Hi Classmates!  Personally, in the past I didn't think discussion boards helped me learn and I thought of them as more of busy work than a learning tool. However, after hearing what Dr. Wilson and Paris said made me want to give DB an honest try and hopefully get more out of it. And what better time to try it, than this week! 

I, like a lot of us in class, am a visual learner so maybe we can include visual aids in this DB that helped each other with this concept. 

Let's all challenge each others thoughts and hopefully teach each other more about conception and the first trimester. 

To start off the DB, the corpus luteum plays an important role in implantation as it secrets progesterone for the uterus to prepare for implantation (decidualization). However, the rising levels of estrogen also plays a role in the initial growth of the endometrium. If there was no progesterone there wouldn't be a thick endometrium for the egg to burrow in. Another hormone that is related to implantation is human chorionic gonadotropin (hcG) that is released when the blastocyst embeds in the endometrium.  The hcG helps the growth of the corpus luteum which then produces progesterone, making sure the uterus is nice and plump for the blastocyst.  I would say the progesterone is the most important hormone out of all of them even though they all work together and conception couldn't happen without the other. If we didn't have progesterone then the functional layer would shed causing menstration and make it difficult for the egg to implant. 

https://www.youtube.com/watch?v=kWHAzsYec6o

Hormones play a very important role in early pregnancy. My initial reaction is that no one hormone is more important than the other in this process, because if even one thing is wrong/missing, the pregnancy likely won't be successful.

The first one that pops into my head when discussing implantation is progesterone -- promote gestation! This is secreted by the corpus luteum in the ovary after ovulation. By secreting progesterone, the corpus luteum is ensuring we have a nice plump pillow for the blastocyst to land in when it reaches the uterus. Estrogen also helps with endometrial thickening, although we see higher estrogen levels prior to ovulation as that is what the developing Graafian follicle is secreting. We will see more estrogen from the placenta, but that occurs after implantation.

The other big pregnancy hormone is hCG (human chorionic gonadotropin). Big surprise, it comes from the chorion, specifically the trophoblast cells. hCG helps extend the life of the corpus luteum, which means more progesterone for a better endometrial burrow for the embryo.

If you remove either of these from the equation, you won't get the endometrium you need to catch and maintain the blastocyst/embryo.

When most people think of pregnancy, chances are their first thought is not about hormones, but more so the miracle of life. I think of hormones as the base of all things pregnancy related. They are what set the stage for what is to come over the next 9 months, so it is important to understand how they function and interact with one another. Before we can become anything more than a twinkle in our parents' eye we must lay down the groundwork. In gynecology, we learned the importance of the hypothalamus secreting GnRH to act on the anterior pituitary to eventually release LH and FSH, which will trigger the ovaries to release a few hormones of its own, estrogen and progesterone. Prior to implantation we must have ovulation, fertilization, cleavage, and blastulation which essentially means our hormones will be put to work. During implantation we rely on the syncytiotrophoblast to release the pregnancy hormone hCG. This is critical as it will prompt the corpus luteum to continue secreting progesterone to keep the endometrium thickened and prevent both the functional layer and blastocyst from being sloughed off. It's similar to a game of telephone, if the syncytiotrophoblast doesn't get the right message to the corpus luteum the pregnancy is lost and in this case so is the game! And last but not least we have estrogen, which helps ready the endometrium along the women's menstrual cycle so it may be thick enough if fertilization is to occur. I don't believe any hormone is more important over another as they seem to rely on each other. Hormones are essentially small pieces that when put together create an amazing puzzle! If anyone has any information on what is happening hormonally during the cleavage process, please share, I didn't find any credible information in my research!

Hormones are the key factors that contribute to a woman's ability not only conceive but also to carry the pregnancy to term. As you can see from the graph below (the 2 right columns) LH, FHS and Estrogen are prominent in the follicular phase of a woman's cycle. They stimulate follicle growth and release of the follicle into the fallopian tube. After ovulation progesterone is secreted from the Corpus Luteum which tells the uterine lining to thicken (aka creates the best home) for the incoming blastocyst. Once the blastocyst implants itself into the uterine lining the trophoblast cells release the hormone HCG into the mother's system. That HCG communicates back to the Corpus Luteum that fertilization has occurred and that the uterine lining needs to stay thickened. Thus, progesterone production increases and the decidualization process of the endometrial tissue should begin to support the embryo.

In my opinion I believe all hormones involved are very important. For example, If in the follicular phase of a woman's cycle there is too much of one or more hormones or not enough she may not even have a mature follicle to release an ovum. Therefore, fertilization does not occur. Conversely, let's say the first half of the cycle goes smoothly and the ovum is fertilized but the woman's progesterone response is poor then the blastocyst that has formed now doesn't have the ideal lining to attach to and therefore may result in failed implantation. Lastly, we can say everything goes smoothly in the beginning, ovulation occurs, the ovum is fertilized, the uterine lining is thick and 5- 10 days later implants into the uterus however does not secrete HCG. The corpus luteum would not get the signal that there is a pregnancy, progesterone levels would eventually decrease the lining would shed and the blastocyst would not have the proper environment to prosper.

Hormones are the driving factor before, during, and after a pregnancy. They work together as a synchronous team to ensure that the body can support an embryo, and that the embryo will develop correctly. When follicles are developing in the ovary they begin secreting estrogen. When estrogen levels are high, this signals for luteinizing hormone (LH) to be secreted from the anterior pituitary gland. The LH surge is responsible for ovulation. Skipping forward in a woman's cycle to post ovulation, the ruptured follicle is now a corpus luteum and begins to secrete progesterone. Progesterone is extremely important in developing and maintaining the endometrium, otherwise known as decidualization. This hormone allows the endometrium to grow thick and provide a good environment for the blastocyst.

Once the blastocyst loses its zona pellucida and begins to implant into the endometrium, the trophoblast cells start secreting human chorionic gonadotropin. This hormone maintains the corpus luteum so it can continue to secrete progesterone until the placenta can take over. Human chorionic gonadotropin is also the hormone that is measured to determine if a woman is pregnant. 

While there are several hormones that are needed during a pregnancy, I believe that progesterone is the most important one. Without this hormone the endometrium will not grow to be nice and thick and instead the low levels will cause menstruation to begin and the endometrium to be sloughed off. This can be a tragic event because the blastocyst will either not be able to implant, or it may implant but the low levels may cause the lining to shed, therefore causing a spontaneous abortion.

The most important hormones at work during implantation and cleavage are estrogen, progesterone, and human chorionic gonadotropin (HCG). Initially, estrogen causes the pituitary gland to release luteinizing hormone, triggering a single ovarian follicle to to release an egg (ovum). This ruptured follicle is now considered a corpus luteum, and secretes progesterone. At ovulation, estrogen initially thickens the endometrium, preparing it for a possible zygote. Once the egg is released, progesterone maintains endometrial thickness throughout the pregnancy and the functional layer of the endometrium is not shed if a zygote successfully implants. HCG, produced by trophoblast cells, extends the life of the corpus luteum so that it continues to secrete progesterone. 

I cannot find information on the hormones related to cleavage, but that the sperm activates the divisions to begin about 24-30 hours after fertilization. I would love to hopefully understand more of what drives the divisions to begin!

I don't believe one can say firmly which hormone is most important to a pregnancy. They all work together to prepare the endometrium to carry a pregnancy for 9 months. Without estrogen, the endometrium would never get to the point it needs to be for progesterone to take over, and without HCG, progesterone would fall back down, causing the functional endometrium to slough and lose the pregnancy.

Howdy everyone,

As a side note: The first hormones that lead to cleavage and implantation are GNRH, LH, and FSH! It's important to not lose sight of where we begin.

Once the egg is released and the follicle turns into the CL, the CL begins making progesterone and some estrogen. Progesterone causes the decidualization reaction (which further prepares the endometrium for implantation) while the conceptus is going through cleavage. Without this progesterone implantation would likely not lead to a successful IUP, and the functional layer of the endometrium would sluff off.

Next, the blastocyst implants into the endometrium and the trophoblast cells begin making hCG => hCG keeps the CL alive until the placenta is able to make its own progesterone. No hCG=no CL=no progesterone=no live IUP.

It's hard to say that one hormone is more important than another because they are all required for a full term pregnancy; however, progesterone (really it's GNRH*) alone is the most important hormone for implantation to occur.

This video is from Crash Course! It's an excellent overview of pregnancy. (They have ton of videos on all sorts of topics.)

https://www.youtube.com/watch?v=BtsSbZ85yiQ

Sarah

Hormones play a HUGE role in a successful implantation and cleavage process. If even just one hormone isn't producing properly it could cause demise of the pregnancy as a whole. In my opinion all of the hormones are equally important and all have a domino affect on each other. For example, hCG which is a hormone that detects pregnancy, is produced by the placenta after implantation and supports the function of the corpus luteum, which then leads to the corpus luteum producing key hormones such as progesterone that is a major support to the baby's livelihood until the placenta takes over around 8-12 weeks. Therefore, as I mentioned each hormone plays a very important role in implantation and the cleavage process. Before taking this class, I honestly didn't realize all that went into the implantation process or the significance of these hormones. These hormones also are a help to us as sonographers when reviewing lab values. If we see an unusual lab value of any specific hormone that we know if detrimental to this process, it should automatically raise a red flag for us when performing our exam to be even more cognizant and thorough. Below I attached a link which a breakdown of six key hormones in pregnancy that was very helpful for me to read. Hopefully, you lovely ladies will appreciate it as well.

https://www.compoundchem.com/2019/02/28/pregnancy-hormones/

I believe there isn’t necessarily one single hormone that is more important, because they all play an important role and work together to make implantation possible.  Starting in the hypothalamus, secretion of GnRH occurs, then the anterior pituitary gland releases LH and FSH, and the ovaries produce estrogen and progesterone. LH surge triggers ovulation. The Graafian follicle is now a corpus luteum and secretes progesterone which causes the endometrium to thicken and prepare for implantation. After implantation, hcG is released, which keeps the corpus luteum alive, allowing it to keep secreting progesterone to maintain the endometrium. hCg also plays an important role in determining if a woman if pregnant, because levels can be detected.

Here’s a short animation video of implantation of a blastocyst. It’s fascinating to know how each hormone plays a role in allowing this important process to occur!

https://www.youtube.com/watch?v=PAVo16b_6j4

I found this small chart to be a good summary!

Hormones play huge role in or daily lives so you can imagine how important they are when carrying another human being inside you. It all starts off with Gnrh, LH, and FSH, a surge of LH initiates ovulation. After the mature follicle ruptures, releasing the egg, it becomes the corpus luteum. This structure is really important because it secretes progesterone. Progesterone keeps the endometrium nice and thick for the blastocyst to attach to and survive. Trophoblasts produce HCG which plays a big role in pregnancy because it's main function is to keep the corpus luteum functioning and we're able to detect pregnancy with these levels. I liked this graph because it shows the hormone levels throughout the whole pregnancy and it's easy to follow.  I also saw some graphs with hPl (human Placental Lactogen) and I don't remember going over it. Does anyone know about it and what's the purpose? In my opinion, I don't think one hormone is more important over another, they are all needed for specific things and without one the others wouldn't perform the same.

The hormones are a significant part during the implantation and cleavage process. Hormones are needed to stimulate and grow important parts of the uterus to set implantation. Once fertilization occurs, the sperm and egg become one—the zygote. This zygote performs cleavage, the rapid division of cells. As this is multiplying and developing, there is a rise of high level of hormones called estrogen. Estrogen would thicken the endometrium. The corpus luteum, would then produce the hormone, progesterone. Progesterone allows implantation to occur. If these two hormones were to decrease, menstruation would begin again. Although, if the hormones steadily increase, then we have a successful road to implantation.

About six days after fertilization, implantation would then occur. The syncytiotrophoblast begins to produce the hormone hCG. This hormone ultimately extends the life of the corpus luteum! As the corpus luteum also continuously produces progesterone to prevent the endometrium from shedding.

Personally, I do not believe any type of hormone is more important than another. They all spontaneously work together to build and create a healthy environment for life to grow. Below is a shared image that displays the stages of zygote to cleavage to implantation.

Sounds silly to ask... but if estrogen and progesterone must increase for pregnancy to occur, would pathology occur if there was more of estrogen than progesterone? Or vice versa? Or it wouldn't even affect this process?

The cleavage process lasts from the first division of the zygote and ends when the conceptus becomes a blastocyst. This corresponds to day 1 to day 5 or 6 following fertilization. Once the blastocyst is hatched from the zona pellucida, the implantation process can begin. 

According to the image below, during the 5-6 days following ovulation estradiol levels drop then rise again. Additionally, the progesterone levels begin rising significantly around 1-2 days after ovulation. During the implantation window (starting ~ 6 days after), the progesterone level is rising to its peak. Perhaps during the first 1-2 days it takes for progesterone levels to take off, estradiol plays a role in continuing to grow the endometrium to give a solid foundation for decidualization to build on top. 

Progesterone is responsible for driving the decidualization reaction in the endometrium. Decidualization makes a number of changes in the morphology of the tissue to make it more receptive to implantation.  Therefore, in order for implantation to be successful, progesterone levels have to stay elevated. If the progesterone levels drop prior to implantation, the spiral arteries of the functional endometrium will start to constrict. The endometrium will no longer be in a state to accept the blastocyst and allow it to thrive. 

Once the implantation process begins, hCG is secreted by trophoblasts of the blastocyst. hCG’s job is to keep the corpus luteum from regressing in order to maintain the elevated progesterone levels until the placenta can take over toward the end of the first trimester. 

If we are thinking only about what the hormones do specifically in the cleavage and implantation processes, I would consider progesterone to  be more important because without decidualized tissue, a pregnancy would likely not be feasible. However, thinking about the bigger picture of the entire cycle, estradiol plays a larger role. Without the rise in estradiol levels, there would be less endometrial thickening, no LH surge, no ovulation, no corpus luteum, and no chance for fertilization. 

Image credit: https://courses.lumenlearning.com/wm-biology2/chapter/the-ovarian-cycle-the-menstrual-cycle-and-menopause/

Image source: https://media.springernature.com/original/springer-static/image/chp%3A10.1007%2F978-4-431-55972-6_2/MediaObjects/332562_1_En_2_Fig2_HTML.gif

There are a few hormones that play a significant role in the implantation and cleavage process. In order for implantation to occur, there needs to be an egg to implant. Ovulation, releasing of an ovum from a mature follicle, is trigger by luteinizing hormone (LH). The mature follicle the egg was released from, transforms into the corpus luteum. The corpus luteum secretes progesterone, which thickens the lining of the uterus and prepares it for implantation. Furthermore in order for cleavage to occur, a zygote must be present to divide. In other words, a sperm needs to have successfully fused membranes with the ovum. According to Khan Academy, estrogen plays a key role in assisting the sperm to pass through the vagina and cervix to reach the uterus to create a zygote. Estrogen secretes glycogen that is metabolized to make the vagina acidic. Low pH levels discourage the growth of pathogens, which can prevent sperm cells from reaching the ovum. Semen, the fluid that contains sperm, has basic properties that allow it to thrive in the acidic conditons. Furthermore estrogen thins the cervical mucus, providing for a smoother transport of sperm (khanacademy.org). However once fertilization occurs, a mucus plug seals the cervix, which creates a barrier that protect the fetus from infection. Lastly the syncytiotrophoblast cells of the blastocyst secrete hCG, indicating pregnancy.

         In my opinion, all the hormones are equal because they each play a role to contribute to development of fetus.

https://www.khanacademy.org/test-prep/mcat/cells/embryology/a/egg-meets-sperm

All hormones in implantation and the cleavage process play a huge role in a woman's reproductive journey. GnRH is secreted by the hypothalamus and stimulates FSH and LH from the anterior pituitary gland. FSH is responsible for promoting follicle development within the ovary leading to an egg being produced. Estrogen appears around the egg which is needed in order for a pregnancy to be supported. Estrogen stimulates the endometrium to thicken before ovulation occurs. There is then a surge in LH which triggers ovulation. LH is responsible for the maturation of a graafian follicle, which contains the matured ovum. The follicle then becomes the corpus luteum, which produces estrogen and large amounts of progesterone. Progesterone causes the endometrium to become thickened (decidualization occurs) and prepared for a blastocyst to implant successfully. Once implantation begins, trophoblasts produce HCG which plays an important role in maintaining the corpus luteum. Without the HCG being maintained, the pregnancy would not be able to continue on because the blastocyst would not be well supported. HCG needs to remain maintained until the placenta later on within the first trimester takes over the process of maintaining progesterone.

It seems as if all of the hormones play such a crucial role in the development and maintenance of a fetus especially estrogen and progesterone. Without estrogen, we wouldn’t have the endometrial thickening prior to ovulation occurring, an LH surge would not take place, which would lead to the absence of a graafian follicle being matured, and finally the corpus luteum wouldn’t be there to maintain a pregnancy. For progesterone, if we didn’t have it around then we wouldn’t have decidualization reaction to occur and implantation would not be possible.

I also wanted to share this vide on Khan academy which makes embryogenesis a bit easier to digest. I like the visuals within it: 

Early embryogenesis - Cleavage, blastulation, gastrulation, and neurulation (video) | Khan Academy

While I want to say that progesterone is the most important because it prepares the uterus for implantation (decidualization) and without it, a pregnancy would not occur, one must also keep in mind the other hormones that got the zygote to the point of implantation in the first place. Without LH, there would have been no egg released to fertilize and then go through the cleavage process. Without hCG to sustain the corpus luteum there would be a shortage of progesterone. The female body is a well orchestrated chaos of hormones that work in tandem to ensure that everything functions the way it should.

Here is a diagram that I think is really helpful! Kinda huge, sorry.

Hormones play a key role during the implantation process. Without the corpus luteum secreting progesterone and estrogen then we would  not have nice thick bed for the blastocyst to implant itself into it. Also, hCG comes in to maintain the corpus luteum so that these hormones can continue to be secreted. Therefore, I think that all the hormones are equally as important because the have to work together as a team.

As I was going through the discussion board and I was looking at videos I see variations in the amount of cells that make up the morula. Is it 16 or 32? Or is it a range from 16-32?