Re: VRD: How is life imparted to sperm

Dear Robert,

As you may know all living organisms are made of cells. A sperm is a 
living cell but it is a highly specialized type of cell. A sperm cell is 
formed through a complex set of cell divisions, differentiation and 
maturation process called spermatogenesis. Spermatogenesis occurs in an 
organ in the male called the testis. The testis is the only organ in which 
sperm cells are made and reside. You cannot artifically create a sperm 
cell. You can culture mature the body in the laboratory. 

Spermatogenesis begins when a young male hits puberty. Before puberty, the 
immature germ cells called spermatogonia reside in the testes. They 
migrated to the testes during embryonic development and they 
stay "immature" until they received certain hormonal and biochemical 
signals that occur once a young man hits puberty.  The spermatogonia then 
go through a series of divisions in which they are eventually transformed 
into a cell called a spermatozoa. The cells at these different stages are 
called: spermatogonia, spermatocytes and spermatids. The entire process of 
spermatogensis in a human male takes approximately 60 days. 

The spermatids are gradually transformed into mature sperm. This is known 
as spermiogenesis. The mature sperm has a tail which enables them to 
propel themselves.

If you would like to read more about spermatogenesis, I would suggest 
reading, Alberts, B et.al., 1994, "The Molecular Biology of the Cell," 
pp1026-1027 or consult basic biology textbook. If you have more specific 
questions, please feel free to email me.

Elsa Lee