ACTIVITIES OF THE OVARY 85 



Then, under the influence of the hiteinizing hormone, LH, the granulosa cells 

 of the follicle and also cells from the theca interna, together with blood capil- 

 laries, proliferate and grow inward into the antral space (figs. 22, 30, 49). 

 Phagocytes remove the blood clot within the antral space if present, during 

 the inward growth of these structures. As the ingression of cells and capil- 

 laries into the follicle continues, the granulosa cells begin to form large, poly- 

 hedral lutein cells, while the epithelioid cells of the theca interna form a 

 mass of smaller cells which resemble the true lutein cells; the latter are formed 

 in the peripheral area of the corpus luteum and are called paralutein cells. 

 The small spindle-shaped cells of the theca interna, together with blood capil- 

 laries, become dispersed between the lutein cells, forming a framework for 

 the latter. 



If the egg is fertilized, the corpus luteum persists and is known as the 

 corpus luteum of pregnancy; if fertilization does not take place, it is called 

 the corpus luteum of ovulation. The latter body soon degenerates. Histologi- 

 cally, both types of corpora are identical when first formed. Eventually the 

 corpus luteum undergoes involution, and its site becomes infiltrated with 

 connective tissue. The latter structure is sometimes referred to as the corpus 

 albicans. 



12. Hormones of the Ovary and Their Activities in Effecting 

 THE Reproductive Condition 



The ovary produces two important hormones which have a profound effect 

 upon the reproductive process. These two hormones are the female sex hor- 

 mone, estrogen, and the gestational hormone, progesterone. 



a. Estrogenic Hormone 



1) Definition and Source of Production. The induction of estrus (see p. 

 93) or conditions simulating this state is a property of a relatively large number 

 of organic compounds. Because of this estrus-inducing power, they are spoken 

 of as estrogenic substances or estrogens. Estrogens are widely distributed in 

 nature. Two of the most potent natural estrogens are estradiol and estrone 

 (theelin). Both have been extracted from the mammalian ovary and are 

 regarded as primary estrogenic hormones. The most powerful estrogen is 

 estradiol, and it is regarded at present as the compound secreted by the ovary. 

 During pregnancy it also is found in the placenta. These structures are not 

 the only sources of estrogens, however, for it is possible to extract them from 

 urine after ovariectomy, and they occur in the urine of males as well as that 

 of females. The urine of the stallion is one of the richest sources of estrogens, 

 and the testis contains a high estrogenic content (Pincus and Thimann, '48, 

 p. 381 ). Estrogens are found also in various plants, such as the potato, pussy 

 willow, etc. 



