FERTILIZATION 2 - Fertilization Traditional Fertilization:...

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Fertilization Traditional Fertilization: Sperm + Oocyte In Vitro Fertilization: Intercytoplasmic sperm injection Oogenesis (Making eggs) Begins in the fetal ovaries where stem cells (oogonia) produce primary oocytes About 2 million of these primary oocytes hang about in the ovary at birth Primary oocytes are diploid (i.e. they have full set of 46 chromosomes) At the onset of puberty (about 11 or so), only 300,000 primary oocytes are left in the ovaries. This is a significant loss from the initial count of 2,000,000. At menopause, 0 primary oocytes are left in the ovaries! The decline of primary oocytes cannot be explained only by ovulation (You would have to ovulate 500,000+ times!) The path to developing haploid oocytes The primary oocytes are held in prophase of meiosis I unchanged from the way they were produced in the fetus (via oogonia). At the start of the menstrual cycle, meiosis restarts and the primary oocytes become secondary oocytes. Many primary oocytes turn into secondary oocytes. Despite many eggs developing at the same time, only one will be ovulated per menstrual cycle. The completion of meiosis II beings exactly at the time when the sperm contacts the egg (fertilization). The development of eggs in every cycle is called the ovarian cycle and there are two phases to the cycle. Follicular Phase: Egg and surrounding cells (the follicle) develop up to the point of ovulation Many oocytes will enter the follicular phase, only a few will develop up until they can be called the mature follicle. Luteal phase: Leftover bits of the follicle hang around and secrete hormones (particularly progesterone) to prepare the lining of the uterus (the endometrium) for a fertilized egg. Components of a follicle The inner portion of a follicle is called the Oocyte. The outer portion of a follicle is called the Granulosa.
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Only one mature follicle per menstrual cycle Once the follicle has been ejected, the component that is left over (granulosa layer) will become the corpus Luteum. Occurs right after the follicular phase Can only be 14 days. Does not change. Ovulated Secondary Oocyte Characteristics Zona pellucida: Protein coat sitting outside the egg. Acts as protection. Nucleus Stuck in meiosis II:
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This note was uploaded on 01/16/2012 for the course KINESIOLOG 1Y03/1YY3 taught by Professor Parises during the Spring '11 term at McMaster University.

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FERTILIZATION 2 - Fertilization Traditional Fertilization:...

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