Know your cycle to know yourself

The female reproductive system includes internal organs, accessory glands, and external genitalia⁵.

• Ovaries: These are the paired primary reproductive organs in females. They produce eggs and female hormones — estrogen and progesterone. The eggs lie in a protective sac (follicle) where they grow and mature. At birth, females have all the eggs they’ll ever have in their ovaries, but they only begin growing at puberty.

• Uterus: This pear-shaped organ, roughly the size of a fist, houses the growing fetus during pregnancy. It’s much smaller before puberty, after which it grows to about 1.97 to 3.94 inches (5 to 10 cm).

The uterus grows even further during pregnancy, extending to the sides and upward above the belly button. A heart-shaped uterus (bicornuate uterus) is possible but not common. It only appears in 1 in 1000 women.

The uterus has a lining called the endometrium, which varies in thickness throughout the menstrual cycle. It has blood cells, nutrients, and tissues. Without pregnancy, the endometrium breaks down and sheds as menses, approximately 500 times in a woman's lifetime. Fun fact! The uterus manufactures a new organ during pregnancy called the placenta. This nourishes the baby, provides oxygen, and removes waste before their kidneys, lungs, skin, and livers become fully functional at birth.

Although the jaw muscle holds the Guinness world record for the strongest muscle, the uterus is strongest by weight. It generates enough force to push a baby down the birth canal despite being thin.

Interestingly, the uterus is more than just a house for babies. New research reveals that it’s connected to your brain and can affect your ability to remember things. The uterus narrows downward and projects into the vagina forming the cervix.

• Cervix: This is the donut-shaped part of the uterus. It has a central opening that allows menses through and widens during birth to let the baby out. Throughout pregnancy, the cervix forms a mucus plug that secures the baby till it’s time to be born. Hormonal variations throughout the menstrual cycle cause the cervix to undergo several changes. This includes alterations in its shape and secretions. Cervical discharge is vital because it protects the uterus from bacteria and contributes to a woman’s fertility.

• Vagina: This elastic tube continues with the cervix above and opens into the vulva below. Therefore, it connects the external and internal parts of the female reproductive system. The vagina is about 3.15 to 4.72 inches (8 to 12 cm) long.

• Fallopian tubes: These are tubular extensions from the uterus. They end near the ovary and transport eggs to the uterus. It also serves as a site for fertilization.

• Accessory glands: Bartholin's gland, breasts, and skene's gland, are part of the female reproductive system. Bartholin’s glands are found around the vaginal opening, while Skene’s glands open beside the urethra. Both secrete lubricating fluid during sexual stimulation. Breasts or mammary glands produce milk for babies but are involved in sexual activity too.

• Vulva. Everything on the outer female genital area falls under this category. Unfortunately, many adults with limited understanding of the female anatomy say vagina when they really mean the vulva.

Parts of the vulva include the labia minora, labia majora, mons pubis (mons veneris), clitoral acorn, and clitoral prepuce, as well as the urethral outlet and vaginal entrance. The mons pubis is the fat pad over the pubic bone, which serves as a cushion during sexual activity. Labia majora and minora are fleshy tissue folds that enclose and protect the vaginal and urethral openings.

Just as our faces are different, so are our vulvas. A large study examined 657 vulvas under a microscope and found that the most significant feature they had in common was their uniqueness.4 Hence, there’s no need to worry if yours doesn’t look like the textbook or internet images.

• The clitoris (tip of the iceberg): Many scientific and medical textbooks don’t comprehensively describe the anatomy of the clitoris, partly because it was only fully discovered in 1998. This also explains why the clitoris is still relatively unknown in all its glory today. This organ is about 3.15 to 5.51 inches (8 to 13 cm) long and grows throughout your life.

Although you can only see a small button-like lump in the upper part of your vulva, covered by a foreskin, the clitoris has much more underneath. Its job is to make you feel good: It has more than 800 nerve endings, more than anywhere else in the body, and can trigger powerful sensations.

Some say the menstrual cycle has four phases, but it truly has two (follicular and luteal phases). Menstruation and ovulation are key events but fall under the first phase. Here’s what happens during each cycle.

The delicate balance of hormones from the hypothalamus, pituitary gland, and ovaries keeps the menstrual cycle going². Gonadotropin-releasing hormone (GnRH) from the hypothalamus starts the process. It stimulates the pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These pituitary hormones act on the ovaries: FSH drives follicle growth and maturation, while the LH surge triggers ovulation. The ovaries also produce the sex hormones estrogen and progesterone. Hormone levels vary across the cycle: estrogen directs the follicular phase, and progesterone takes over the luteal phase.

If you’re looking for a reason to start tracking your menstrual cycle, here are four.

Basal body temperature (BBT) is your body temperature at rest, taken each morning before you get out of bed⁶. Your BBT varies slightly across the cycle: right after ovulation, increased progesterone from the corpus luteum raises it by about 0.4 to 0.5°F (0.2 to 0.3°C), which tells you ovulation has occurred.

Over 40 years of cycle research and the analysis of over 10 million cycles are behind Daysy. Unlike a regular thermometer, it takes a little longer to record your temperature so the reading is as precise as possible. Because you don't use a separate thermometer or enter the value by hand, it eliminates transcription error.

Daysy determines your non-fertile (green) days with a scientifically confirmed accuracy of 99.4%³. Its algorithm also accounts for factors that can affect your cycle, such as stress, lack of sleep, or alcohol.

The female anatomy is a marvel, and caring for your body begins with learning about it. A woman's reproductive period lasts about 37 years on average⁴, so tracking your cycle supports your overall health: it helps you understand your body, spot unusual changes, learn your patterns, and identify ovulation. Take control of your reproductive health and get to know your cycle with Daysy.