Author Archives: krwalter

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….

http://www.mothers35plus.co.uk/plac_rec2.htm#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 (http://health.howstuffworks.com/sexual-health/sexuality/human-reproduction10.htm) 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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