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Apr 03, 2022
5 min read

The basics of our reproductive systems

During our first IVF attempt, we came across a lot of new terminology and information in a very short time, and it was quite challenging to take it all in. We were very familiar with some of the information that was given to us, and slightly less familiar with some of the more technical terms and procedures. By all means, a lot of material was completely new to me, even though I attended biology classes at school, but there may be a slight chance that I did not pay enough attention. Live and learn! There is no shame in having a little refreshment course.

It can be very beneficial to have a better understanding of what is happening in our bodies and reproductive system, so here are some basics that we all should be familiar with. Let’s start with the ladies!

Ovaries: they are small, almond shaped glands, and primary female reproductive organs. They are located on either side of the uterus, at the end of each fallopian tube. The ovaries have three main functions: they produce and store all the eggs a female is born with; they produce female hormones estrogen and progesterone; the ovaries release, usually, one egg during each menstrual cycle for fertilisation.

Follicle: a follicle is a small fluid-filled sac located in the ovaries that contains a developing egg. During each menstrual cycle, several follicles begin the maturation process. However, usually only one of the follicles reaches maturity and becomes dominant. Later on, this follicle is selected to grow until it is ready to release the egg, which is ready for fertilisation.

Egg: also called ovum, is the female reproductive cell. The eggs are located inside of the follicles in the ovaries. Interesting fact is that females are born with all of their eggs that they will have during their lifetime. Their initial number reaches hundreds of thousands, but drops to about 200,000 by adolescence, and continues to decrease with age. The egg is the largest human cell, and measures about 0.1 - 0.2 mm in diameter. During ovulation, the egg leaves the follicle and enters the fallopian tube where it awaits fertilisation.

Fallopian tubes: also called uterine tubes, are two narrow, 10-12 cm long ducts that connect the ovaries to the uterus. They have three main functions: they transport the male sperm cells towards the egg, which is waiting for fertilisation in the tube; they provide suitable environment for the process of fertilisation; they transport the egg from the ovary to the uterus. If the fallopian tubes are blocked, an egg cannot meet the sperm, fertilisation cannot take place and pregnancy will not occur.

Ovulation: when a follicle ruptures, the egg is released from one of the ovaries. It typically happens around day 14 of the menstrual cycle. The eggs have quite a short lifespan and are viable only for 12-24 hours. Sperm remain viable for several days inside of the female reproductive tract, therefore 3 days prior to ovulation and 2 days after ovulation are considered the most fertile days for females. This is also called a fertility window, which is a term used very often in the IVF community. During the actual IVF process, ovulation is regulated by hormones.

Menstrual cycle: it is a series of natural changes in hormone production and the structures of the uterus and ovaries. These hormonal changes make it possible for a pregnancy to occur. There are four phases of the menstrual cycle: menstruation, follicular phase, ovulation and the luteal phase. The average menstrual cycle is 24 to 38 days long, however, some women may experience irregular cycles that last shorter or longer amount of time. The first day of the menstrual cycle is the first day of menstrual bleeding, also called a period, which typically lasts 4 to 8 days.

Now that we have covered the ladies, let’s move on to the men!

Spermatogenesis: it is the process of producing and developing sperm. It is a 74 day long cycle during which germ cells, male reproductive cells, develop into sperm with the ability of independent movement and fertilisation. Male testicles produce several million sperm per day!

Sperm: sperm is the male reproductive cell. Some people may use these two words interchangeably, yet, sperm and semen are two different terms; semen is a fluid, which contains sperm, but it only makes up only 5% of the weight of the semen. Sperm cells are very tiny, measuring only 50 micrometers from head to tail. A sperm can travel about 3 mm per minute, and it is viable and capable of fertilisation for 30-50 hours after ejaculation. However, 90% of the sperm in a man’s ejaculate are deformed; they can be misshaped, have a small or large head, or no tail. Just a small percentage of sperm are actually able to fertilise an egg.

Sperm count: it is a measure of the number of sperm in each ejaculation. A normal sperm count ranges from 15 million to 200 million per millilitre of semen. Low sperm count is considered when there are less than 15 million sperm per millilitre, or less than 39 million sperm per ejaculate. This phenomenon is refer to as oligospermia and it affects one in every six couples. Unfortunately, it has been a very serious issue in many developed countries in the last few decades.

Sperm motility: this refers to the ability of sperm to move forward and progress for at least 25 micrometers per second. A sperm analysis examines how many of the sperm are motile. The higher the number, the better. It has been debated for many years that sperm with Y chromosomes, or the “boy” sperm, can swim faster than sperm with X chromosomes, known as the “girl” sperm. However, it has been proven to be a myth.

Sperm morphology: the semen analysis test examines sperm morphology, which refers to the size, shape and overall appearance of a man’s sperm. The results are shown as a percentage of sperm that appear normal. Sperm are examined in order to evaluate male fertility, because the egg can only be penetrated by sperm that have a “normal” shape. Interestingly enough, this will be a fairly low number since many sperm have an abnormal shape. The good news is that there are millions of them and only one is needed to fertilise the egg.

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