Chapter 17 Female Reproduction

The Female Reproductive System Produces Eggs and Nurtures the Embryo and Fetus

FIGURE 17.6a The female reproductive system

FIGURE 17.6b The female reproductive system

TABLE 17.3 REVIEW OF FEMALE REPRODUCTIVE SYSTEM

Female Reproductive System 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

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

FIGURE 17.8 The ovarian cycle. A follicle does not move around the ovary during its development, as depicted here. The steps indicate the sequence of events that occurs in a single place in the ovary during the approximately 28-day cycle.

Mature (Graafian) Follicle

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

Menstrual Cycle: Ovarian Cycle 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

FIGURE 17.9 The ovarian and uterine cycles are coordinated by the interplay of hormones from the anterior pituitary gland and the ovary. The timing of events shown is for a 28-day cycle.

Ovarian follicles Are stimulated to develop by FSH Contain a single egg Secrete estrogen Release an egg during ovulation

Menstrual Cycle: Uterine Cycle 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

FIGURE 17.9 The ovarian and uterine cycles are coordinated by the interplay of hormones from the anterior pituitary gland and the ovary. The timing of events shown is for a 28-day cycle.

Table: 17-T05 Title: Ovarian and uterine cycles. Caption:

Hormonal Control of Endometrium & Menstrual Bleeding

TABLE 17.4 REVIEW OF HORMONES INVOLVED IN THE REGULATION OF FEMALE REPRODUCTIVE PROCESSES

FIGURE 17.9 The ovarian and uterine cycles are coordinated by the interplay of hormones from the anterior pituitary gland and the ovary. The timing of events shown is for a 28-day cycle.

The Corpus Luteum Develops from the ovarian follicle after ovulation Secretes progesterone and estrogen Prepares the uterine endometrium for embryo implantation

Maintenance of Menstrual Cycle 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

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 Relaxin hCG Estrogen FSH

Menopause ends a woman’s reproductive ability Main Hypothesis Ovaries become depleted of eggs

Infertility: Inability to Conceive 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