16 



SPERM, OVA, AND PREGNANCY 



HEAD ISTHMUS TAIL 



Fig. 13.2. Diagrammatic representation of rat epididymis, (a) Scaled diagram of efferent 

 and epididymal ducts in longitudinal section ; luminal diameter scaling one-half that of epi- 

 thelial height, (b) Cross-sections of ducts; epithelial height and luminal diameter drawn to 

 the same scale; sperm arrangement indicated, (c) Relative sperm density, id) General repre- 

 sentation of epithelium, (e) Specific types of cells: a, ciliated cells; b, apical cells; c, basal 

 cells; d, halo cells: e, clear cells. (After B. L. Reid and K. W. Cleland, Australian J. Zool., 

 5,223-246,1957.) 



Seasonal changes in the epididymis have 

 been demonstrated by Wislocki (1949) and 

 others and can be interpreted as represent- 

 ing periodic fluctuations in androgen output. 



D. THE EPIDmVMIS IN RELATION TO 

 SPERM PHYSIOLOGY 



Until more adequate and precise informa- 

 tion is forthcoming concerning the physi- 

 ology of the epididymis, its relation to the 

 changes undergone by the spermatozoa 

 within the tract can only be surmised. Little 

 enough, indeed, is known about the chemical 

 composition of the fluids surrounding the 

 sperm in the rete and efferent ducts, and 

 virtually nothing is known concerning the 

 contributions made by the epididymis as a 

 whole to sperm welfare. Fluid is most likely 

 resorbed from the proximal and intermedi- 

 ate portions of the duct, and some secretion 

 may be contributed in exchange (Mac- 

 millan and Harrison, 1953; Macmillan, 

 1953). The nature of this secretion is ob- 



scure. No mechanism has been suggested to 

 account for the significant quantity of 

 glycerylphosphorylcholine present in the 

 epididymis and epididymal fluid of various 

 mammals (boar, bull, rats, and guinea pigs) , 

 although the concentration of this compo- 

 nent is known to be androgen-dependent 

 (Dawson, Mann and White, 1957; Dawson 

 and Rowlands, 1959), and is presumably se- 

 creted in the proximal portion of the duct. 

 It is unlikely that glycerylphosphorylcho- 

 line or its degradation products serve the 

 sperm in a metabolic capacity, but its pres- 

 ence suggests a possible function in the fur- 

 ther maturation of the gametes (Dawson 

 and Rowlands, 1959). No metabolic sub- 

 strates, e.g., glucose or fructose, have been 

 detected in the fluids of the epididymis. A 

 PAS-positive glyco]iroteinaceous secretory 

 product has been demonstrated in the lumen 

 of the rat epididymis (Maneely, 1958), but 

 its function and relation to sperm transport 

 and survival are obscure. The most com- 



