The Anatomy of Ovulation: Just the Facts, Figures, Graphs & Pictures
To fully understand ovulation – defined most generally as the process by which an egg matures and is released by the ovary – it does not hurt to learn the details underlying these often complicated processes. This article is dedicated to examining the basics of reproductive anatomy and the processes of the menstrual cycle that govern ovulation. But instead of a wordy (boring) description of technical details, we’ll present some images, definitions, and graphs that represent the interplay of anatomy and hormones, as well as some interesting facts that might prove useful when it comes to predicting ovulation and achieving pregnancy.
The Ovarian Follicle/Corpus Luteum: Ovarian follicles contain the female ova or eggs. During the first stages of a woman’s cycle, the ovarian follicle develops and matures an ovum (folliculogenesis), culminating in ovulation – the release of the egg. Following ovulation, the follicle becomes corpus luteum and serves to produce progesterone. In the image (see in context above), maturation stages of the ovarian follicle are represented by the various bluish circles. The larger blue follicle represents a mature follicle and ova ready to be expelled into the fallopian tube. The “collapsed” circles near the top represent the luteal body or corpus luteum.
The Fallopian Tube: The fallopian tubes extend off the upper sides of the uterus and lead up to the ovaries. They have 20 to 25 finger-like structures on their ends that hover just above the ovaries and work to collect the mature egg when it is released. It is in the fallopian tubes that fertilization of the egg will take place.
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The Uterus / Womb: The uterus is the reproductive organ commonly know as the womb. The uterus provides a home for a developing baby during pregnancy. The uterus is composed of linings and layers that change during a woman’s cycle. See endometrium below.
The Endometrium: The endometrium (or uterine lining) is a layer of uterus in which a fertilized egg will implant
The Cervix: Situated between the vagina and womb, sperm must pass through the cervix (or cervical canal) in order to pass into the uterus. During a woman’s fertile time, the cervix produces “fertile” cervical fluids that promote sperm movement and longevity. During non-fertile times of the month, the cervix may produce “non-fertile” mucus to protect the uterus from infection.
Hormone Changes and Ovulation: This graph sums up what is going on in your body, hormonally-speaking, as you move through your monthly cycle. This representation presents an average twenty-eight day cycle with the ovulation-day taking place on day-fourteen. The reality, for many women, is a longer or shorter cycle, and when it comes to the menstrual cycle (as with most other categories of life) “average” should not be equated with “normal”. Cycle lengths (and ovulation-dates) do different substantially among various women.
The color of the graph indicates changes in body temperature due hormone fluctuation – from the cool stage of the ovulatory cycle (days 1-14) to the warm stage of the luteal phase (days 15- 28). The cooler stage is dominated by the dominance of estrogens (estradiol / purple line), while the hot phase is usurped by progesterone (green line). The former prepares the body for conception (thickens the endometrium with blood vessel and tissues) while the latter warms the body and helps maintain a pregnancy once a fertilized egg implants in the womb.
Also note the gray line – this represents your basal body temperature; your bbt thermal shift typically becomes measurable approximately 24 hours after you ovulate. Change in bbt temperature correlates with changes in progesterone levels, as progesterone is the “causal hormone” of the thermal shift. By measuring your daily basal temperature, you can determine when you ovulate during your cycle.
Other significant hormonal agents represented in the image include FSH (blue line), which stimulates the ovarian follicles (ova or eggs) to mature; notice how it crests around the first week of the cycle. The most “radical” of the hormones, so to speak, is LH – the red line – which moves into action to help initiate ovulation; LH erodes the wall of the ovarian follicle producing a “stigma” or hole through which the ovum is released.
To summarize, FSH and estrogen hormones are prominent during the first weeks of the cycle, toning the uterus and helping the follicle develop and the ovum mature. Near midcycle, LH is released to help stimulate ovulation. On day fourteen (on the graph), ovulation takes place and the egg bursts into the fallopian tube and is swept toward the uterus. At this juncture, the follicle becomes the corpus luteum – whose duty it is to produce progesterone. With the rise of this hormone in your system, your body warms and you are able to detect a thermal shift using a basal thermometer.
Helpful TTC Notes for Looking at Ovulation and Your Menstrual Cycle
• Fertility: Once you ovulate, the egg must be fertilized within about twelve to twenty-four hours. This is the maximum post-ovulatory life span of the ovum. However, you are technically “fertile” in the days prior to ovulation as well, due to the fact sperm may survive a number of days in the womb (waiting). Most fertility experts advise that you “time lovemaking” for the handful of days right before you ovulate, as well as the expected day of.
• Timing Lovemaking: To anticipate when you ovulate, there are many predictive methods – from using a basal thermometer (discussed above) and keeping an ovulation calendar to using tests that track the various hormonal surges represented in the chart. For example, Lh (red line) offers a very clear and sudden surge that can be detected through urine ovulation tests, letting you know that your ovulation-day is imminent.
• How often? In most cases, only one egg is discharged each cycle. In the case of fraternal twins, of course, more than one ovum can be discharged. There is conflicting data regarding ovulating more than one a month. Most fertility experts agree that women can expect to ovulate once per month, or menstrual cycle, typically near the midpoint.
• Cycle Regularity: There are many factors that can alter the regularity of the menstrual cycle and therefore the regularity of an ovulation-date. These include changes in the balance of hormones, illnesses, travel, stress, extended bouts of insomnia, dietary factors, etc. Some women have clockwork cycles, but many do not. Cycle irregularity or changes in cycle length are common. If you are concerned about cycle regularity, it is advised to discuss the matter with your doctor.
• Pregnancy: Once an egg is discharged, conception occurs when a single sperm fertilizes the egg. At that moment you have conceived. For a successful pregnancy to occur, the fertilized egg must implant in the uterine lining. This typically takes place, on average, about a week after you ovulate. The technical term is “implantation”.
• Missed Periods: If you become pregnant, your progesterone levels will stay high and you will not menstruate (e.g., you will miss your period). If pregnancy is not achieved, the corpus luteum stops producing the hormone and menstruation follows – you have your period – and the next cycle begins.
• Ouch. Can you feel when you ovulate? Some women do. But not all. Ovulation pains occur in some women as sharp pains in the lower abdomen.
• Spotting: It’s unlikely that ovulation will cause spotting, though in some rarer cases it is classified as a sign. It’s possible to experience light, brownish spotting shortly after you ovulate. This should not be confused with implantation bleeding, which is a more likely occurrence (and pregnancy symptom) which takes place a week or so after you ovulate.