464 



PHYSIOLOGY OF GONADS 





It:- 









'^l&^h 



■ ■;%.%, 





Fig. 7.7. iiniuaiKi. li.\ pupliy.sectomized rat treated with estrogen (dit'thylstilbe.Ntrol). 

 Many follicles have developed to a size appropriate for antrum formation. The interstitium 

 i.s atrophic but the theca is differentiated. One follicle is obviously atretic. (Courtesy of Dr. 

 J. T. Bnidburv.) 



atresia than those which have entered the 

 growth phase. 



Hisaw (1947) discussed the problem and 

 marshaled a number of facts in support of 

 the idea that atresia is due to a defective 

 differentiation of the theca interna, with a 

 ^resulting deficiency of estrogen which is 

 considered necessary for growth and differ- 

 entiation of the granulosa. Ultimately the 

 ])ituitary is involved because the success 

 which has been achieved in the j^roduction 

 of sui)erovulation reveals that the number 

 of follicles maturing and ovulating is a 

 measure of the amount of gonadotrophic 

 hormone. But it is eciually true that there is 

 an optimal dosage and time beyond which 

 defects appear in the form of cystic follicles 

 and premature luteinization (see review by 

 Hisaw and more recently Zarrow, Caldw(>ll, 

 Hafez and Piiicus, 19581. 



The disintegration of the discus proligerus 

 of the nuiture follicle and the dissolution of 

 the granulosa in an atretic follicle have 

 led several investigators to suggest that the 



stimulus to ovulation and/or atresia is iden- 

 tical (Harman and Kirgis, 1938; Dawson 

 and McCabe, 1951 ; Moricard and Gothie, 

 1953; Williams, 1956). Moricard and Gothic 

 found that intrafollicular injection of HCG 

 or P]\1S caused first polar body formation 

 within 4 liours. Control injections of estro- 

 gen or scrum were ineffective. Dempsey 

 (1939) noted that maturation spindles were 

 present in ne:iily all the oocytes in medium 

 and large follicles which had undergone 

 atresia shortly after ovulation had been in- 

 duced by luteinizing hormone. Inasmuch as 

 the tubal egg ntay give off the second polar 

 body about the time the corona radiata is 

 lost, it is interesting to speculate on the sig- 

 nificance of the fact that the eggs in atretic 

 follicles may also give off polar bodies just 

 as they are denuded of granulosa (Fig. 7.8). 



V. Hormones of the Ovary 



The hoi'mones of the ovary are the estro- 

 gens, pi-ogesterone. androgen, and relaxin. 

 The first three are the o\'ai"ian steroid hor- 



