. Principles of modern biology. Biology. Reproduction in Multicellular Animals - 387 FALLOPIAN TUBE URETER. INTESTINE PUBIC SYMPHYSIS URETHRA RECTUM ANUS Fig. 21-9. Genital tract of human female. ovary—in size and shape—resembles a shelled almond (Fig. 21-9), although in older indi- viduals the ovarian surface is roughened and pocketed with numerous scars. These scars re- sult from a repeated rupturing of the ovarian wall during successive ovulations. The human ovaries usually produce only one egg during each 28-day cycle of activity. The egg cell arises from the germinal epi- thelium of the o
. Principles of modern biology. Biology. Reproduction in Multicellular Animals - 387 FALLOPIAN TUBE URETER. INTESTINE PUBIC SYMPHYSIS URETHRA RECTUM ANUS Fig. 21-9. Genital tract of human female. ovary—in size and shape—resembles a shelled almond (Fig. 21-9), although in older indi- viduals the ovarian surface is roughened and pocketed with numerous scars. These scars re- sult from a repeated rupturing of the ovarian wall during successive ovulations. The human ovaries usually produce only one egg during each 28-day cycle of activity. The egg cell arises from the germinal epi- thelium of the ovary (Fig. 21-10). This epi- thelium proliferates periodically, forming a group of cells that is pushed inward from the surface of the ovary and finally pinched off as a separate mass (Fig. 21-10). This mass represents an incipient Graafian follicle, which soon becomes organized into a vesicle, enclosing the maturing egg (Fig. 21-10). The Graafian follicle continues to enlarge until it protrudes slightly from the surface of the ovary. Then, finally, when the egg is ripe, the follicle ruptures, discharging an egg near the mouth of the Fallopian tube. This proc- ess of ovulation occurs periodically in the human female, usually at a fixed time in relation to the menstrual cycle (p. 401). The ovary has also developed two impor- tant endocrine functions, which are associ- ated mainly with the Graafian follicles. As each follicle ripens, it becomes filled with a follicular fluid, which contains the "female sex hormone," estrogen (p. 400). Estrogen has GERMINAL EPITHELIUM D0WNGR0WTH OF EPITHELIUM GRAAFIAN FOLLICLES. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marsland, Douglas, 1899-. New York, Holt, Rinehart and Winston
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