<p>I'm studying for SAT II Bio, and I'm confused about oogenesis; Kaplan doesn't make it very clear. It states that "at birth, all the eggs that a female will ovulate during her lifetime are already present in the ovaries, but these eggs develop and ovulate at a rate of one every 28 days." Since oogenesis is the process of egg/ovum formation, doesn't that imply that oogenesis only takes place at birth?</p>
<p>Would someone care to explain? Thanks!</p>
<p>That says that the first meiotic division takes place in the ovary...hmmm.</p>
<p>From the looks of that diagram, it seems like that the ovarian cells are already existing, but not developed. The cell later splits into a useless polar body and an oocyte. But if oogenesis is ONLY the process of formation, then it takes place only before birth. Doesn't oogenesis also encompass development of the egg, though?</p>
<p>However, the polar body/oocyte splitting stuff is part of meiosis and not oogenesis....argh, this is getting me confused too.</p>
<p>I think they mean that oogenesis = when it does develop and ovulates. </p>
<p>I thought the theory that females don't produce new eggs after birth was proven false?</p>
<p>Oogenesis (detailed):</p>
<p>Primordial germ cell in lining of ovary --> differentiation to oogonium --> replication (stops replicating after birth) --> differentiation to primary oocyte, which is stuck in prophase I of meiosis, once a month, the female ovulates, follicle grows around one egg and that egg is ovulated into the oviduct when LH levels (released by anterior pituitary) soar, causing the follicle to ovulate it. The follicle becomes the corpeus lanteum (something like that) and releases estrogen and progesterone, inhibitiing menstruation, but later deteriorates if egg is not fertilized. As the egg is released, it completes meiosis I, polar body is released, and is stuck at metaphase of meiosis II as a secondary oocyte. When the sperm cell membrane contacts the second oocyte's, the oocyte finishes meiosis, a polar body is released. </p>
<p>The sperm and egg's nucleus disintegrate and a spindle fiber forms, arranging 1 copy of each gamete's chromosomes into 2 daughter cells. So the egg is only an ovum for like a couple of seconds, when the sperm fuses with it's membrane, and the two gamete's nuclei don't actually fuse until after the zygote is divided into 2 daughter cells. (In humans)</p>
<p>Zantedeschia, isn't that ovulation? All the definitions of oogenesis that I found described it as the process of egg/ovum formation.</p>
<p>Anyone else?? HELP!!!</p>
<p>Thats the process by with oogenesis occurs. For an oogonium to become an ovum, it must go through those steps.</p>
<p>Thanks, il bandito</p>
