HISTOLOGY 133 



clitoris striated muscle fibers are also present. Loose connective tissue 

 attaches the urethra to the ventral wall of the vagina. 



Male Genital System 



Figure 63 shows the dissected male genital system which includes the 

 testes, a system of excretory ducts, the accessory glands, the urethra and 

 the penis. 



The testis and its excretory ducts. — The testis is a compound tubular 

 gland in which the male sex cells, the spermatozoa, develop. The organ is 

 covered by a fibrous connective tissue capsule, the tunica albuginea, from 

 which, at the hilus, thin septa project into the gland and divide it into 

 lobules. The lobules contain the convoluted seminiferous tubules. Arteries 

 enter at the hilus, form a network on the inner surface of the tunica albu- 

 ginea, penetrate with the septa, form a capillary network among the semi- 

 niferous tubules and collect into veins, the courses of which correspond with 

 the courses of the arteries. 



The tubules are lined by seminiferous epithelium resting on a basement 

 membrane which, in turn, is surrounded by a thin layer of fibrous connective 

 tissue. The interstitial stroma is rich in blood and lymph vessels and con- 

 tains small groups of interstitial cells (of Leydig). The seminiferous epi- 

 thelium is composed of two kinds of cells, the sustentacular Sertoli cells and 

 the spermatogenic cells. 



Under normal conditions the Sertoli cells lie near the basement mem- 

 brane and are spaced at fairly regular intervals. The cells have large, oval, 

 often indented nuclei and contain a compound nucleolus consisting of one 

 central acidophil and two peripheral basophil bodies. When the cell is 

 resting the nucleus is parallel with the wall of the tubule and the cell is 

 polygonal in shape. When it is fulfilling its function of supporting the 

 developing spermatogenic cells, the nucleus is perpendicular to the wall and 

 the cell is pyramidal in shape. Under abnormal conditions, resulting in the 

 degeneration of the seminiferous cells, the highly resistant Sertoli cells 

 alone line the tubules and their cytoplasm forms a shapeless syncytium. 



The primary spermatogenic cells, the spermatogonia, initiate spermato- 

 genesis by repeated cell division. As the spermato- and spermiogenesis of 

 the mouse do not differ in essentials from other mammals, for a detailed 

 description the reader is referred to Maximow and Bloom's Textbook of 

 Histology (73). Certain phases of spermatogenesis of the mouse are dis- 

 cussed by Cutright (21), Cox (19) Regaud (82) and Yocum (97). 



