The male reproductive system includes two testes, which like the ovaries, have a dual function. They produce the male germ cells (spermatozoa) and the male hormones (androgens). The germ cells differentiate to morphologically mature spermatozoa in the seminiferous tubules within the testis. The spermatozoa leave the testis via the rete testis and enter a tubule system including the epididymis and vas deferens, which travels through the abdominal cavity to join with the urethra which enters the penis. Near the bladder, the vas deferens is joined by the seminal vesicle and the prostate gland, forming the ejaculatory duct. The male hormone, testosterone, is produced by the interstitial or Leydig cells found between seminiferous tubules.
The testis is composed of network of highly convoluted tubules, the seminiferous tubules which are lined with spermatogenic cells and supporting cells, the sertoli cells (Seminiferous Tubules 1). The spermatogenic cells differentiate progressively from the basal region of the tubule towards the lumen. Spermatogonia lie in the basal region and undergo mitotic divisions to maintain a stem cell population. Some of the cells produced by these divisions differentiate to primary spermatocytes. The primary spermatocytes are the largest of the maturing germ cells and divide meiotically to give rise to the secondary spermatocytes. These cells are smaller than the primary spermatocytes and are rarely seen in sections, since they divide again rapidly to form the haploid spermatids. Spermatids do not divide, but undergo a morphological transformation (spermiogenesis) to become spermatozoa or sperm. These cells are found in the center of the tubules (Seminiferous Tubules 2). The sertoli cells are tall irregularly shaped cells which abut the basement membrane of the tubule and can be seen between cells throughout the tubule. These cells are easily indentified by their predominate nucleolus (Sertoli Cells). Testosterone is produced by small groups of cells, interstitial or Leydig cells, lying between the seminiferous tubules (Leydig Cells).
The rete testis is a series of anastomosing spaces lined with cuboidal epithelium in the mediastinum through which sperm leave the seminiferous tubules (Rete). The rete testis drain into fifteen to twenty tubules called the ductili efferentes. These tubules penetrate the testis capsule forming the head portion of the epididymis. They are lined with an epithelium composed of high columnar cells with cilia and low non-ciliated columnar cells, and are surrounded by a basement membrane and a thin layer of smooth muscle (Ductili Efferentes). The ductili efferentes runs continuously into the body and tail portions of the convoluted ductus epididymis (Epididymis 1). This tubule is lined with a pseudostratified ciliated columnar epithelium and surrounded by a basement membrane and smooth muscle (Epididymis 2). The epididymis becomes less convoluted and runs continuous with the vas deferens. The vas deferens is a straight tube which travels through the abdominal cavity with blood vessels and nerves, wrapped in connective tissue, forming the spermatic cord. It has a narrow lumen and thick muscular wall, consisting of three layers of smooth muscle (Vas Deferens 1). It is lined with a mucus membrane composed of pseudostratified ciliated columnar epithelium resting on a fibroelastic lamina propria (Vas Deferens 2).
As the vas deferens passes the urinary bladder, a blind, coiled outpocketing in its wall is found. forming an epithelial lined sac, is the seminal vesicle (Seminal Vesicle 1). Its mucus membrane is highly folded and lined with tall columnar cells, surrounded by two layers of smooth muscle and a fibroelastic adventitia (Seminal Vesicle 2). The lamina propria filling the epithelial folds also contains smooth muscle to provide the force for seminal vesicle secretion (Seminal Vesicle 3).
The prostate gland is an aggregation of a large number of individual, irregularly shaped exocrine glands. The epithelium of the secretory alveoli is simple cuboidal to columnar and are surrounded by fibroelastic connective tissue containing numerous smooth muscle fibers (Prostate 1). With increasing age, distinctive swirling prostatic concretions accumulate within secretory alveoli (Prostate 2).
The penis contains three cylinders of erectile tissue; the corpora cavernosa which are two cylinders lying side by side on the dorsal side and corpus spongiosum, a single cylinder on the ventral side which contains the urethra (Penis 1). Each cavernous body is surrounded by connective tissue; all three are surrounded by elastic loose connective tissue and a layer of thin skin. The erectile tissue consists of a framework of irregular trabeculae containing collagen, elastin, and smooth muscle, covered by endothelium. This arrangement produces a number of irregular spaces or blood sinuses, which become engorged with blood to produce the erection (Penis 2).
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