TedTest

From the Ted Talk by TED-Ed: Why do women have periods?

Unscramble the Blue Letters

A handful of species on Earth share a seemingly mysterious trait: a menstrual cycle. We're one of the slecet few. Monkeys, apes, bats, humans, and possibly elephant shrews are the only mammals on Earth that menstruate. We also do it more than any other animal, even though its a waste of nutrients and can be a physical inconvenience. So where's the sense in this uncommon biological process? The answer begins with pregnancy. During this process, the body's resources are cleverly used to sphae a suitable environment for a fetus, creating an internal heavn for a mtheor to nurture her growing child. In this respect, pnacegrny is awe-inspiring, but that's only half the story. The other half reveals that pregnancy places a mother and her child at odds. As for all living creatures, the hamun body evolved to promote the spread of its genes. For the mother, that means she should try to provide eluqaly for all her offspring. But a mother and her fetus don't share exactly the same genes. The ftues ineithrs genes from its father, as well, and those genes can promote their own survival by extracting more than their fair share of resources from the mother. This evolutionary conflict of interests places a woman and her uonbrn clhid in a biological tug-of-war that plays out inside the womb. One factor contributing to this internal tussle is the placenta, the fetal organ that connects to the mother's blood supply and nourishes the fetus while it grows. In most mammals, the placenta is confined behind a barrier of maternal cells. This barrier lets the mother control the supply of nutrients to the fetus. But in humans and a few other species, the ptlacnea actually penetrates right into the mother's circulatory system to directly access her blood stream. Through its placenta, the fetus pumps the mother's aeertris with hormones that keep them open to provide a pnneearmt flow of nutrient-rich blood. A fetus with such unrestricted ascces can manufacture hormones to increase the mother's blood sugar, daitle her arteries, and inflate her blood pressure. Most mammal mothers can expel or reabsorb embryos if rueqierd, but in humans, once the fetus is connected to the blood supply, snrveeig that connection can rsulet in hemorrhage. If the fetus develops poorly or dies, the mother's health is endangered. As it grows, a fetus's ongoing need for reucsoers can cause intsnee fatigue, high boold pressure, and conditions like dietebas and preeclampsia. Because of these risks, pregnancy is always a huge, and sometimes dunaregos, investment. So it makes sense that the body should screen embryos carefully to find out which ones are worth the challenge. This is where msttornuaien fits in. Pregnancy starts with a process called implantation, where the embyro embeds itself in the endometrium that lnies the uterus. The endometrium evevlod to make implantation dificulft so that only the healthy embryos could svruive. But in doing so, it also selected for the most vigorously invasive embryos, creating an eurovaioltny fbadceek loop. The embryo engages in a complex, elsqeiuitxy timed haonrmol dialogue that tsrrfmaons the endometrium to allow implantation. What happens when an embryo fails the test? It might still manage to attach, or even get ptlray through the endometrium. As it slowly dies, it could leave its mother vulnerable to infection, and all the time, it may be entmitig hormonal signals that disrupt her tsseuis. The body avoids this problem by sipmly removing every possible risk. Each time ovulation doesn't result in a healthy pregnancy, the womb gets rid of its endometrial lining, along with any unfertilized eggs, sick, dying, or dead emorybs. That protective process is known as menstruation, leading to the period. This biological triat, bizarre as it may be, sets us on course for the continuation of the human race.

Open Cloze

A handful of species on Earth share a seemingly mysterious trait: a menstrual cycle. We're one of the ______ few. Monkeys, apes, bats, humans, and possibly elephant shrews are the only mammals on Earth that menstruate. We also do it more than any other animal, even though its a waste of nutrients and can be a physical inconvenience. So where's the sense in this uncommon biological process? The answer begins with pregnancy. During this process, the body's resources are cleverly used to _____ a suitable environment for a fetus, creating an internal _____ for a ______ to nurture her growing child. In this respect, _________ is awe-inspiring, but that's only half the story. The other half reveals that pregnancy places a mother and her child at odds. As for all living creatures, the _____ body evolved to promote the spread of its genes. For the mother, that means she should try to provide _______ for all her offspring. But a mother and her fetus don't share exactly the same genes. The _____ ________ genes from its father, as well, and those genes can promote their own survival by extracting more than their fair share of resources from the mother. This evolutionary conflict of interests places a woman and her ______ _____ in a biological tug-of-war that plays out inside the womb. One factor contributing to this internal tussle is the placenta, the fetal organ that connects to the mother's blood supply and nourishes the fetus while it grows. In most mammals, the placenta is confined behind a barrier of maternal cells. This barrier lets the mother control the supply of nutrients to the fetus. But in humans and a few other species, the ________ actually penetrates right into the mother's circulatory system to directly access her blood stream. Through its placenta, the fetus pumps the mother's ________ with hormones that keep them open to provide a _________ flow of nutrient-rich blood. A fetus with such unrestricted ______ can manufacture hormones to increase the mother's blood sugar, ______ her arteries, and inflate her blood pressure. Most mammal mothers can expel or reabsorb embryos if ________, but in humans, once the fetus is connected to the blood supply, ________ that connection can ______ in hemorrhage. If the fetus develops poorly or dies, the mother's health is endangered. As it grows, a fetus's ongoing need for _________ can cause _______ fatigue, high _____ pressure, and conditions like ________ and preeclampsia. Because of these risks, pregnancy is always a huge, and sometimes _________, investment. So it makes sense that the body should screen embryos carefully to find out which ones are worth the challenge. This is where ____________ fits in. Pregnancy starts with a process called implantation, where the ______ embeds itself in the endometrium that _____ the uterus. The endometrium _______ to make implantation _________ so that only the healthy embryos could _______. But in doing so, it also selected for the most vigorously invasive embryos, creating an ____________ ________ loop. The embryo engages in a complex, ___________ timed ________ dialogue that __________ the endometrium to allow implantation. What happens when an embryo fails the test? It might still manage to attach, or even get ______ through the endometrium. As it slowly dies, it could leave its mother vulnerable to infection, and all the time, it may be ________ hormonal signals that disrupt her _______. The body avoids this problem by ______ removing every possible risk. Each time ovulation doesn't result in a healthy pregnancy, the womb gets rid of its endometrial lining, along with any unfertilized eggs, sick, dying, or dead _______. That protective process is known as menstruation, leading to the period. This biological _____, bizarre as it may be, sets us on course for the continuation of the human race.

Solution

haven
transforms
emitting
partly
equally
embryo
tissues
lines
select
simply
mother
intense
difficult
dilate
embryos
diabetes
exquisitely
fetus
placenta
arteries
human
result
unborn
feedback
inherits
dangerous
menstruation
blood
hormonal
pregnancy
severing
access
permanent
evolutionary
required
trait
resources
survive
shape
child
evolved

Original Text

A handful of species on Earth share a seemingly mysterious trait: a menstrual cycle. We're one of the select few. Monkeys, apes, bats, humans, and possibly elephant shrews are the only mammals on Earth that menstruate. We also do it more than any other animal, even though its a waste of nutrients and can be a physical inconvenience. So where's the sense in this uncommon biological process? The answer begins with pregnancy. During this process, the body's resources are cleverly used to shape a suitable environment for a fetus, creating an internal haven for a mother to nurture her growing child. In this respect, pregnancy is awe-inspiring, but that's only half the story. The other half reveals that pregnancy places a mother and her child at odds. As for all living creatures, the human body evolved to promote the spread of its genes. For the mother, that means she should try to provide equally for all her offspring. But a mother and her fetus don't share exactly the same genes. The fetus inherits genes from its father, as well, and those genes can promote their own survival by extracting more than their fair share of resources from the mother. This evolutionary conflict of interests places a woman and her unborn child in a biological tug-of-war that plays out inside the womb. One factor contributing to this internal tussle is the placenta, the fetal organ that connects to the mother's blood supply and nourishes the fetus while it grows. In most mammals, the placenta is confined behind a barrier of maternal cells. This barrier lets the mother control the supply of nutrients to the fetus. But in humans and a few other species, the placenta actually penetrates right into the mother's circulatory system to directly access her blood stream. Through its placenta, the fetus pumps the mother's arteries with hormones that keep them open to provide a permanent flow of nutrient-rich blood. A fetus with such unrestricted access can manufacture hormones to increase the mother's blood sugar, dilate her arteries, and inflate her blood pressure. Most mammal mothers can expel or reabsorb embryos if required, but in humans, once the fetus is connected to the blood supply, severing that connection can result in hemorrhage. If the fetus develops poorly or dies, the mother's health is endangered. As it grows, a fetus's ongoing need for resources can cause intense fatigue, high blood pressure, and conditions like diabetes and preeclampsia. Because of these risks, pregnancy is always a huge, and sometimes dangerous, investment. So it makes sense that the body should screen embryos carefully to find out which ones are worth the challenge. This is where menstruation fits in. Pregnancy starts with a process called implantation, where the embryo embeds itself in the endometrium that lines the uterus. The endometrium evolved to make implantation difficult so that only the healthy embryos could survive. But in doing so, it also selected for the most vigorously invasive embryos, creating an evolutionary feedback loop. The embryo engages in a complex, exquisitely timed hormonal dialogue that transforms the endometrium to allow implantation. What happens when an embryo fails the test? It might still manage to attach, or even get partly through the endometrium. As it slowly dies, it could leave its mother vulnerable to infection, and all the time, it may be emitting hormonal signals that disrupt her tissues. The body avoids this problem by simply removing every possible risk. Each time ovulation doesn't result in a healthy pregnancy, the womb gets rid of its endometrial lining, along with any unfertilized eggs, sick, dying, or dead embryos. That protective process is known as menstruation, leading to the period. This biological trait, bizarre as it may be, sets us on course for the continuation of the human race.

Frequently Occurring Word Combinations

Important Words

access
animal
answer
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arteries
attach
avoids
barrier
bats
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body
called
carefully
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challenge
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fair
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lines
lining
living
loop
mammal
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manage
manufacture
maternal
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menstrual
menstruate
menstruation
monkeys
mother
mothers
mysterious
nourishes
nurture
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partly
penetrates
period
permanent
physical
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pregnancy
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promote
protective
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pumps
race
reabsorb
removing
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reveals
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