Fertility is something that concerns most couples at some point in their relationship. For some couples, it is easy to achieve pregnancy and they don't need to think about the different aspects that play a role. Even though experiencing difficulty getting pregnant can be frustrating and result in self blame, it is important to note that it is more common than most people perceive. 1 in 6 couples will have some degree of infertility issue. Therefore, it is not that uncommon and many couples have to deal with some degree of it. In some cases it is more difficult to treat but it is important to not lose hope. Both egg and sperm can play a role in infertility and so both reproductive systems need to be analysed extensively. Here, we'll have a very brief look at the reproductive systems and will focus on them individually and in more detail in future posts.
Female reproductive system
Let's start with a brief description of the female's reproductive system and the things that can go wrong. Every woman is born with a limited number of eggs as most have undergone atresia (cellular death). The remaining eggs are arrested at a point in their development and stored until the woman reaches the age of puberty. After puberty is reached, in a healthy woman with regular cycles, an egg or two is released from the ovaries each month. With each cycle, 3-30 eggs are recruited for growth, during which 1 or 2 mature and are released from the ovary. The other recruited eggs undergo cellular death. If there is sperm available in the Fallopian tubes, the egg can become fertilized at which stage it resumes its development and incorporates the sperm's genetic material. If sperm is not available, the egg is shed along with the uterine lining in the corresponding menstrual bleed. If an egg becomes fertilized and grows to a blastocyst embryo, it proceeds to the uterine lining where it can potentially implant and result in a pregnancy. The growth of the fertilized egg and the following implantation also represents it's own set of complications that can contribute to infertility.
Hormonal changes in a menstrual cycle
There are a variety of hormonal fluctuations which need to be in the correct synchronicity in order to have regular menstrual cycles with regular egg release. A small part of the brain (hypothalamus) is responsible for secreting gonadotrophin-releasing hormone (GnRH) which regulates the secretion of gonadotrophins (Luteinizing hormone - LH and follicle-stimulating hormone - FSH) from the anterior pituitary (another portion of the brain). These hormones are released in pulses every few hours. They together can stimulate the ovaries and induce ovulation of an egg. They also induce the secretion of estradiol and progesterone from the ovaries. We'll have a more detailed look at the hormonal axis in later posts.
Male Reproductive system
The male reproductive system also plays an important role in a couple's ability to achieve a pregnancy. Starting at puberty, the male body is capable of producing sperm. The process of sperm production takes approximately 3 months and unlike the women's finite egg store, the male reproductive system is capable of continuously producing new sperm. Let's have a brief look at the hormonal axis of sperm production in males.
Hormonal aspect
The hypothalamus releases GnRH in a pulsatile fashion which works on the anterior pituitary to release LH and FSH. The LH then signals leydig cells in a specific part of the testicles to produce testosterone. The testosterone then signals sertoli cells to initiate spermatogenesis and maturation of sperm cells. Once they are matured, they are released through the rete testis and go through the epididymis where they reach their final maturation and are released through the vas deferens. Before ejaculation, the mature sperm are mixed with secretions from the seminal vesicles, prostate and bulbourethral glands which provide nutrients for the sperm to flourish. We will have a closer look at this hormonal axis in a separate post.
The complexity of both the female and male reproductive system is clear and the intricacies are shown. So the answer to "what came first", I am sorry to disappoint, is that there is no way of knowing but it also doesn't matter as long as both sperm and egg are functioning optimally. Both are essential for embryo development and contribute greatly to fertility of a couple.
