Oogenesis (Nursing)

00:02 So when were talking about gamete formation in the female, this is referred to as oogenesis.

00:10 Oogenesis is the production of female gametes.

00:14 This can take years to complete and begins in the fetal period.

00:21 Starting with the oogonia, which are diploid ovarian stem cells.

00:27 These are going to multiply many times by way of mitosis and also store nutrients.

00:34 From there, we will develop primary oocytes and a primordial follicle that will become surrounded by follicular cells or follicle cells.

00:47 During fetal development, the primary oocytes will begin meiosis, but they will stall and that first step of prophase 1.

00:58 It is presumed that at birth, females contain most of the primary oocytes that they will have in their lifetime.

01:09 So after puberty begins, each month a few primary oocytes are going to become activated.

01:17 One of these activated primary oocytes will become the dominant follicle that will resume meiosis 1.

01:26 Recall, it's been arrested in prophase 1 since fetal development.

01:33 After puberty, the division of meiosis 1 is going to be completed and we get two haploid cells of different sizes.

01:43 The first is going to be the larger secondary oocyte which is going to contain almost all of the mothers cell cytoplasm and organelles.

01:54 The second is going to be a smaller polar body or the first polar body.

02:00 This is going to be a very small cell that is pretty much devoid of any cytoplasm at all.

02:07 This will sometimes later degenerate or it may divide and then degenerate after it divides.

02:16 The second oocyte is going to arrest in metaphase 2 and becomes the ovulated ovum.

02:25 If the ovum is not penetrated by sperm it will then deteriorate.

02:31 However, if fertilization occurs and it is penetrated by the sperm, the secondary oocyte will complete meiosis 2 yielding a functional gametes or an ovum and as well a second polar body.

02:48 Again, this polar body will eventually disintegrate.

02:54 So if we compare oogenesis which occurs in the females to spermatogenesis which occurs in the male we find that the number of functional gametes that are produced in each differ.

03:08 In oogenesis, we only produce one viable ovum and three polar bodies.

03:17 This is due to unequal divisions, which ensure that the oocyte is going to have ample nutrients for the six to seven day journey that it must take from the ovaries to the uterus.

03:31 The polar bodies are the smaller cells that are formed will degenerate and die.

03:38 This is an opposition to spermatogenesis where we produce for viable sperm.

03:47 Along with a difference in the functional gametes that are produced, there's also differences in error rates.

03:54 Spermatogenesis has an error rate of about three to four percent, but in oogenesis, the error rate is much higher at 20%.