolar loose connective tissue, and the tunica muscularis is very thick and contains two layers of smooth muscle. The tunica serosa is present and typical.

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Urethra
The male urethra consists of two portions; the pelvic urethra and the penile urethra (refer to System Diagram for gross anatomy). Both portions are lined with transitional epithelium, both contain erectile tissue, and both contain (species variable) branched tubular mucous glands, the urethral glands. In the pelvic urethra, the three layers of smooth muscle in the tunica muscularis near the bladder are replaced (or joined in some species) by the striated urethral muscle. The tunica adventitia is present and typical.

In the micrograph to the right, note the transitional epithelium lining the urethra. This epithelium changes from transitional in the pelvic and penile urethra to stratified squamous epithelium at or before the opening of the urethra. In the stallion and boar, glands may be present in the lamina propria-tunica submucosa.

The tunica muscularis is smooth muscle, and cavernous (corpus cavernosum urethra) tissue is present in the connective tissue beneath the epithelium. In the penile urethra, the corpus cavernosum penis is also present. .

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