Page 31 - The Miracle of Human Creation

A PERFECT ARMY SET ON ITS GOAL

On the right, we see the system of small ducts that
compose the testes (seminiferous tubules). These
small ducts contain the primary sperm cells which
will later produce the sperm. In the picture above,
we see a detail of the lobule of the testis.

es. For sperm production they have almost 1000 small tubes with a total
length of approximately 500 meters. These small tubes are called the "semini-
ferous tubules". Each one of them is about 50 cm. long and contains the pri-
mary sperm cells that eventually produce the sperm. 2
Seminiferous tubules are lined with sperm-forming cells (spermatogo-
nia) in various stages of development. Later, these cells begin to multiply,
first by undergoing mitosis and then twice undergoing meiosis. As we exp-
lained in the last section, before fertilisation, the primary sperm cell under-
goes 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 spheri-
cal cells containing 23 chromosomes, to be able to perform their fertilising

function, they must go through further changes.
Agroup 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 sper-
matid cells at precisely the right time. Within two or three weeks after me-
iosis has occurred, every spermatid cell will be physically transformed by

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