May 5, 2011- Reproduction

Hey everyone! Just as a reminder, the last homework assignment is due on Wednesday. There will also be two review sessions this week.

The first question that came up in lecture was why do people eat placentas.

The placenta is the organ that connects the fetus to the uterine wall. It allows for nutrient uptake, gas exchange and waste elimination. There are actually many rituals and customs regarding the placenta once the baby has been born. Interesting examples include naming the placenta or hanging it from a tree for scavengers to eat. Placentas are often ceremoniously buried to symbolize the relationship between humans and the earth. Placenta is also used in many beauty products because it is a pure source of protein.

(I like how they mention the cucumber. . .)

The practice of eating the placenta is called placentophagy. It is actually very common amongst mammals because it is a very good source of nutrition. Humans usually have adequate diets so do not need to eat placenta for this purpose.  It is believed that eating the placenta will prevent post partum depression and possibly encourage milk production in new mothers. The placenta contains high levels of prostaglandin, which shrinks the uterus. The placenta also contains iron and small amounts of oxytocin, which can the decrease the stress of childbirth and stimulate milk production. Placenta is eaten by men as well, although it is dangerous to eat another person’s placenta because of illnesses transmitted through blood (HIV, Hepatitis, etc).

Here is a video. Enjoy!

Caution: does show footage of a placenta and a cooked placenta

And if you fancy making yourself a plate of placenta spaghetti or perhaps a nice cocktail….

The next question was what happens if two sperm penetrate an egg at the same time. This occurs in less than 1% of fertilizations.

So as we learned in lecture today, fertilization occurs in the fallopian tubes. There are two fallopian tubes, but only one contains an egg. According to an article on discovery health only 1000 sperm actually reach the fallopian tubes. And then they must make a choice…. two roads diverged in uterus. . . lol. According to the article I found ( half of the sperm go to the wrong fallopian tube, which I thought was interesting.

A molar pregnancy can occur if two sperm fertilize the same egg. It’s estimated that 1/1,500 pregnancies in the U.S. are molar pregnancies. A complete molar pregnancy happens when there are two sets of chromosomes from the father and none from the mother. The fertilized egg develops into a growth called a mole. There is no embryo, amniotic sac, or normal placenta. Most partial molar pregnancies occur when there are two sets of chromosomes from the father and one set from the mother, so there are 69 total chromosomes instead of 46. This can occur when chromosomes from the sperm are replicated or if two sperm fertilize an egg.

Women with molar pregnancies might have normal symptoms of pregnancy at the beginning. Later in the molar pregnancy they might experience heavy spotting and bleeding or abdominal cramping. Some women develop preeclampsia. However, an ultrasound can usually diagnose a molar pregnancy long before these conditions develop.

Semi-identical twins are also a result of two sperm fusing with a single egg, before becoming two embryos.  The embryos usually do not survive. There is only one known case of semi-identical twins. The twins were born in the US in 2007. They have identical genes from their mother, but share only half the genes from their father. One of the twins is male, but the other is a hermaphrodite (has both ovarian and testicular tissue). The most likely explanation is that two sperm cells – one with an X chromosome and one with a Y chromosome – fertilized the same egg, which later split into two embryos.



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7 responses to “May 5, 2011- Reproduction

  1. cgalimanis

    Wow great blog! I especially liked the placenta pill footage! Definitely left me with chills 🙂
    I think that it is really interesting that sperm actually choose which fallopian tube they will travel and that most choose the wrong tube! I do wonder what happens to those sperm that chose the eggless fallopian tube. Are they still “active” for a while or do they die off pretty quickly?
    The concept of molar pregnancy is also interesting. Would the woman have to give birth to the “mole”, simular to a late term miscarrage, once it is determined that it is not a fetus or is it just reabsorbed by the body?

  2. krwalter

    I would imagine that their survival rate is the same as the sperm that choose the correct fallopian tube. Mole pregnancies are pretty weird. I was gonna post a picture. If you’re interested you should look it up. It basically forms a bunch of cysts within the uterus. I think it is very uncommon for these pregnancies to proceed to full term, just because it can be detected very easily. But there are some pics on the internet that show a baby.

  3. jwestmore

    This is the first blog post in which I have replied. All I have to say is… GROSS. Gross, Gross, Gross.

  4. drewgriffiths70

    I still can’t get over the fact that you can eat a placenta. .. Also I was wondering, how is it possible to have two sperm reaching the egg, when the egg depolarizes the membrane? Does the two sperm have to get to the egg at the exact same time, or does the process for depolarizing take awhile?

  5. Lauren

    It is quite interesting to learn that people actually do eat placentas. I always thought it was a cultural thing, but I had never seen proof of such acts. It’s quite disgusting, but I guess to those certain cultures, it’s quite a delicacy. Having watched my dog give birth to 12 puppies, and eating EVERY placenta that comes out with each puppy, I was quite grossed out! I guess it’s a delicacy for dogs too!

  6. I think the part about semi-identical twins is fascinating!! Its almost as if they are the only people in the world that share 75% of their genes. Its also amazing that they survived. The article I read said that most cases of one egg being fertilized by two sperm result in an inviable embryo. And to add, they were conceived naturally! I think its also really interesting that one is anatomically male but the other is a hermaphrodite. We talked about how when one sperm penetrates the egg, chemical changes don’t let any other in. I wonder if the second sperm got in right before the chemical changes occured resulting in the twins.
    Here’s some interesting facts on twins:
    -1 in 250 pregnancies can result in identical twins
    -Identical twins share the same DNA, but will have their own fingerprints
    -About 25% of identical twins are called mirror image twins. For example if -one has a mole under her right eye, the other will have it under her left eye.
    -In some African countries such as Nigeria, the rate of twin pregnancies can be as high as 1 in 20
    -Elvis Presley had a twin who did not survive after birth. His name was Jesse Garon
    Great Blog by the way! 🙂

  7. mgranzella

    This blog was awesome! I liked (even though it was gross) the video of the placenta and that picture reminds me too much of a BBQ sandwhich! I think that it is interesting that there are people who will do different things with their placenta!
    Also, I think that it is really intersting how the sperm decide which fallopian tube to travel into. This is just another reason why the human body is amazing!

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