E - Bio @ Horton AP Biology Unit Anatomy and Physiology Notes Female Reproductive System A. Internal Reproductive System 1. Female reproductive system includes: ovaries, oviducts, uterus, and vagina. 2. Ovaries produce an egg each month; are located in the abdominal cavity. 3. Oviducts (Fallopian tubes) extend from ovaries to uterus. a. Oviducts are not attached to ovaries. b. Fingerlike projections called fimbriae sweep over ovaries and waft in egg when it erupts. c. This is normal site for fertilization; embryo is slowly moved by ciliary movement to uterus. 4. Uterus is a hollow, thick-walled muscular organ the size and shape of an inverted pear. a. Embryo completes development by embedding itself in uterine lining, the endometrium. b. A small opening at cervix of uterus leads to vaginal canal. 5. Vagina is a tube at a 45 o angle with the small of the back. a. Mucosal lining lies in folds and can extend. b. It receives the penis during copulation and also serves as birth canal. B. External genitalia of women are known collectively as the vulva. 1. Mons pubis and labia minora and labia majora are to side of vaginal and urethral openings. 2. At juncture of labia minora is the clitoris. a. This is homologous to the penis in males. b. Clitoris has a short shaft of erectile tissue, capped by a pea-shaped glans. c. It contains many sensory receptors that allow it to function as a sexually sensitive organ. 3. Orgasm involves release of neuromuscular tension in muscles of genital area, vagina, and uterus. C. The Ovaries Notes Anatomy and Physiology 1
1. Ovaries alternate in producing one oocyte each month. 2. Ovaries produce an egg (ovum) and female sex hormones, estrogens and progesterone, during ovarian cycle. D. The Ovarian Cycle 1. In longitudinal section, an ovary shows many cellular follicles, each containing an oocyte (egg). 2. A female is born with as many as two million follicles; the number is reduced to 300,000-400,000 by the time of puberty; and only a small number of follicles (about 400) ever mature. 3. As a follicle matures, it develops from a primary follicle to secondary follicle to a Graafian follicle. 4. Öogenesis is occurring; a secondary follicle contains a secondary oocyte pushed to one side of fluid-filled cavity. 5. A Graafian follicle fills with fluid until follicle wall balloons out on surface and bursts, releasing a secondary oocyte. 6. Ovulation is rupture of Graafian follicle with discharge of a secondary oocyte into pelvic cavity. 7. Meanwhile, the follicle develops into corpus luteum; if pregnancy does not occur, corpus luteum begins to degenerate in 10 days. 8. Ovarian cycle is under control of gonadotropic hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). 9. Gonadotropic hormones are not present constantly but are secreted at different rates during cycle. 10. During follicular phase, FSH promotes development of a follicle that secretes estrogen. 11. As estrogen level in blood rises, it exerts feedback control over anterior pituitary secretion of FSH; the follicular phase comes to an end. 12. Estrogen levels in blood rise, causing hypothalamus to secret more GnRH; this causes surge in LH secretion. 13. LH spike triggers ovulation. 14. Luteal phase is second half of ovarian cycle, following ovulation. Notes Anatomy and Physiology 2
a. LH promotes development of corpus luteum, which secretes large amounts of progesterone. b. Progesterone causes endometrium to build up. c. As blood level of progesterone rises, negative feedback to anterior pituitary's secretion of LH causes corpus luteum to degenerate. d. Luteal phase ends and menstruation occurs. E. The Uterine Cycle 1. Estrogens and progesterone affect endometrium of uterus to cause a cycle of events known as the uterine cycle. (Table 50.3) (Fig. 50.11) 2. An average 28-day uterine cycle is divided into four sections. a. During days 1-5, low levels of estrogen and progesterone in the body cause menstruation. 1. Menstruation is periodic shedding of tissue and blood from endometrium; lining disintegrates and blood vessels rupture. 2. Flow of blood and tissues, known as menses, passes out vagina. b. During days 6-13, increased production of estrogens by an ovarian follicle causes endometrium to thicken and become vascular and glandular (proliferative phase). c. Ovulation usually occurs on day 14 of 28-day cycle. d. Days 15-28 see increased production of progesterone by corpus luteum causes endometrium to double in thickness; uterine glands mature, producing thick mucoid secretion (secretory phase). 1. Endometrium is now prepared to receive a developing embryo. Notes Anatomy and Physiology 3
2. If no pregnancy occurs, progesterone and estrogen levels decline and corpus luteum degenerates. 3. With low levels of progesterone, uterine lining also begins to degenerate. 4. During menstruation, anterior pituitary increases FSH production; a new follicle begins to mature. 5. The birth control pill contains varying levels of progestins and estrogen. The high level of these two hormones prevents the release of LH and thus ovulation does not occur. In the final days of the cycle the pill has no hormones and allows normal menstruation to occur. 3. Ovarian cycle controls uterine cycle. F. Events Following Fertilization 1. If fertilization occurs, embryo begins development as it travels down oviduct to uterus. 2. Embryo becomes embedded in endometrium several days following fertilization. 3. Placenta develops from both maternal and embryonic tissues. a. Placenta functions to exchange gases and nutrients between the fetal and maternal circulation. b. There is normally no mixing of blood itself. 4. Initially, placenta produces human chorionic gonadotropin (HCG) which maintains corpus luteum. 5. Corpus luteum is maintained by HCG until placenta produces its own progesterone and estrogens. 6. Progesterone and estrogens have two effects at this stage. a. They shut down the anterior pituitary so that no new follicles mature. b. They maintain lining of uterus so corpus luteum is not needed. 7. There is no menstruation during pregnancy. G. Functions of Estrogen and Progesterone 1. Estrogens maintains secondary sex characteristics of females. 2. There is less body and facial hair; more fat beneath skin provides a more rounded appearance. 3. Pelvic girdle enlarges and pelvic cavity is larger; therefore, women have wider hips. 4. Both estrogen and progesterone are required for breast development. Notes Anatomy and Physiology 4
H. The Female Breast 1. Female breast contains 15-24 lobules, each with a mammary duct. 2. Mammary duct begins at nipple and divides into numerous ducts which end in alveoli (blind sacs). 3. Prolactin hormone is needed for lactation (milk production) to begin. 4. Production of prolactin is suppressed by the feedback inhibition that estrogens and progesterone have on the anterior pituitary during pregnancy. 5. It takes a couple of days after delivery of a baby for milk production to begin. 6. Breasts produce a watery, yellowish white fluid (colostrum) similar to milk but containing more protein, less fat and rich in antibodies providing some immunity to newborn. What you need to know from notes the anatomical components of the female reproductive system the ovarian cycle and ovum production the uterine cycle and hormonal control development following fertilization the role of the placenta in development the role of estrogen and progesterone in development the role of the female breast in milk production Images: Campbell, Neil and Reece, Jane. Biology (6 th ed.) San Francisco: Benjamin Cummings Modified Notes: Mader, Sylvia. Biology (7 th ed) New York: McGraw Hill Publishing Notes Anatomy and Physiology 5