It’s been a long time since your high school anatomy lessons, which were probably your last formal lessons on human reproduction. In the meantime, you may have forgotten much of the basic information. Don’t worry, you’re not alone. Let’s look back and review the fundamentals of the female reproductive system and how conception occurs.
The essential cell of human fertility is the ovum, also known as egg cell, oocyte or gamete. The egg is one of the largest cells in the woman’s body: it is about the size of a grain of sand and is about 16 times larger than a sperm cell.
A woman is born with a finite number of eggs, generally 1-2 million, whose production occurs before birth, in the foetus’ newly-formed womb, around week 20. Do you realise you were in your grandmother’s womb, even before your own mother was born? As opposed to the male foetus, who does not produce sperm in utero, the female foetus has all the eggs that the future woman will ever have. Technically, this means that when your mother was just a foetus in her mother’s uterus, she already had one of the eggs that eventually developed into you.
Until the time when a woman reaches menopause (usually after the age of 50), her eggs have been exhausted. Knowing this, it is easy to understand why age is the most important factor affecting the ovarian reserve.
The female internal reproductive organs are the vagina, uterus, Fallopian tubes, and ovaries.
The vagina is a hollow muscular canal that goes from the vaginal opening to the uterus.
The uterus is shaped like an upside-down pear, has a thick lining and muscular walls. In fact, the uterus contains some of the strongest muscles in a woman’s body. The uterus is the cavity where the foetus will develop. Every month, the endometrium (the inner mucous membrane of the uterus) is thickened with blood and nutritional tissues, preparing for an egg’s implantation if the latter is fertilised by the sperm cell. If the egg doesn’t meet the sperm cell and fertilisation does not occur, the endometrium is shed during menstruation.
At the upper ends of the uterus, two Fallopian tubes connect the uterus and the ovaries. They produce, keep and release eggs into the Fallopian tubes in a process called ovulation. Each tube contains a narrow passage, no larger than the diameter of a sewing needle, which may sometimes be blocked. During each menstrual cycle, an egg is released by one of the ovaries and starts its race downwards to the uterus, through the Fallopian tube. Once the egg reaches the Fallopian tube, the tiny cilia in its lining push it down through the narrow corridor, towards the uterus. If the egg has been fertilised by a sperm cell, we say conception has occurred, but if the egg does not meet the sperm cell, it dies and will be shed along with the uterine lining.
The endocrine system
The endocrine system is the collection of glands secreting hormones straight into the circulatory system to be carried to further target organs. The most important endocrine glands include the pineal gland, the pituitary gland, the pancreas, the ovaries (in women), the testicles (in men), the thyroid, the parathyroid glands, the hypothalamus and the adrenal glands.
As part of the endocrine system, ovaries produce female sex hormones: oestrogen and progesterone. These hormones regulate the menstrual cycle and also play a very important role during pregnancy.
The pituitary gland helps regulate sex hormones through the follicle-stimulating hormone (FSH) and the luteinising hormone (LH). FSH and LH ensure the proper functioning or the reproductive system. FSH stimulates the maturation of ovarian follicles in the ovaries, while LH contributes to ovulation.
Because all components of the human body act in synergy, hormonal balance is extremely important for the reproductive system and for conception.