Female Reproductive System and Hormones

The process of egg cell development in females, involving stages like oogonia, primary oocyte, secondary oocyte, and ovum.

A monthly cycle controlled by hormones, where an egg matures and is released from the ovary.

Hormones like estrogen and progesterone regulate the ovarian cycle, influencing ovulation, menstruation, and fertility.

The ability of a woman to become pregnant, influenced by age, health, and ovulation.

Methods to prevent pregnancy, including hormonal, barrier, and surgical options.

The natural cessation of menstruation, marking the end of a woman's reproductive years.

The union of a sperm and an egg, forming a zygote, the first cell of a new individual.

The journey from a zygote into a fetus, involving growth, cell division, and organ formation.

Protective layers surrounding the fetus, providing nutrients and removing waste.

The process of a baby's birth, involving contractions, dilation, and pushing.

Ovaries are the female gonads, responsible for producing oocytes (eggs) and sex hormones like estrogen and progesterone.

Fertilization typically happens in the uterine (Fallopian) tubes, where the fimbriae capture the ovulated egg.

The endometrium is the inner lining of the uterus, where a fertilized egg implants and develops.

The myometrium is the muscular middle layer of the uterus, responsible for contracting during childbirth to push the baby out.

The vagina is the canal that connects the uterus to the outside, serving as the birth canal and the site of sexual intercourse.

Homologous structures are body parts in different species that have similar underlying anatomy, suggesting shared ancestry.

Atresia is the programmed death of primordial follicles in the ovary during childhood, resulting in loss of potential eggs.

Meiosis I in oocyte development is paused at prophase I until puberty, ensuring a limited supply of mature eggs released throughout a woman's reproductive years.

After meiosis II starts, it stops at metaphase II and will only complete if fertilization occurs.

Oogonia are the earliest stage of egg development, while primary oocytes have begun meiosis I and are arrested at prophase I.

The ovarian cycle has three phases: the follicular phase, ovulation, and the luteal phase. These phases involve follicle development, egg release, and hormonal changes.

During the follicular phase, primary follicles mature into secondary follicles and then into a Graafian follicle. The dominant Graafian follicle produces increasing levels of estradiol (estrogen).

FSH stimulates the follicles to grow and mature. It also increases the number of FSH receptors on the follicles, making them more sensitive to FSH.

Estradiol (estrogen) is produced by granulosa cells in the follicles and increases in concentration throughout the follicular phase. It also stimulates the hypothalamus to release more GnRH, eventually leading to an LH surge.

The LH surge is a spike in luteinizing hormone (LH) that occurs around day 12-14 of the menstrual cycle. It's triggered by high estradiol levels and is crucial for ovulation.

The LH surge causes the Graafian follicle to rupture and release the secondary oocyte (egg) from the ovary. This is the actual release of the egg.

After ovulation, the ruptured follicle transforms into the corpus luteum. This structure produces progesterone and estradiol.

The corpus luteum secretes progesterone and estradiol, which prepare the uterus for potential pregnancy. High levels of these hormones also feedback to the pituitary gland, inhibiting FSH and LH.

If fertilization doesn't occur, the corpus luteum degenerates, leading to a decrease in progesterone and estradiol. This triggers menstruation.

The luteal phase is the period after ovulation when the corpus luteum forms and produces progesterone and estradiol. This phase prepares the uterus for potential pregnancy and is usually around 14 days long.

The corpus luteum, responsible for progesterone production, typically degenerates around day 28 of the menstrual cycle if fertilization doesn't occur. This decline in progesterone triggers the shedding of the uterine lining, resulting in menstruation.

Menstruation, the shedding of the uterine lining, is triggered by a decrease in the levels of estradiol and progesterone produced by the degenerating corpus luteum. This hormonal shift signals the body to shed the thickened lining that was prepared for a potential pregnancy.

Oral contraceptives mimic progesterone, the hormone that prevents ovulation. They essentially trick the body into thinking it's already in the luteal phase, thus suppressing ovulation and preventing pregnancy.

LARCs are highly effective forms of birth control that provide long-term protection against pregnancy. Two common types include intrauterine devices (IUDs) and subdermal hormonal implants. IUDs work by preventing fertilization, while implants release progestin to inhibit ovulation and thicken cervical mucus.

The rhythm method relies on tracking a woman's menstrual cycle to predict ovulation. By avoiding intercourse during the fertile window, this natural method aims to prevent pregnancy.

Menopause is the natural cessation of ovarian activity, leading to the end of menstrual cycles. It typically occurs around age 50 and results from changes in the ovaries themselves, not a decrease in FSH and LH.

FSH and LH levels actually increase during menopause due to a lack of negative feedback from the ovaries. Without the ovaries producing estrogen, their usual feedback mechanism to suppress FSH and LH production is absent, leading to their elevation.

Menopause symptoms are primarily caused by a drop in estrogen levels. This includes hot flashes, vaginal dryness, and an increased risk of osteoporosis and atherosclerosis.

Managing menopause symptoms often involves hormone replacement therapy (HRT) to supplement estrogen levels. Lifestyle changes such as exercise, a healthy diet, and stress management can also help alleviate symptoms.