In order to fertilise an egg, about 200-300 million sperm cells are made ready for the journey. This is a surprising number, but there is an important reason for it. As we will see in more detail later, a great number of the sperm that enter the mother-to-be's body die on the way and the number of sperm which are able to reach the egg is very small. Therefore, the great number of sperm obviates the risk of the fertilisation of the egg not being successful. This army of millions of individual sperm is produced in the male reproductive organs called the testes. The sperm go through many stages in their production in the testes and, in order for them to survive, the place where they are produced must be cool. The normal human body temperature is 37oC. This temperature would kill the sperm, therefore sperm cannot live inside the body. One of the most noticeable characteristics of the testes is that they are outside the body. Because of this special design according to which God created the male body, the sperm have a specially prepared place for their production.
The testes are composed of a system of small tubes. This system of tubes occupies quite a large space, which allows millions of sperm to be produced quickly and in a place where they can be easily stored. The reason that sperm must be quickly produced and stored is understandable when we consider that, for an egg to be fertilised, 200-300 million sperm must be produced.
When we think about the number of sperm produced, we can call the testes miniature factories. For sperm production they have almost 1000 small tubes with a total length of approximately 500 meters. These small tubes are called the "seminiferous tubules". Each one of them is about 50 cm. long and contains the primary sperm cells that eventually produce the sperm.3
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Seminiferous tubules are lined with sperm-forming cells (spermatogonia) in various stages of development. Later, these cells begin to multiply, first by undergoing mitosis and then twice undergoing meiosis. As we explained in the last section, before fertilisation, the primary sperm cell undergoes division by meiosis and lowers by half the number of its own chromosomes, so that the baby will receive 23 chromosomes from the father.
At the end of these divisions, four cells called spermatids are formed which as yet have no ability to fertilise an egg. In order for these spherical cells containing 23 chromosomes, to be able to perform their fertilising function, they must go through further changes.
A group of cells has been put in place to respond to this special need of the male reproductive system and to assist the development of the spermatid cells at precisely the right time. Within two or three weeks after meiosis has occurred, every spermatid cell will be physically transformed by these "nurse" cells (Sertoli cells) which surround them. Sertoli cells function to support and nourish the immature sperm cells by giving them nutrient material, hormones, and enzymes that are necessary for causing appropriate changes in the spermatids.4 In the final stage of this process, the qualities proper to a fully developed sperm emerge the tail, the head and the acrosome, that part of the head which is filled with enzymes. (For detailed information see the section entitled "The Sperm Meets the Egg")
All this work of transformation is performed by the Sertoli cells found within the walls of the tubules. These cells have cytoplasmic extensions and are quite large. The Sertoli cells hold the developing spermatid cells firmly in their arms, assuring that they are well injected into their own cytoplasm. In this way, they will provide them with nourishment during their development, and monitor them.5
In this process which we have briefly described, a really great miracle occurs. The sperm which assures the continuation of the human race is brought into being, thanks to Sertoli cells, which are made up of proteins and nucleic acids. Let's think for a moment. The fact that a Sertoli cell, rather a cell without intelligence or consciousness and without eyes, ears or a brain, can devote itself to such a duty is truly a wonder. The fact that such a thing occurs is clear proof that the cell is under the direction of a supreme intelligence. Moreover, that these cells are exactly at the proper place, (that is, in the seminiferous tubules where the sperm develop,) and that they have exactly the requisite qualities (for example, they are larger than the spermatids) is one of the millions of proofs of the perfect design of the human body. God has placed every one of the approximately 100 trillion cells that make up the human body in its proper place; He has given to each one the qualities it needs; and He has given each one the instinct to do its work perfectly. As we are told in the Qur'an;
... There is no creature He does not hold by the forelock. My Lord is on a Straight Path. (Qur'an, 11: 56)