10:43 10th July 2014 | Ovulation
Ovulation Menstrual Cycle Human Reproduction FSH Corpus Luteum Follicle Fertilisation primordial Follicles
Ovulation is the process in a female’s menstrual cycle during which a mature oocyte (egg) is released from the ovary. This process is essential to human reproduction and the physiological changes that occur in the woman to achieve ovulation and reproduction is called the menstrual cycle. The average menstrual cycle lasts for 28 days (the beginning of one menstrual bleed to the beginning of the next one) but it may be as short as 14 days and as long as 42 days. Generally speaking ovulation (release of the egg) occurs in the middle of the cycle plus or minus two days, that is, 14 days (12 – 16 days) in a 28-day cycle.
What controls ovulation?
Women are born with the total number of eggs that they will ever have. The average woman is born with approximately 1.5 million eggs and this number gradually declines to about 800,000 at puberty when the woman commences her reproductive life. The eggs are in a state of arrested development and are called primordial follicles. They remain in this state until a cohort is recruited by critical blood levels of Follicle Stimulating Hormone (FSH). FSH is a hormone released from the anterior part of the pituitary gland at the base of the brain. In response to FSH, the, the ovarian follicle will undergo a series of transformations from the state of arrested development to the mature oocyte just before ovulation. Ovulation is triggered by a spike in the amount of FSH as well as the levels of luteinizing hormone (LH) also released by the pituitary gland.
Ovulation occurs when the most mature egg in the cohort is released from the ovary into the abdominal cavity, from where it is picked up by the Fallopian tubes and transported towards the uterine cavity. Fertilisation occurs within the fallopian tubes. The rising levels of FSH in addition to stimulating the development of the egg, prepares the lining of the uterus to be able to receive a fertilized egg. If no conception occurs, the uterine lining as well as blood will be shed in menstruation.
After ovulation, the follicle is transformed into the corpus luteum; the term refers to the visible collection of blood left after rupture of the follicle that secretes progesterone. The corpus luteum is essential for establishing and maintaining pregnancy in females. The corpus luteum secretes progesterone which is responsible for developing and maintaining the lining of the womb for pregnancy.
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