Ovulation is the process in the menstrual cycle by which a mature ovarian follicle ruptures and discharges an
ovum (also known as an oocyte, female gamete, or casually, an egg) that participates in reproduction. Ovulation
also occurs in the estrous cycle of other animals, which differs in many fundamental ways to the menstrual cycle.
ovum (also known as an oocyte, female gamete, or casually, an egg) that participates in reproduction. Ovulation
also occurs in the estrous cycle of other animals, which differs in many fundamental ways to the menstrual cycle.
The process of ovulation is controlled by the hypothalamus of the brain and through the release of hormones
secreted in the anterior lobe of the pituitary gland, (LH and FSH). In the follicular (pre-ovulatory) phase of the
menstrual cycle, the ovarian follicle will undergo a series of transformations called cumulus expansion, this is
stimulated by the secretion of FSH. After this is done, a hole called the stigma will form in the follicle, and the ovum
will leave the follicle through this hole. This release of ovum, ovulation is triggered by a spike in the amount of FSH
and LH released from the pituitary gland. During the luteal (post-ovulatory) phase, the ovum will travel through the
fallopian tubes toward the uterus, implanting there 6-12 days later if fertilized, or degrading in the fallopian tubes
within 24 hours if not fertilized.
In humans, the few days near ovulation constitute the fertile phase. The average time of ovulation is the fourteenth
day of an average length (twenty-eight day) menstrual cycle. It is normal for the day of ovulation to vary from the
average, with ovulation anywhere between the tenth and nineteenth day being common.
Cycle length alone is not a reliable indicator of the day of ovulation. While in general an earlier ovulation will result in
a shorter menstrual cycle, and vice versa, the luteal (post-ovulatory) phase of the menstrual cycle may vary by up to
a week between women.
secreted in the anterior lobe of the pituitary gland, (LH and FSH). In the follicular (pre-ovulatory) phase of the
menstrual cycle, the ovarian follicle will undergo a series of transformations called cumulus expansion, this is
stimulated by the secretion of FSH. After this is done, a hole called the stigma will form in the follicle, and the ovum
will leave the follicle through this hole. This release of ovum, ovulation is triggered by a spike in the amount of FSH
and LH released from the pituitary gland. During the luteal (post-ovulatory) phase, the ovum will travel through the
fallopian tubes toward the uterus, implanting there 6-12 days later if fertilized, or degrading in the fallopian tubes
within 24 hours if not fertilized.
In humans, the few days near ovulation constitute the fertile phase. The average time of ovulation is the fourteenth
day of an average length (twenty-eight day) menstrual cycle. It is normal for the day of ovulation to vary from the
average, with ovulation anywhere between the tenth and nineteenth day being common.
Cycle length alone is not a reliable indicator of the day of ovulation. While in general an earlier ovulation will result in
a shorter menstrual cycle, and vice versa, the luteal (post-ovulatory) phase of the menstrual cycle may vary by up to
a week between women.
Ovulation - Definition
Summation
Detecting Ovulation
The start of ovulation can be detected by various signs. Because the signs are not readily discernible by people
other than the woman herself, humans are said to have a concealed ovulation.
Women near ovulation experience changes in the cervix, in mucus produced by the cervix, and in their basal body
temperature. Furthermore, many women also experience secondary fertility signs including Mittelschmerz (pain
associated with ovulation) and a heightened sense of smell.
Many women experience heightened sexual desire in the several days immediately before ovulation. One study
concluded that women subtly improve their facial attractiveness during ovulation.
Ovulation Calculator
other than the woman herself, humans are said to have a concealed ovulation.
Women near ovulation experience changes in the cervix, in mucus produced by the cervix, and in their basal body
temperature. Furthermore, many women also experience secondary fertility signs including Mittelschmerz (pain
associated with ovulation) and a heightened sense of smell.
Many women experience heightened sexual desire in the several days immediately before ovulation. One study
concluded that women subtly improve their facial attractiveness during ovulation.
Ovulation Calculator
The majority of hormonal contraceptives and conception boosters focus on the ovulatory phase of the menstrual
cycle because it is the most important determinant of fertility. Hormone therapy can positively or negatively interfere
with ovulation and can give a sense of cycle control to the woman.
Follicle stimulating hormone, gonadotropin releasing hormone (GnRH), and estradiol have been purified in the
laboratory. Chemical analogues of estradiol and progesterone have also been synthesized. Recall that GnRH is an
upstream inducer of both FSH and LH secretion.
Generally, administered FSH or GnRH can induce ovulation by rapidly accelerating the pace of folliculogenesis,
allowing for conception. Estradiol and progesterone, taken in various forms including combined oral contraceptive
pills, mimics the hormonal levels of the menstrual cycle and engage in negative feedback of folliculogenesis and
ovulation.
Ovulation induction is a promising assisted reproductive technology for patients with conditions such as polycystic
ovary syndrome (PCOS) and oligomenorrhea.
Medications that are commonly prescribed to induce ovulation include Clomid, Gonal-F/Follistim AQ, Metformin,
Bravelle, Menopur and Repronex.
All ovulation-inducing medications carry the risk of side effects. A recent study has raised the possibility of a link
between ovulation-inducing agents and an increased risk of ovarian carcinoma.
cycle because it is the most important determinant of fertility. Hormone therapy can positively or negatively interfere
with ovulation and can give a sense of cycle control to the woman.
Follicle stimulating hormone, gonadotropin releasing hormone (GnRH), and estradiol have been purified in the
laboratory. Chemical analogues of estradiol and progesterone have also been synthesized. Recall that GnRH is an
upstream inducer of both FSH and LH secretion.
Generally, administered FSH or GnRH can induce ovulation by rapidly accelerating the pace of folliculogenesis,
allowing for conception. Estradiol and progesterone, taken in various forms including combined oral contraceptive
pills, mimics the hormonal levels of the menstrual cycle and engage in negative feedback of folliculogenesis and
ovulation.
Ovulation induction is a promising assisted reproductive technology for patients with conditions such as polycystic
ovary syndrome (PCOS) and oligomenorrhea.
Medications that are commonly prescribed to induce ovulation include Clomid, Gonal-F/Follistim AQ, Metformin,
Bravelle, Menopur and Repronex.
All ovulation-inducing medications carry the risk of side effects. A recent study has raised the possibility of a link
between ovulation-inducing agents and an increased risk of ovarian carcinoma.
Assisted Ovulation
Phases of the Menstrual Cycle
Menstruation
Menstruation is also called menstrual bleeding, menses, or a period. This bleeding serves as a sign that a woman
has not become pregnant. (However, this cannot be taken as certainty, as sometimes there is some bleeding in
early pregnancy.) During the reproductive years, failure to menstruate may provide the first indication to a woman
that she may have become pregnant. A woman might say that her "period is late" when an expected menstruation
has not started and she might have become pregnant.
Eumenorrhea denotes normal, regular menstruation that lasts for a few days (usually 3 to 5 days, but anywhere
from 2 to 7 days is considered normal).
The average blood loss during menstruation is 35 millilitres with 10-80 mL considered normal;
many women also notice shedding of the endometrium lining that appears as tissue mixed with the blood. An
enzyme called plasmin — contained in the endometrium — tends to inhibit the blood from clotting. Because of this
blood loss, women have higher dietary requirements for iron than do males to prevent iron deficiency. Many
women experience uterine cramps during this time. (Severe cramps or other symptoms are called dysmenorrhea.)
A vast industry has grown to provide sanitary products to help women to manage their menses.
Menstruation is also called menstrual bleeding, menses, or a period. This bleeding serves as a sign that a woman
has not become pregnant. (However, this cannot be taken as certainty, as sometimes there is some bleeding in
early pregnancy.) During the reproductive years, failure to menstruate may provide the first indication to a woman
that she may have become pregnant. A woman might say that her "period is late" when an expected menstruation
has not started and she might have become pregnant.
Eumenorrhea denotes normal, regular menstruation that lasts for a few days (usually 3 to 5 days, but anywhere
from 2 to 7 days is considered normal).
The average blood loss during menstruation is 35 millilitres with 10-80 mL considered normal;
many women also notice shedding of the endometrium lining that appears as tissue mixed with the blood. An
enzyme called plasmin — contained in the endometrium — tends to inhibit the blood from clotting. Because of this
blood loss, women have higher dietary requirements for iron than do males to prevent iron deficiency. Many
women experience uterine cramps during this time. (Severe cramps or other symptoms are called dysmenorrhea.)
A vast industry has grown to provide sanitary products to help women to manage their menses.
Follicular phase - The fertile phase
Through the influence of a rise in Follicle stimulating hormone (FSH), five to seven tertiary-stage ovarian follicles
are recruited for entry into the next menstrual cycle. These follicles, that have been growing for the better part of a
year in a process known as folliculogenesis, compete with each other for dominance. In a signal cascade kicked off
by luteinizing hormone (LH), the follicles secrete estradiol, a steroid that acts to inhibit pituitary secretion of FSH.
While estradiol inhibits pituitary secretion of FSH, it acts locally on the follicle by making it more sensitive to FSH by
increasing FSH receptors. With diminished FSH supply comes a slowing in growth that eventually leads to follicle
death, known as atresia. The largest follicle secretes inhibin that serves as a finishing blow to less competent
follicles by further suppressing FSH. This dominant follicle continues growing, forms a bulge near the surface of
the ovary, and soon becomes competent to ovulate.
The oestradiol, along with other oestrogens that follicles secrete, also initiate the formation of a new layer of
endometrium in the uterus, histologically identified as the proliferative endometrium. If fertilized, the embryo will
implant itself within this hospitable flesh.
Through the influence of a rise in Follicle stimulating hormone (FSH), five to seven tertiary-stage ovarian follicles
are recruited for entry into the next menstrual cycle. These follicles, that have been growing for the better part of a
year in a process known as folliculogenesis, compete with each other for dominance. In a signal cascade kicked off
by luteinizing hormone (LH), the follicles secrete estradiol, a steroid that acts to inhibit pituitary secretion of FSH.
While estradiol inhibits pituitary secretion of FSH, it acts locally on the follicle by making it more sensitive to FSH by
increasing FSH receptors. With diminished FSH supply comes a slowing in growth that eventually leads to follicle
death, known as atresia. The largest follicle secretes inhibin that serves as a finishing blow to less competent
follicles by further suppressing FSH. This dominant follicle continues growing, forms a bulge near the surface of
the ovary, and soon becomes competent to ovulate.
The oestradiol, along with other oestrogens that follicles secrete, also initiate the formation of a new layer of
endometrium in the uterus, histologically identified as the proliferative endometrium. If fertilized, the embryo will
implant itself within this hospitable flesh.
Ovulation
When the follicle has matured, it secretes enough estradiol to trigger the acute release of luteinizing hormone (LH).
In the average cycle this LH surge starts around cycle day 12 and may last 48 hours. The release of LH matures the
egg and weakens the wall of the follicle in the ovary. This process leads to ovulation: the release of the now mature
ovum, the largest cell of the body (with a diameter of about 0.5 mm). Which of the two ovaries — left or right —
ovulates appears essentially random; no known left/right co-ordination exists. The Fallopian tube needs to capture
the egg and provide the site for fertilization. A characteristic clear and stringy mucus exhibiting spinnbarkeit
develops at the cervix, ready to accept sperm from intercourse. In some women, ovulation features a characteristic
pain called Mittelschmerz (German term meaning 'middle pain') which lasts for several hours. The sudden change in
hormones at the time of ovulation also causes light mid-cycle bleeding for some women. Many women perceive the
vaginal and cervical mucus changes at ovulation, particularly if they are monitoring themselves for signs of fertility.
An unfertilized egg will eventually disintegrate or dissolve in the uterus. Scientific investigations have indicated that
the olfactory acuity or the sense of smell is greatest during ovulation in women.
When the follicle has matured, it secretes enough estradiol to trigger the acute release of luteinizing hormone (LH).
In the average cycle this LH surge starts around cycle day 12 and may last 48 hours. The release of LH matures the
egg and weakens the wall of the follicle in the ovary. This process leads to ovulation: the release of the now mature
ovum, the largest cell of the body (with a diameter of about 0.5 mm). Which of the two ovaries — left or right —
ovulates appears essentially random; no known left/right co-ordination exists. The Fallopian tube needs to capture
the egg and provide the site for fertilization. A characteristic clear and stringy mucus exhibiting spinnbarkeit
develops at the cervix, ready to accept sperm from intercourse. In some women, ovulation features a characteristic
pain called Mittelschmerz (German term meaning 'middle pain') which lasts for several hours. The sudden change in
hormones at the time of ovulation also causes light mid-cycle bleeding for some women. Many women perceive the
vaginal and cervical mucus changes at ovulation, particularly if they are monitoring themselves for signs of fertility.
An unfertilized egg will eventually disintegrate or dissolve in the uterus. Scientific investigations have indicated that
the olfactory acuity or the sense of smell is greatest during ovulation in women.
Luteal phase
The corpus luteum is the solid body formed in the ovaries after the egg has been released from the fallopian tube
which continues to grow and divide for a while. After ovulation, the residual follicle transforms into the corpus luteum
under the support of the pituitary hormones. This corpus luteum will produce progesterone in addition to estrogens
for approximately the next 2 weeks. Progesterone plays a vital role in converting the proliferative endometrium into a
secretory lining receptive for implantation and supportive of the early pregnancy. It raises the body temperature by
one-half to one degree Fahrenheit (one-quarter to one-half degree Celsius), thus women who record their
temperature on a daily basis will notice that they have entered the luteal phase. If fertilization of an egg has
occurred, it will travel as an early blastocyst through the fallopian tube to the uterine cavity and implant itself 6 to 12
days after ovulation. Shortly after implantation, the growing embryo will signal its existence to the maternal system.
One very early signal consists of human chorionic gonadotropin (hCG), a hormone that pregnancy tests can
measure. This signal has an important role in maintaining the corpus luteum and enabling it to continue to produce
progesterone. In the absence of a pregnancy and without hCG, the corpus luteum demises and inhibin and
progesterone levels fall. This will set the stage for the next cycle. Progesterone withdrawal leads to menstrual
shedding (progesterone withdrawal bleeding), and falling inhibin levels allow FSH levels to rise to raise a new crop of
follicles.
The corpus luteum is the solid body formed in the ovaries after the egg has been released from the fallopian tube
which continues to grow and divide for a while. After ovulation, the residual follicle transforms into the corpus luteum
under the support of the pituitary hormones. This corpus luteum will produce progesterone in addition to estrogens
for approximately the next 2 weeks. Progesterone plays a vital role in converting the proliferative endometrium into a
secretory lining receptive for implantation and supportive of the early pregnancy. It raises the body temperature by
one-half to one degree Fahrenheit (one-quarter to one-half degree Celsius), thus women who record their
temperature on a daily basis will notice that they have entered the luteal phase. If fertilization of an egg has
occurred, it will travel as an early blastocyst through the fallopian tube to the uterine cavity and implant itself 6 to 12
days after ovulation. Shortly after implantation, the growing embryo will signal its existence to the maternal system.
One very early signal consists of human chorionic gonadotropin (hCG), a hormone that pregnancy tests can
measure. This signal has an important role in maintaining the corpus luteum and enabling it to continue to produce
progesterone. In the absence of a pregnancy and without hCG, the corpus luteum demises and inhibin and
progesterone levels fall. This will set the stage for the next cycle. Progesterone withdrawal leads to menstrual
shedding (progesterone withdrawal bleeding), and falling inhibin levels allow FSH levels to rise to raise a new crop of
follicles.
Planning Your Pregnancy - All About Ovulation
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