DC 2007-04-11, In The Womb 子宫日记 5

21'00- 26'11
8 weeks - 9 weeks -

After growing for eight weeks, the embryo looks more like a tiny human and becomes known as a fetus which in Latin means offspring. She has reached an important milestone. Until now the embryo has been dependent on the nutrients she could extract from her yolk sac, a floating balloon connected to the base of the umbilical cord. A human yolk sac is used briefly and then it vanishes. It is believed that for the first few weeks, it generates nutrients and blood cells for the tiny embryo.

yolk sac: 卵黄囊，一种附在胚胎上的薄膜囊，在硬骨鱼、鲨、爬行动物、鸟类和原始哺乳动物内以卵黄的形式提供早期营养物，在内部循环开始之前，作为人类胚胎的循环系统

umbilical cord: 脐带，在胎儿的肚脐部分和胎盘相连并含有两条脐动脉和一条脐静脉的有弹性的带状结构。脐静脉的作用是输送养料并运走废料

By two months, the yolk sac becomes redundant and shrivels away. The crucial job of feeding and nurturing the fetus is completely taken over by the placenta (胎盘), which is embedded into the wall of the uterus at the end of the umbilical cord. It provides nutrients while filtering out waste. The placenta is the fetus's life support system during her time in the womb. It's a network of very fine blood vessels, reaching into the wall of the uterus. Like the roots of a tree sucking nutrients from the soil, it extracts everything the fetus needs from the mother's bloodstream, food, oxygen, water, and it filters it before passing it into the fetus's bloodstream. Blood, enriched by the mother's diet, travels through the umbilical cord into the fetal arteries.

slab n.（名词） A broad, flat, thick piece, as of cake, stone, or cheese. 厚片：宽、平、厚的一片，如蛋糕、石头或奶酪
(... and passes it into the fetus' blood. )

Everything the fetus doesn't need or the waste products are siphoned out by the placenta and passed back into the mother's bloodstream.

The placenta also filters out many harmful substances that may be in the mother's bloodstream and could damage the fetus. But it can't stop everything and the mother has to be careful with things like prescription drugs, alcohol and nicotine which will pass directly to the fetus.

Some pregnant mothers have an instinctive reaction to avoid food or drink that could be harmful to the fetus. They may be revolted by the smell of alcohol or seafood, meat or mushrooms. The mother's body is effectively controlling her intake of food, telling her what to avoid and instigating cravings to ensure her child gets what it needs.

The first trimester can be an uncomfortable time for the mother. Apart from its nurturing role, the placenta also controls pregnancy by producing hormones, and early on these hormones are what give some women morning sickness. One of these, progesterone, is secreted throughout the term and prevents the mother from releasing more eggs. Others stop the mother's immune system from rejecting the unfamiliar growth inside her.

morning sickness: 孕妇晨吐，在早晨起床时的恶心、呕吐，尤指妊娠早期
progesterone n. 黄体荷尔蒙，黄体酮：类固醇荷尔蒙，化学式为C21H 30O 2，由卵巢的黄体和胎盘分泌，其活动准备子宫移植受精卵子，保持受孕，以及促进乳腺的增大

Another week passes and the nervous system is developing fast, spreading connections throughout the body. Over the course of nine months, the nervous system generates an average of two and a half million neurons every minute. The fetus has been still so far, but now at about nine weeks, her whole body starts to twitch. Movement plays a crucial role in stimulating the growth of muscles and strengthening of joints.

At this stage, the nerves may only extend from the muscles of the leg, for example, back to the spinal cord. The connection to the brain is still growing. So the brain isn't controlling the fetus's movements yet. They are still involuntary reflex spasms. The heart isn't controlled by the brain yet, either. It marches to its own beat and it's been gaining (=pick up 获得) speed since its first twitch to life in the third week.

spinal cord: 脊髓，从延髓开始沿脊柱延伸的粘稠、白色、索状的神经组织，由脊髓开始脊椎神经分叉伸向身体各个部位

spasms: A sudden, involuntary contraction of a muscle or group of muscles, 痉挛

words and phrases:
shrivel: To become or make much less or smaller; dwindle.
siphoned : To draw off or convey through or as if through a siphon.用虹吸管吸出.
instigate: To urge on; goad.
craving: A consuming desire; a yearning.
twitch: A sudden involuntary or spasmodic muscular movement