Spike,<div>sperm is produced by germ cell that are (from wiki)<br><dl style="margin-top:0.2em;margin-bottom:0.5em;font-family:sans-serif;font-size:13px;line-height:19px;background-color:rgb(255,255,255)"><dt style="font-weight:bold;margin-bottom:0.1em">
Within the <a href="http://en.wikipedia.org/wiki/Seminiferous_tubules" title="Seminiferous tubules" class="mw-redirect" style="text-decoration:none;color:rgb(11,0,128);background-image:none;background-repeat:initial initial">seminiferous tubules</a></dt>
</dl><ul style="line-height:19px;list-style-type:square;margin:0.3em 0px 0px 1.6em;padding:0px;font-family:sans-serif;font-size:13px;background-color:rgb(255,255,255)"><li style="margin-bottom:0.1em">Here, <a href="http://en.wikipedia.org/wiki/Germ_cells" title="Germ cells" class="mw-redirect" style="text-decoration:none;color:rgb(11,0,128);background-image:none;background-repeat:initial initial">germ cells</a> develop into <a href="http://en.wikipedia.org/wiki/Spermatogonia" title="Spermatogonia" class="mw-redirect" style="text-decoration:none;color:rgb(11,0,128);background-image:none;background-repeat:initial initial">spermatogonia</a>, <a href="http://en.wikipedia.org/wiki/Spermatocytes" title="Spermatocytes" class="mw-redirect" style="text-decoration:none;color:rgb(11,0,128);background-image:none;background-repeat:initial initial">spermatocytes</a>, <a href="http://en.wikipedia.org/wiki/Spermatids" title="Spermatids" class="mw-redirect" style="text-decoration:none;color:rgb(11,0,128);background-image:none;background-repeat:initial initial">spermatids</a> and <a href="http://en.wikipedia.org/wiki/Spermatozoon" title="Spermatozoon" style="text-decoration:none;color:rgb(11,0,128);background-image:none;background-repeat:initial initial">spermatozoon</a> through the process of spermatogenesis. The gametes contain DNA for fertilization of an ovum<sup id="cite_ref-5" class="reference" style="line-height:1em"><a href="http://en.wikipedia.org/wiki/Testicle#cite_note-5" style="text-decoration:none;color:rgb(11,0,128);background-image:none;white-space:nowrap;background-repeat:initial initial">[6]</a></sup></li>
</ul><ul style="line-height:19px;list-style-type:square;margin:0.3em 0px 0px 1.6em;padding:0px;font-family:sans-serif;font-size:13px;background-color:rgb(255,255,255)"><li style="margin-bottom:0.1em"><a href="http://en.wikipedia.org/wiki/Sertoli_cells" title="Sertoli cells" class="mw-redirect" style="text-decoration:none;color:rgb(11,0,128);background-image:none;background-repeat:initial initial">Sertoli cells</a> - the true epithelium of the seminiferous epithelium, critical for the support of germ cell development into spermatozoa. Sertoli cells secrete <a href="http://en.wikipedia.org/wiki/Inhibin" title="Inhibin" class="mw-redirect" style="text-decoration:none;color:rgb(11,0,128);background-image:none;background-repeat:initial initial">inhibin</a>.<sup id="cite_ref-6" class="reference" style="line-height:1em"><a href="http://en.wikipedia.org/wiki/Testicle#cite_note-6" style="text-decoration:none;color:rgb(11,0,128);background-image:none;white-space:nowrap;background-repeat:initial initial">[7]</a></sup></li>
</ul><ul style="line-height:19px;list-style-type:square;margin:0.3em 0px 0px 1.6em;padding:0px;font-family:sans-serif;font-size:13px;background-color:rgb(255,255,255)"><li style="margin-bottom:0.1em">Peritubular <a href="http://en.wikipedia.org/wiki/Myoid_cells" title="Myoid cells" class="mw-redirect" style="text-decoration:none;color:rgb(11,0,128);background-image:none;background-repeat:initial initial">myoid cells</a> surround the seminiferous tubules.<sup id="cite_ref-7" class="reference" style="line-height:1em"><a href="http://en.wikipedia.org/wiki/Testicle#cite_note-7" style="text-decoration:none;color:rgb(11,0,128);background-image:none;white-space:nowrap;background-repeat:initial initial">[8]</a></sup></li>
</ul><div><font face="sans-serif"><span style="line-height:19px"><br></span></font></div><div><font face="sans-serif"><span style="line-height:19px">Giovanni</span></font></div><div><font face="sans-serif"><span style="line-height:19px"><br>
</span></font></div><br><div class="gmail_quote">On Fri, Jun 22, 2012 at 2:11 PM, Adrian Tymes <span dir="ltr"><<a href="mailto:atymes@gmail.com" target="_blank">atymes@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On Fri, Jun 22, 2012 at 9:12 AM, spike <<a href="mailto:spike66@att.net">spike66@att.net</a>> wrote:<br>
> 2. The stem cells get to the damage site by some means.<br>
><br>
> 3. It must be they are carried there by the blood.<br>
<br>
</div>Unless they are already present, but if they are always present<br>
near any part of the body, then they are also present near and<br>
probably in the blood too.<br>
<div class="im"><br>
> 4. So there must be stem cells in the blood stream always. So far so<br>
> good?<br>
<br>
</div>Not necessarily. Stem cells could be released upon event, such as<br>
a signal that part of the body is damaged. (Unless they are always<br>
present anyway, per above.)<br>
<div class="im"><br>
> 6. Like any other cell, sperm must come from stem cells.<br>
><br>
> 7. I would assume one particular stem cell becomes one particular<br>
> sperm cell.<br>
><br>
> 8. The stem cells must get to the testes from the bloodstream.<br>
<br>
</div>I think, but I am not sure, that the testes has its own internal stem cell<br>
supply. They divide, and some of them become sperm while others<br>
divide (some of those becoming sperm, and so on). No bloodstream<br>
necessary...<br>
<div class="im"><br>
> 12. Some fraction of these would make their way to the testes, and create<br>
> sperm cells with the donor’s DNA.<br>
<br>
</div>...which breaks this.<br>
<br>
I know this is not the case for a woman's egg cells, all of which are<br>
present when the girl is born.<br>
<br>
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</blockquote></div><br></div>