Life is Sex (Part IV)

How does female sexual function contribute to new human life?

Once the sexual organs have matured so the male can produce sperm and the female can release an egg what is needed for new human life is to join them together to form a zygote (fertilization). The natural way human reproduction takes place is by the male and female coming together in sexual intercourse. This intimate physical union requires the man to insert his erect penis deep into the vagina of the woman and release semen (containing sperm) near the cervical opening of her uterus. Over the next several hours, aided by the cervical mucus, the sperm use their flagella to swim through the body of the uterus toward the fallopian tubes. If one of the woman’s ovaries has released an egg around that time then one of the sperm may be able to penetrate its outer shell to form a zygote. Over the next several hours the zygote develops into an embryo which over the next several days moves into the body of the uterus and implants in its lining. Once implantation takes place the embryo continues to develop and grow into a fetus in a process called gestation and exits the mother’s body nine months later as a new born baby.

Fertility in the female means releasing an egg from her ovary, having it enter the fallopian tube, receiving semen near the cervical opening of her uterus and helping the sperm reach the egg and supporting developing new human life once it implants in the lining of her uterus.

A female has her full complement of immature eggs in her ovaries at birth. To release an egg from the ovary (ovulation) requires her to have enough Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), estrogen and their respective receptors on the cells of her ovary. Monthly ovulation depends on the delicate interplay of her hypothalamus, pituitary and ovary.

Chronic emotional stress, malnutrition, significant fluctuations in weight, serious or recurrent illness and excessive physical exercise can disrupt this balance and cause anovulation. There are also different glandular conditions that can do this too. Also, since the female has a finite number of immature eggs at birth this means that eventually she loses her fertility. This takes place after about thirty or forty years and is called menopause.

If the female has had sexual intercourse around the time she has ovulated then getting the egg to enter the fallopian tube and assisting the sperm to reach it comes into play. By attaching to specific receptors estrogen makes the cells in the cervical opening of the uterus secrete lots of watery mucus. This assists the sperm as they swim through the body of the uterus to the fallopian tubes. Estrogen also causes the fallopian tubes to increase the movement of their cilia (small hair-like projections) and muscle contraction to coax the egg to enter. Once inside, the egg is swept toward the body of the uterus. It is here, within the confined space of the fallopian tube, that the sperm usually meet up with the egg and fertilization takes place. The zygote is then swept along the fallopian tube into the body of the uterus on its way to implantation. 

One common cause of female infertility is sexually transmitted infection. It causes damage to the fallopian tubes and the cervix. The former either can’t capture the egg, let the egg and sperm meet or let the zygote pass through to the body of the uterus. The latter becomes narrowed and sends out abnormal mucus both of which prevent the sperm from moving up into the uterus.

If a sperm is able to fertilize an egg in the fallopian tube and the resulting zygote is able to move into the body of the uterus then providing nutritional support for the developing new human life once it implants in the endometrial lining of the uterus becomes necessary. To do this means having enough estrogen and progesterone and their respective receptors on the lining of the uterus. These hormones tell the lining to develop so it can take care of the embryo. In fact, if pregnancy doesn’t take place, the levels of these sex hormones drops significantly making the lining of the uterus shed in a process called menstruation.

The ovary’s ability to make enough estrogen and progesterone at this stage and defects in the uterus that interfere with implantation or continued gestation are some of the commoner reasons for female infertility.

One can see that everything has to be just right for the female’s ovary to release an egg, coax it into the fallopian tube, help sperm swim to it from the cervix and then provide a haven for the embryo to develop into new human life. 

Three Questions for Mr. Darwin

    1. How did the ovary learn how to develop and release an egg to get new human life?

    2. What taught the fallopian tubes to capture the egg and the cervix to help the sperm?

    3. If both sex hormones and their receptors are needed to develop the uterine lining how could this come have about gradually one step at a time and still allow for new life each step along the way?


Also see Dr. Glicksman's Series on

"Beyond Irreducible Complexity"

"Exercise Your Wonder"

Howard Glicksman M. D. graduated from the University of Toronto in 1978. He practiced primary care medicine for almost 25 yrs in Oakville, Ontario and Spring Hill, Florida. He now practices palliative medicine for a Hospice organization in his community. He has a special interest in how the ethos of our culture has been influenced by modern science’s understanding and promotion of what it means to be a human being.


Copyright 2018 Dr. Howard Glicksman. All rights reserved. International copyright secured.