Dental Problem
A dental cavity (蛀牙) is a hole in a tooth.
A cavity is caused by bacteria (细菌) in the mouth.
Brushing your teeth frequently and regularly can help prevent cavities.
A cracked tooth (隐裂牙) can be caused by biting down on something hard.
Dentists treat a cracked tooth by covering it with a crown (牙冠，齿冠).
A dental x-ray is a picture of your teeth and gums (牙龈).
An x-ray shows what can't be seen on the surface of the teeth and gums.
Braces (牙套) are used by dentists to straighten teeth over a period of years.
Though braces are usually for children, they can also be used for adults with crooked teeth (歪牙，不整齐的牙齿).
To extract a tooth (拔牙), means to remove it from the mouth.
Dentists have to pull hard to extract a tooth.
Exercise:
1.— What happens when a tooth has to be removed from the mouth?
— Dentists have to pull hard to extract a tooth.
2.— What can happen if you bite on something too hard?
— A cracked tooth can be caused by biting down on something hard.
3.— How can dentists get a good view of your teeth and gums?
— A dental x-ray is a picture of your teeth and gums.
4.— What treatment usually take several years to complete?
— Braces are used by dentists to straighten teeth over a period of years.
5.— What is a hole in a tooth?
— A dental cavity is a hole in a tooth.
6. Brushing your teeth frequently and regularly can help prevent cavities.
7. A cracked tooth can be caused by biting down on something hard.
8. Braces are used on people with crooked teeth or after an injury.
Repeat & Read Sentences:
1. A dental x-ray is a picture of your teeth and gums.
2. To extract a tooth, means to remove it from the mouth.
3. Brushing your teeth frequently and regularly can help prevent cavities.
4. Dentists treat a cracked tooth by covering it with a crown.
Internal Organs
The heart pumps blood to all parts of the body through a system of arteries and veins (动脉和静脉).
It's located in the chest, between the lungs, and it beats about once per second.
The kidneys (肾脏) remove waste and toxins (毒素) from the blood.
They are bean-shaped organs and are about 10cm long and 6cm wide.
The lungs exchange oxygen from the air with carbon dioxide from the blood.
They expand (展开，张开) when inhaling (吸气) air, and contract (收缩) when exhaling (呼气) air.
The stomach is below the heart, and it's part of the digestive system.
It uses acids (酸) to digest food before passing it to the small intestine (肠).
The bladder (膀胱) is a balloon-shaped organ that collects urine (尿) from the kidneys.
In an adult, the bladder can hold about half a liter (公升) of urine.
Exercise:
1.— What is located in the chest, between the lungs and above the stomach?
— It's located in the chest, between the lungs, and it beats about once per second.
2.— What is below the heart and connects the small intestine?
— The stomach is below the heart and connects the small intestine.
3.— What organs are used for breathing?
— The lungs are used for breathing.
4.— What are bean-shaped organs and are about 10cm long and 6cm wide?
— The kidneys are bean-shaped organs and are about 10cm long and 6cm wide.
5.— What can hold about half a liter of urine?
— In an adult, the bladder can hold about half a liter of urine.
6. The heart pumps blood to all parts of the body through a system of arteries and veins.
7. The bladder is a balloon-shaped organ that collects urine from the kidneys.
Repeat & Read Sentences:
1. The kidneys remove waste and toxins from the blood.
2. In an adult, the bladder can hold about half a liter of urine.
3. The heart pumps blood to all parts of the body through a system of arteries and veins.
4. The stomach is below the heart, and it's part of the digestive system.
