Chapter 17

Female Reproduction

The Female Reproductive System Produces Eggs and Nurtures the

Embryo and Fetus

• Ovaries: release oocytes and secrete the hormones estrogen and progesterone

• Oviduct (a.k.a., Fallopian Tube)–After ovulation eggs enter oviduct

–Site where fertilization occurs

–Site of ectopic pregnancy

Female Reproductive System

• Uterus: the organ where fertilized egg grows and develops–Layers

• Endometrium: supports fertilized egg, sloughs off during menstrual flow

– Endometriosis: ectopic growth outside uterus

• Myometrium: Thick muscular layer, expands during pregnancy & responsible for labor contractions during childbirth

• Cervix: the narrow opening in the lower part of the uterus that permits sperm to enter the uterus

Female Reproductive System

True / False

• Fertilization normally takes place in the uterus.

True / False

• Implantation of the embryo normally occurs in the oviduct.

The Ovarian Cycle

• Purpose:– Egg production and ovulation

Mature (Graafian) Follicle

The Menstrual Cycle

• The ovarian and uterine cycles are coordinated by hormones– Estrogen, Progesterone – Luteinizing Hormone (LH)– Follicle Stimulating Hormone (FSH)

• Ovarian Cycle: oocytes mature and are released– Follicle develops under the influence of FSH– Follicle produces increasing estrogen– (Graafian) Follicle matures & produces lots of

estrogen– Increasing estrogen causes surge of LH (positive

fdbk) which induces ovulation– Corpus luteum (CL) formed from follicle, large

amounts of progesterone secreted– CL degenerates and progesterone declines

Menstrual Cycle: Ovarian Cycle

Ovarian follicles

A. Are stimulated to develop by FSH

B. Contain a single egg

C. Secrete estrogen

D. Release an egg during ovulation

• Uterine cycle: prepares uterus for pregnancy–Menstrual phase (days 1-5): Progesterone levels decline → endometrial lining degenerates → menstruation occurs

–Proliferative (follicular) phase (days 6-14): Estrogen increases → causes endometrial lining to proliferate

–Ovulation (day 14): Induced by high estrogen & LH

–Luteal phase: Corpus luteum produces progesterone (and estrogen) → endometrium proliferates further to prepare for implantation

Menstrual Cycle: Uterine Cycle

Hormonal Control of Endometrium & Menstrual Bleeding

The Corpus Luteum

A. Develops from the ovarian follicle after ovulation

B. Secretes progesterone and estrogen

C. Prepares the uterine endometrium for embryo implantation

• Positive and negative feedback of steroid hormones on the pituitary

–Positive feedback• At the end of follicular growth phase, increasing (i.e.,

very high) estrogen levels cause surge in LH

–Negative feedback• In both follicular and luteal phases, steady (but lower)

levels of estrogen and progesterone inhibit LH and FSH release

Maintenance of Menstrual Cycle

Figure 16.8

Mammalian Egg with Sperm Human Egg with Sperm

Zona Pellucida

Pregnancy

What if the uterus becomes pregnant?

• Sloughing of endometrium would be disastrous for a newly implanted embryo

• Constant supply of progesterone from corpus luteum (CL) is necessary to maintain endometrium

hCG Saves the Embryo

• Newly implanted embryo secretes hCG (human chorionic gonadotropin) which prolongs the lifespan of CL

• CL continues to secrete progesterone which maintains endometrium (and hence fetus)

hCG is the basis of pregnancy test

• hCG is specific (unique) to pregnancy

• The presence of hCG in blood or urine is the basis of a positive test for pregnancy.

The protein hormone that rescues the CL and is the basis of the pregnancy test

A. Relaxin

B. hCG

C. Estrogen

D. FSH

Menopause ends a woman’s reproductive ability

• Main Hypothesis– Ovaries become depleted of eggs

• Many causes of infertility–Number and quality of sperm, pelvic inflammatory

disease (PID), endometriosis

• Enhancing fertility–Options: artificial insemination, in vitro fertilization,

GIFT and ZIFT, fertility enhancing drugs, surrogate mothers

Infertility: Inability to Conceive