Male Reproductive System

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	The Male Reproductive System consists of: Testes Genital ducts Intratesticular (tubuli recti, rete testis, and ductuli efferentes) Excretory ducts (ductus epididymidis, ductus deferens, and urethra) Accessory glands seminal vesicles prostate gland bulbourethral glands Penis

	Shortly before birth, the testes descend from the abdominal cavity through the inguinal canal into the scrotum. Scrotum: Integument Dartos muscle Tunica vaginalis (peritoneum) Testis: Tunica vaginalis (visceral portion) Tunica albuginea (capsule) Tunica vasculosa Mediastinum Lobules containing seminiferous tubules

	The seminiferous tubules consist of: seminiferous epithelium Sertoli cells spermatogenic cells Lamina propria

	Sertoli cell structure Poorly-defined cytoplasmic outlines. Oval nucleus with a deep indentation and prominent nucleolus Well-developed Golgi complex, abundant sER, little rER, many lipid droplets, moderate number of mitochondria and lysosomes. Sertoli cells are bound to one another by tight junctions. The junctional complex divides the tubule into basal and luminal compartments. The Sertoli-Sertoli junction provides a barrier, the blood-testis barrier, that prevents exposure of the sperm to the immune system. Function of Sertoli cells Support, protect, and provide nutrients for spermatozoa. Establish the blood-testis barrier. Secrete Androgen Binding Protein (ABP). Secrete inhibin. Secrete fluid that facilitates passage of sperm into the intratesticular ducts Control the active release of mature sperm into the lumen. Are actively phagocytic.

	Spermatogenic cells are stacked in 4-8 layers that occupy the space between the basal lamina and the lumen of the seminiferous tubule. These cells divide several times and finally differentiate, producing spermatozoa. This phenomenon from start to finish is called spermatogenesis, and can be divided into three phases: Spermatocytogenesis, during which spermatogonia undergo mitotic division and finally produce primary spermatocytes. Meiosis, during which the primary spermatocyte goes through two successive divisions and produces four spermatids. Spermiogenesis, during which the spermatids differentiate into spermatozoa.



	Spermiogenesis is the process by which spermatids transform into motile mature spermatozoa. This process involves the following phases: Golgi phase. The Golgi apparatus elaborates; a large vesicle, the acrosomal vesicle, forms. Cap phase. The acrosomal vesicle spreads to cover the anterior pole of the elongated nucleus. Acrosomal phase. The anterior pole orients itself toward the base of the seminiferous tubule. The cytoplasm, containing mitochondria, migrates to surround the first part of the flagellum. Maturation phase. Excess cytoplasm is phagocytosed by Sertoli cells. Kartagener's syndrome: a type of infertility characterized by immotile spermatozoa due to the lack of dynein.





	Lamina propria of the seminiferous tubule: The connective tissue contains various typical cell types, including myoblasts, mast cells and macrophages. An additional cell type, the Leydig cell, is also present. At puberty, in response to gonadotrophic stimulation, Leydig cells produce the male hormone, testosterone.

	Functions of the testis: Formation of sperm Production of the androgens (testosterone) Under the influence of the hypothalamus, the adenohypophysis secretes FSH, LH, and prolactin. LH and prolactin, by affecting Leydig cells, cause production of testosterone. FSH causes Sertoli cells to produce ABP and inhibin. Inhibin is involved in the feedback loop that regulates FSH.

	Male genital ducts: Intratesticular ducts tubuli recti (straight tubules) rete testis ductuli efferentes Excretory ducts ductus epididymis ductus deferens (vas deferens) urethra

	Intratesticular ducts: Tubuli recti (straight tubules). These are lined only by Sertoli cells. Near their termination, the tubuli recti narrow, and their lining changes to a simple cuboidal epithelium. Rete testis. An anastomotic network of channels lined by simple cuboidal or low columnar epithelium with a single apical cilium and few apical microvilli. Ductuli efferentes. Pseudostratified columnar epithelium composed of nonciliated cuboidal cells alternating with long columnar ciliated cells. This tall and short cells arrangement gives the epithelium a scalloped appearance. A muscular coat first appears at the beginning of the ductuli efferentes.

	Excretory ducts epididymis ductus deferens urethra Epididymis. A single, highly-coiled tube about 4-6 meters in length. It is lined by pseudostratified columnar epithelium of uniform height with stereocilia. Outside the tubules, smooth muscles are arranged in three layers. The epididymis secretes materials needed for further development of the spermatozoa.

	Ductus deferens. A muscular tube with a narrow lumen. The epithelium is pseudostratified columnar with some stereocilia. The tunica musculare are arranged in three layers. Before it enters the prostate, the ductus deferens dilates to form the ampulla. The epithelium of the ampulla is highly folded (without stereocilia). At the end of the ampulla, the seminal vesicles join the duct and the ductus deferens enters the prostate, opening into the prostatic urethra. The segment entering the prostate is called the ejaculatory duct.

	Urethra: Prostatic urethra Membranous urethra Penile urethra

	Accessory genital glands: Seminal vesicles Prostate gland Bulbourethral glands Seminal vesicles. A pair of highly folded regions of mucosa lined with pseudostratified columnar epithelium, with a discontinuous layer of rounded basal cells and a layer of taller superficial cuboidal or columnar cells. The lamina propria is surrounded by a thin layer of smooth muscle. The secretion of the seminal vesicles contains fructose, citrate, inositol, prostaglandins and several proteins.

	Prostate gland. 30-50 tubuloalveolar glands arranged in three layers around the urethra, a mucosal layer, a submucosal layer (the epithelium of both layers is pseudostratified) and the most peripheral layer containing the main prostatic glands (the epithelium is simple columnar). These glands secrete enzymes, particularly acid phosphatase; measurement of blood levels of this protein are done to check for metastasis in patients with prostatic cancer. Small spherical bodies of glycoprotein called prostatic concretions (corpora amylacea) are observed in the prostate.

	Bulbourethral glands. These paired glands are located on both sides of the membranous urethra; they empty into the proximal part of the spongy urethra. They are compound tubuloalveolar glands lined with simple columnar epithelium.

	The penis is composed of three erectile tissues. Two corpora cavernosa located dorsally, and a corpus spongiosum located midventrally. A dense fibroelastic layer, the tunica albuginea, binds the three together and forms a capsule around each one. Erectile tissue is composed of irregular spaces lined with endothelial cells and whose walls are made of dense collagenenous connective tissue surrounded by smooth muscle. Arteries of erectile tissue have a spiral appearance and are called helicine arteries. Under sexual stimulation, the smooth muscle of the arteries relaxes and blood flows into the cavernous spaces, filling them and producing an erection. Semen: 250-300x106 sperm/ejaculate in a volume of 3ml, consisting of products from the testis, prostate, seminal vesicle, and bulbourethral gland.

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