FUNCTION OF THE OVARIES

The Graafian Follicles. Each primitive or primordial ovum is imbedded in a little vesicle or follicle, which is generally known as Graafian follicle, and there are as many Graafian follicles as there are ova. (The Graafian follicles were first described about 250 years ago—in 1672—by a Delft physician named De Graaf, hence the name.) Until puberty, that is the commencement of menstruation, the Graafian follicles with the oöcytes or primitive [53]ova are in a more or less dormant condition. But with the onset of puberty there commences a period of intense activity in the ovaries.

 This period of activity is repeated regularly once a month, and it constitutes the process of ovulation and menstruation. The two processes are closely though not causally connected. Ovulation consists in the monthly maturation and extrusion of a ripe ovum; menstruation, which will be further discussed in a separate chapter, consists in the monthly discharge of blood, mixed with mucus from the inside lining of the uterus. Every twenty-eight days, from the time of puberty to the time of the menopause, a Graafian follicle bursts and an ovum is extruded from the ovary. Before the follicle bursts, it swells and enlarges and reaches the surface of the ovary; the whole follicle is congested with blood, but at one point near the surface of the ovary it is pale and thin, and here the rupture takes place.


Corpora Lutea. After the Graafian follicle has burst and the ovum has been pushed out, the cavity that is left does not remain empty and functionless; there is a further process going on there; there is a growth of cells, of a yellowish color, and the follicle becomes filled with a yellowish body, which on account of its color is called the corpus luteum (plural—corpora lutea; luteum in Latin—yellow, corpus—body). This corpus luteum grows in size until it sometimes occupies as much as one-third of the ovary. But there is considerable difference between the corpora lutea of non-pregnant and pregnant women.

 Up to the end of about a month the corpora lutea are the same, but after that the corpus luteum of the non-pregnant woman begins to get smaller, to shrink, so that at the end of two or three months it is reduced to a small scar and later cannot be noticed at all. The corpus luteum of the pregnant woman keeps on increasing until the end of the second month, remains about the same size until the end of the sixth month, and only then begins gradually to diminish. The corpus luteum of the non-pregnant woman, that is, the one following menstruation, is called false corpus luteum; the corpus luteum following pregnancy is called a true corpus luteum.

The corpus luteum acts like a gland and elaborates a secretion which has an influence on the circulation in the uterus and on menstruation. It probably possesses other properties, with which we are not yet quite familiar. The corpora lutea of various animals are now prepared in powder or tablet form and used in medicine in the treatment of certain diseases of women.