To achieve pregnancy a series of complicated events occurs, which otherwise happens so simply! It is essential to know the normal process so that we can understand the reason; when there is difficulty of getting pregnant.
Ovulation and menstruation – What actually happens?
A woman is born with a lifetime supply of immature eggs in her ovaries. Each month, one matures and is released in a process called ovulation. Ovulation is an important part of the menstrual cycle. In a typical 28-day cycle, a woman's menstrual period begins on day 1. On day 14, ovulation occurs. On day 28, if the egg has not become fertilized, the menstrual cycle begins again with another period.
For ovulation to happen, different parts of the body must all work together. The brain and the ovaries both play roles in this coordination. The ovaries are the two almond-shaped glands sitting within reach of the fallopian tubes. Ovaries produce the eggs as well as the essential sex hormones needed for menstruation and pregnancy.
Just before ovulation, the hypothalamus and pituitary glands in the brain signal the body to start producing hormones. Follicle-stimulating hormone (FSH) prompts fluid-filled chambers in the ovary called follicles to begin growing. In each follicle a single ovum starts growing. Leutinizing hormone (LH) triggers the follicle to rupture when it is matured. In each cycle one ovum is usually released. Women ovulate about 14 days before their next menstrual period would be expected—day 14 on a 28-day cycle. Ovulation occurs within about a day after the surge in LH.
Both FSH and LH play additional roles in the menstrual cycle. They instruct the ovaries to produce estrogen and progesterone, hormones that help ovulation to occur and the uterus to prepare for pregnancy. The uterus is a hollow organ, shaped like a pear and only about three inches long in a non pregnant woman. Its lining, the endometrium, is richly supplied with blood vessels. The endometrium continually renews itself, building up in response to messages sent by estrogen and progesterone.
The Luteinizing Process The menstrual cycle consists of a complex series of events that interact to stimulate ovulation, prepare the uterine lining for a pregnancy, and cause the uterine lining to be shed if pregnancy does not occur. Two glands in the brain, the hypothalamus and the pituitary, send follicle-stimulating hormone (FSH) and luteinizing hormone (LH) to the ovary just before ovulation to stimulate the development of a follicle and its release of an egg into a fallopian tube (ovulation). Follicles are the structures inside the ovary that produce the eggs to be fertilized and that release the hormone estrogen, which stimulates the lining of the uterus to thicken in preparation for pregnancy. After releasing the egg, the empty follicle, called the corpus-luteum, begins producing progesterone. This hormone continues to stimulate the uterine lining to grow and thicken. If the egg is not fertilized, a sudden drop in estrogen and progesterone triggers the uterus to shed its lining and menstruation begins. This marks the start of the next cycle
What actually happens when ovum is fertilized?
For fertilization to occur, healthy sperm must be deposited in a woman's vagina, preferably near the cervix, just about the time of ovulation. Each sperm is about 1/ 1000 inch long; its whip like tail swims up through the cervix, into the uterus, and into the fallopian tubes. Only one sperm is allowed fertilize an egg. Though millions of sperm may start their journey towards the solitary ovum, only a few hundred stay alive during the trip and one fortunate sperm ultimately fertilize the egg.
An egg, which is released during ovulation is usually picked up by the fallopian tube. Women have two fallopian tubes, each about 4 inches long. They are located just above the ovaries and have featherlike fingers called fimbria at their terminals near the ovaries. The fimbria and inner lining of the tubes are lined with cilia, which are like millions of active tiny hairs. These hairs shift the egg from the ovary inside the tubes by suction and cilliary action. An egg is fertilizable for only about 12-72 hours after its release.
The fallopian tubes have smooth tiny musculature throughout their lengths. In the middle, they help by contracting so that the sperm and egg move closer with each other and fertilization happens. At the end nearer the uterus, they are narrow to keep eggs from being released into the uterus too soon.
When sperm are present, they gather around the egg. They discharge enzymes from their heads to help make a hole in the egg to allow penetration. Once one sperm enters the egg, a chemical reaction ensues that pre¬vents other sperm from entering.
In the first half of a woman's menstrual cycle, estrogen makes the endometrial lining begin to thicken with a nutrient rich bedding in case pregnancy should occur. Progesterone then takes over. It is produced mainly in the second half of the cycle by a temporary organ called the corpus luteum. The corpus luteum is formed in the ovary from the follicle that released its egg. Progesterone causes the lining of the uterus to thicken even more. Estrogen and progesterone both play roles in ovulation as well.
If the egg is not fertilized, it dissolves and is absorbed by the body. Then hormone levels drop and the endometrium disintegrates without the hormonal nourishment. This shedding is the monthly menstrual period. The first day of a woman's period is the point at which her hormone levels are at their lowest.
How fertilized ovum is implanted in the uterus?
Inside the fertilized egg, cells begin to divide. If all goes well, the fertilized egg then journeys from the fallopian tube to the uterus where it implants itself in the spongy lining of the uterus. There it grows and develops into an embryo (weeks 2-8), then a fetus for the rest of the pregnancy, and 9 months later, a baby.
Numerous structural and hormonal factors play a part in fertility. What may look like the simplest of human activities—conceiving a baby—can become a miraculous chain of events, especially to a couple having problems getting pregnant.
Basic criteria of a fertile couple
Seven elements are essential to fertility:
1. A woman's ovaries must produce healthy eggs that are released regularly.
2. A man's testicles must be capable of producing healthy sperm that can reach the egg and then penetrate it.
3. During intercourse, the man's semen that contains his sperm has to be deposited at or at least close to the cervix. This puts the sperm in the best position to reach the egg.
4. There has to be a clear passage through the fallopian tube from the ovary to the uterus. This passage is used by both the egg moving down and the sperm moving up. Any obstruction in the fallopian tube interrupts the process of fertilization.
5. The man's sperm have to be able to move freely through the cervix. Any physical or chemical barrier can cause problems.
6. The ovum has 12 to 72 hours of life in which it can be fertilized. The sperm have up to 5 days in which they can fertilize an egg. Timing is critical.
7. Once the egg is fertilized, it has to find a suitable site for implantation in the lining of the uterus.
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