20 THE TESTIS AND ITS RELATION TO REPRODUCTION 



and blood vessels) and passes close to the dorsal aspect of the bladder and 

 dorsally to the ureter. It then turns posteriad along the dorsal aspect of the 

 neck of the bladder and the medial region of the ureter, and accompanied 

 by its fellow duct from the other side, it travels toward the prostate gland 

 and the urethra. Just before it enters into the substance of the prostate, it 

 receives the duct of the seminal vesicle. The segment of the vas deferens 

 from the ureter to the seminal vesicle is considerably enlarged and is called 

 the ampulla. After receiving the duct of the seminal vesicle, the vas deferens 

 becomes straightened and highly muscularized — as such it is known as the 

 ejaculatory duct. The latter pierces the prostate gland located at the caudal 

 end of the bladder and enters the prostatic portion of the urethra; from this 

 point the urethra conveys the genital products. 



The auxiliary glands associated with the genital ducts of the human male 

 consist of the seminal vesicles, the prostate gland, Cowper's glands, and the 

 glands of Littre. 



The seminal vesicles are hollow, somewhat tortuous bodies (fig. 2). Each 

 vesicle arises in the embryo as an outpushing (evagination) of the vas deferens. 

 The prostate gland has numerous excretory ducts which empty into the urethra. 

 It represents a modification of the lining tissue of the urethra near the urinary 

 bladder together with surrounding muscle and connective tissues. Cowper's 

 (bulbourethral) glands are small pea-shaped structures placed at the base of 

 the penial organ; their ducts empty into the urethra. The glands of Littre are 

 small, glandular outgrowths along the urethra and are closely associated with it. 



To summarize the matter relative to the structural conditions of the repro- 

 ductive duct in the male of those species which practice internal fertilization: 



( 1 ) A lengthening and twisting of the duct occurs. 



(2) A sperm-storage structure is present, either as a specialized portion 

 of the duct or as a sac-like extension. 



(3) Certain auxiliary glands may be present. These glands are sometimes 

 large and vesicular structures, such as the seminal vesicles of the 

 human duct, or they may be small glands distributed along the wall 

 of the duct, such as the glands of Littre. 



C. Specific Activities of the Various Parts of the Male Reproductive System 



1. Introduction 



a. Three General Functions of the Male Reproductive System 

 The activities of the testes and the accessory parts of the male reproductive 

 system result in the performance of three general functions as follows: 



(1 ) formation of the semen, 



(2) delivery of the semen to the proper place where the sperm may be 

 utilized in the process of fertilization, and 



(3) elaboration of the male sex hormone. 



