4 i4 HUMAN PHYSIOLOGY 



In the testis the groups of cells form seminiferous tubules, 

 in which the spermatozoa or male elements are developed. 



Ovary. In the adult the ovaries are oval structures covered 

 by a columnar germinal epithelium. In the stroma are 

 seen Graafian follicles in different stages of development. 

 The central cell, the ovum, enlarges. The nucleus becomes 

 prominent, and is sometimes called the germinal vesicle. 

 The nucleolus is also large, forming the germinal spot. The 

 protoplasm becomes encased in a transparent capsule the 

 zona pellucida. The cells of the zona granulosa multiply, 

 and fluid (the liquor folliculi) appears among them, 

 dividing them into a set attached to the capsule of the 

 follicle and a set surrounding the ovum. When the follicle 

 is ripe it projects on the surface of the ovary, and finally 

 bursts, setting free the ovum into the peritoneal cavity. It 

 passes into the trumpet-shaped fimbriated upper end of the 

 Fallopian tube, through which it reaches the uterus. 



Testis. In the adult this is enclosed in a dense fibrous 

 capsule the tunica albuginea. Posteriorly this is 

 thickened, and forms the corpus Highmori. From it pro- 

 cesses extend and form a supporting framework. In the 

 spaces are situated the seminiferous tubules, which open 

 into irregular spaces in the corpus Highmori the rete testis, 

 from which the efferent ducts (vasa efferentia) pass away to 

 join together to form the vas deferens. 



In the seminiferous tubules the spermatozoa are produced. 

 Some of the lining cells divide into two, forming a sup- 

 porting cell and a spermatogen. The latter divides and 

 subdivides till a group of cells lie on the top of the sup- 

 porting cell. These are the spermatoblasts. In each sper- 

 matoblast the nucleus elongates and passes to the attached 

 extremity, the protoplasm decreases in amount, and a long 

 cilium develops from the free end, and the spermatozoon 

 is thus produced. 



Semen. When the testes have become active, the glands 

 of the prostate increase and produce a fluid which, with the 

 spermatozoa, forms the semen. 



Menstruation. In the case of the female the maturation 

 of the ova is accompanied by changes in the uterus. Every 

 four weeks the superficial layers of the mucous membrane of 



