The Female Reproductive System, Explained Without the Textbook Jargon

You are born with all the eggs you will ever have — roughly one to two million at birth, though only a few hundred will ever mature and be released. Each month, usually one egg matures inside a fluid-filled sac called a follicle. When that follicle ruptures, the egg is released. That is ovulation.

Ovaries also make estrogen and progesterone. Estrogen helps rebuild the uterine lining after a period, supports bone density, and influences mood and libido. Progesterone rises after ovulation to stabilize the lining in case of pregnancy. When pregnancy does not occur, progesterone drops and your period starts.

If you are trying to conceive, knowing roughly when ovulation happens matters — our ovulation calculator can estimate timing from your last period, though blood tests or ultrasound at a clinic are more precise.

After ovulation, tiny hair-like structures inside the tube help sweep the egg toward the uterus. Fertilization — when a sperm cell joins the egg — typically happens in the fallopian tube, not in the uterus itself. The fertilized egg then travels toward the uterus over several days before attempting to implant.

Pelvic infections such as untreated chlamydia or gonorrhea can scar or block fallopian tubes. That is one reason STI testing and prompt treatment matter even when symptoms are mild. Endometriosis and prior surgery can also affect tube function and fertility.

Think of the uterine lining like wallpaper that gets repainted every month. Estrogen thickens it with blood-rich tissue. After ovulation, progesterone holds that lining steady. If a fertilized egg implants, the lining stays. If not, hormone levels fall and the lining breaks down — that is menstrual bleeding.

Periods vary widely and still be normal. What matters is what is normal for you changing suddenly, or bleeding that interferes with daily life.

The cervix is the lower opening of the uterus into the vagina. Its mucus changes through the cycle — around ovulation it often becomes clearer and stretchier, which helps sperm travel. A Pap smear screens the cervix for abnormal cells that could lead to cancer; it is not the same as an STI test, and you need both at different intervals.

The vulva is everything external: labia, clitoris, and the openings of the urethra and vagina. The vagina is the internal canal. Pain, itching, or lumps in different spots can point to different causes — being specific about location helps your clinician.

In the follicular phase (from the first day of your period through ovulation), estrogen rises. The uterine lining rebuilds and an egg matures in the ovary. Many people feel more energy during this stretch.

Ovulation is the midpoint for most people: a surge of luteinizing hormone (LH) triggers the follicle to release the egg. Some feel a one-sided twinge; many feel nothing at all.

In the luteal phase (after ovulation until your next period), progesterone dominates. If pregnancy does not occur, levels drop, the lining sheds, and the cycle begins again. Some people notice bloating, breast tenderness, or mood shifts in the days before bleeding — often called PMS.

You do not need to wait for a crisis. A first gynecology visit is reasonable in the teens for questions about periods, contraception, or pain — and ongoing care helps catch problems early.

Related guides: medications and fertility · finding your fertile window · endometriosis and painful sex