Dental Problems
牙齿的问题
A dental cavity is a hole in the tooth.牙洞是牙齿上的一个洞。
A cavity is caused by bacteria in the mouth.口腔是由口腔中的细菌引起的。
Brushing your teethfrequently and regularly canhelp preventcavities.频繁的且有规律的刷牙有助于预防蛀牙。
A crackedtooth can be caused by biting down on something hard.牙齿破裂可能是咬硬东西造成的。
Dentists treat a cracked tooth by covering it with a crown.牙医用牙冠覆盖裂开的牙齿来治疗（临床）。
A dental X-ray is a picture of your teeth and gums.牙齿x光片是你牙齿和牙龈的照片。
An x-ray shows what can't be seen on the surface of the teeth and gums.x光片显示牙齿和牙龈表面看不到的东西。
Braces are used by dentists to straighten teeth over a period of years.牙套被牙医使用矫正牙齿已经很多年。
Though braces are usually for children, they can also be used for adults with crooked teeth.虽然牙套通常是给孩子用的，他们（牙套）也可以给牙齿歪的成年人使用。
To extract a tooth, means to remove it from the mouth.拔除牙齿，就是把牙齿从嘴里拔出来
Dentists have to pull hard to extract a tooth.牙医必须使劲拔牙
Dentists often inject something into the gum to block the pain during the extraction process.牙医经常在拔牙的过程中往牙龈里注射一些东西来止痛
Braces are used on people with crooked teeth or after an injury.牙套用于牙齿弯曲或受伤后的人。
Internal Organs内部器官
The heart pumps blood to all parts of the body through a system of arteries and veins.心脏通过动脉和静脉系统将血液输送到身体的各个部位。
It's located in the chest, between the lungs, and beats about once per second.它位于胸腔，在两肺之间，大约每秒跳动一次。
The kidneys remove waste and toxins from the blood.肾脏排出血液中的废物和毒素。
They are bean shaped organs and are about 10 centimeters long and 6 centimeters wide.它们是豆形的器官（脏器），长约10厘米，宽约6厘米。
The lungs exchange oxygen from the air with carbon dioxide from the blood.肺把空气中的氧气和血液中的二氧化碳交换。
They expand when inhaling air, and contract when exhaling air.它们吸入空气时膨胀，呼出空气时收缩。
The stomach is below the heart, and it's part of the digestive system.胃在心脏下面，它是消化系统的一部分。
It usesacidstodigestfood beforepassingit to the small intestine.在食物进入小肠之前，它利用酸来消化食物。
The bladder is a balloon shaped organ that collects urine from the kidneys.膀胱是一个气球状的器官，从肾脏收集尿液。
In an adult, the bladder can hold about half a liter of urine.成年人的膀胱可以容纳大约半升的尿液。
