1. Reproductive System

2. Female Reproductive System
The female gonads are the ovaries. Much like the male gonad, these gonads are responsible for making haploid sex cells and sex hormones.
The ovaries usually produce one egg (or ovum) per month during the process of oogenesis.
Ovulation is the release of the egg from the ovary as it enters an oviduct.

3. The Genital Tract
The oviducts that extend from the ovaries to the uterus have finger-like projections or fimbriae that sweep the egg into an oviduct with the help of cilia.
Fertilization usually takes place in the oviduct; the zygote moves by ciliary movement and oviduct contractions to the uterus, where it implants in the uterine lining (endometrium).

4. The pear-shaped uterus is thick-walled and muscular.
The lower end of the uterus is the cervix that opens into the vagina.
The vagina facilitates sexual intercourse, serves as the birth canal, and acts as an exit for menstrual flow.
A Pap test allows microscopic examination of the cervix tissue for cancer cells.
The endometrium has two layers – a basal layer and an inner, functional layer. In the nonpregnant female, the functional layer of the endometrium varies in thickness according to a monthly reproductive cycle called the uterine cycle.

5. The female reproductive tract
The ovaries release one egg a month; fertilization occurs in the oviduct, and development occurs in the uterus. The vagina is the birth canal as well as the organ of sexual intercourse.
Table 21.2 (page 418) lists the organs of the female reproductive tract along with their functions.

6. External Genitals
The external genital area of the female is the vulva and includes the vaginal opening, urethral opening, clitoris, labia minora, and labia majora.
The vagina may be partially closed by a ring of tissue called the hymen.
The reproductive and urinary systems in females are completely separate.

7. The Ovarian Cycle Female Hormone Levels
An ovary has an outer cortex and an inner medulla; the cortex is where egg cells lie.
A female is born with up to 2 million ovarian follicles (with immature oocytes) that reduce to 300,000–400,000 by puberty, but only 400 follicles mature at the rate of one egg per monthly cycle.
The ovarian cycle is under the control of FSH and LH.

8. Anatomy of ovary and follicle
As a follicle matures, the oocyte enlarges and is surrounded by layers of follicular cells and fluid. Eventually, ovulation occurs, the mature follicle ruptures, and the secondary oocyte is released. A single follicle actually goes through all stages in one place within the ovary.
Primary follicles contain the oocyte and begin producing the sex hormone estrogen.
Secondary follicles contain the secondary oocyte and produce the sex hormones estrogen and some progesterone.
The vesicular (Graafian) follicle develops.
Ovulation: The secondary oocyte is released.
The corpus luteum produces the sex hormones progesterone and some estrogen.
The corpus luteum degenerates.

9. Egg follicles mature, from primary follicles to Graafian follicles.
When the egg is released, the empty follicle becomes the hormone-secreting corpus luteum.
The ovaries produce the female sex hormones estrogen and progesterone.
Estrogen and progesterone exert feedback control over the hypothalamus and the anterior pituitary causing the cycle to begin again.

10. During a follicular phase (day 1-13), FSH from the anterior pituitary stimulates development of an oocyte-containing follicle which secretes estrogen and progesterone.
As the luteal phase comes to an end, menstruation occurs.

11. - As Follicle Develops it puts out increasing levels of Estrogen
- As Follicle Develops it puts out increasing levels of Estrogen. This Estrogen helps prepare the Uterus for possible Implantation
Ovulation occurs on day 14 of a 28-day cycle.

12. During a luteal phase (days 15–28), the corpus luteum develops under the influence of LH and secretes progesterone and estrogen to promote the development of the endometrium.
If there is no fertilization of the egg, therefore no implantation of the developing zygote, then the Corpus Luteum will degenerate. As it degenerates, the levels of Estrogen and Progesterone both drop. This drop in Estrogen and Progesterone is noticed by the Hypothalamus.

13. Hormonal control of ovaries
The hypothalamus produces GnRH (gonadotropin-releasing hormone). GnRH stimulates the anterior pituitary to produce FSH (follicle-stimulating hormone) and LH (luteinizing hormone). FSH stimulates the follicle to produce estrogen, and LH stimulates the corpus luteum to produce progesterone. Estrogen and progesterone maintain the sexual organs (e.g., uterus) and the secondary sex characteristics, and exert feedback control over the hypothalamus and the anterior pituitary.

14. The Uterine Cycle
The female sex hormones, estrogen and progesterone, affect the endometrium, causing the uterus to undergo a cyclical series of events called the uterine cycle.
During menstruation (days 1-5), menses occurs due to the low levels of estrogen and progesterone in the blood.

15. During a proliferative phase (days 6-13), the endometrium thickens.
Ovulation occurs about day 14.
During a secretory phase (days 15-28), the endometrium continues to thicken and becomes vascular.
If pregnancy does not occur the cycle begins again.
Table 21.3 (page 422) summarizes the events of the ovarian and uterine cycles.

16. Female hormone levels
During the follicular phase of the ovarian cycle, FSH released by the anterior pituitary promotes the maturation of a follicle in the ovary. The ovarian follicle produces increasing levels of estrogen, which causes the endometrium to thicken during the proliferative phase of the uterine cycle. After ovulation and during the luteal phase of the ovarian cycle, LH promotes the development of the corpus luteum. This structure produces increasing levels of progesterone, which causes the endometrial lining to become secretory. Menses due to the breakdown of the endometrium begins when progesterone production declines to a low level.

18. Fertilization and Pregnancy
If fertilization occurs, the embryo implants in the endometrium.
The placenta begins to produce human chorionic gonadotropin (HCG), which maintains the corpus luteum and the uterine lining is maintained.
Eventually, the placenta will produce sufficient estrogen and progesterone.
No new ovulations occur during this time.
The placenta originates from both fetal and maternal tissues.

20. Estrogen and Progesterone
At puberty, sex hormones (primarily estrogen) stimulate development of sex organs and maintain the secondary sex characteristics.
Estrogen is primarily responsible for female fat distribution.
Both estrogen and progesterone are needed for breast development.
Females have a wider pelvic girdle than males.