问题 单项选择题

成熟红细胞更替时间是()

A.100d

B.120d

C.80d

D.60d

E.30d

答案

参考答案:B

解析:

红细胞是血液中数量最多的有形成分,起源于骨髓造血干细胞。在红细胞生成素作用下,经红系祖细胞阶段,分化为原红细胞,经数次有丝分裂发育为早幼、中幼和晚幼红细胞。晚幼红细胞通过脱核成为网织红细胞,这一过程在骨髓中进行,约需72h。网织红细胞经约48h成完全成熟的红细胞,释放入血液,平均寿命约120d,衰老红细胞主要在脾破坏,分解为铁、珠蛋白和胆红素。

阅读理解

阅读理解。

     Like most people, you've probably never given your blood glucose (糖) a second thought, unless you have

diabetes (糖尿病). But researchers now know that whether or not you have diabetes, eating too much can

make your blood glucose go up and down and can increase the danger of heart disease. It may be even bad for

your memory.

     This realization has greatly changed the way we understand food and health. Luckily, none of these things

happen ovemight, and even small changes in the food you eat every day can start you on a healthier path.

     When you are hungry, do you reach for a chocolate cake or a box of biscuits? These "fast-acting" foods

are handy and they take no time at all to dissolve (溶化) in your stomach. Then they race into your blood,

running through your body with blood glucose. The trouble is the comfort doesn't last long, leaving you feeling

hungry again. As a result, your blood glucose will run out of control.

     It's no wonder most of us have less energy than we'd like and feel tired too often. It's also no wonder that

most of us weigh more than we want to. Yes, eating too much and exercising too liLtle are main reasons, and

ever changing blood glucose will send you shopping for bigger jeans.

     For most of us even when our blood glucose goes up and down after a large meal, our body can bring it

back to normal in a few hours. Only people with untreated diabetes have blood glucose levels that stay quite

high most of the time.

     For a long time, doctors thought that only these people needed to take care of their blood glucose levels.

Now, we know that even in healthy people, high levels after meals can damage (损坏) the body, even if it

never causes diabetes.

1. How does our blood glucose change after a large meal?

A. It remains unchanged.

B. It stays on high levels.

C. It goes up and down.

D. It comes back to normal.

2. What does the writer think of "fast-acting" foods?

A. He thinks they are delicious.

B. He thinks they are easy to get.

C. He thinks they make us healthy.

D. He thinks they damage our body. 

3. What shall we do if we want to keep the normal blood glucose?

A. Check our blood glucose after each meal.

B. Have proper food and exercise every day.

C. Eat certain kind of medicine before meals.

D. Ask the doctor for help from time to time.

选择题