Objective 77: Recognize that a blastocyst secretes human gonadotrophin, which prolongs the life of the corpus luetum
When I read this objective, I really believed that it was going to be a no brainer and I could just breeze right through it. But boy, was I wrong! There is a lot more to the menstrual cycle that I previously believed there to be. I honestly don't give my body enough credit, even though I'm pretty sure that all of us women would rather not have to deal with this very precious "gift" mother nature decides to give us. The textbook gave alot of great information regarding this topic, but there was way more information than I could comprehend. I never knew there was so much work when it came to our periods each month! The lecture outlines did a great job in summarizing the follicular, ovulatory, and luteal phases of the menstrual cycle. There is a chart in chapter 26 page 920, that really did reinforce the information, but it was kind of hard to take a clear picture of the chart so instead I borrowed them from our chapter 26 lecture outline. These charts inform you about the fluctuation of gonadotrophin levels, the ovarian cycle, the fluctuation of ovarian hormone levels, and a summary of the three phases of the uterine cycle. Wow, there is so much going on here!
Along with this helpful information from our textbook, I still was having a difficult time understanding all of the steps involved within the menstural cycle. The speaker is a little mono-tone I think, but he summarizes the information on the phases of the menstural cycle and also shows where on the charts the cycle is occuring. He actually breaks the cycle into 4 phases which was a little different then what the book said, but either way this video was helpful in reinforcing what I heard in lecture and read from the book. The video sums up the menstrual cycle perfectly when it states that it is "a complicated hormonal phenomenon". I wouldn't disagree with that logic!
I believe that objective 77 fits very nicely with the menstural cycle, because if fertilization occurs then the blastocyst implants and the corpus luetum prepares for pregnancy. But let's back up here a bit. Human Gonadotrophin is very important in prolonging the lifespan of the corpus luetum. If fertilization occurs, the implanted blastocyst secretes human gonadotrophin, which then effects the corpus luetum. The corpus luetum then secretes estrogen and progesterone until the placenta develps. If fertilization does not occur, the corpus luetum degenerates and the uterine lining sloughs off. The book doesn't do a good job of explaining this whole process to me, but this picture here gives me a little more insight.
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