如图是肾的内部结构部分放大示意图，请填空．
（1）肾是形成______的器官．每个肾包括大约100万个结构和功能单位，叫做______．
（2）从成分上分析，与入球小动脉相比较，肾静脉中所含的______相对较少．
（1）泌尿系统由肾脏、输尿管、膀胱、 * * 组成，其中肾脏是形成尿的器官，输尿管、膀胱、 * * 是输送尿的管道，肾单位是肾脏的结构和功能的基本单位，每个肾包括大约100万个肾单位．
（2）当血液流经肾小球时，除了血细胞和大分子的蛋白质外，血浆中的一部分水、无机盐、葡萄糖和尿素等物质，都可以经过肾小球滤过到肾小囊内，形成原尿；当原尿流经肾小管时，其中对人体有用的物质，包括大部分水、全部葡萄糖和部分无机盐，被肾小管重新吸收，并且进入包绕在肾小管外面的毛细血管中，重新回到血液里；原尿中剩下的其他废物，如尿素、一部分水和无机盐等由肾小管流出，形成尿液．所以，从成分上分析，与入球小动脉相比较，肾静脉中所含的尿素相对较少．
故答案为：（1）尿液（或尿） 肾单位 （2）尿素
Choose the words or expressions and complete the passage Exam time is the most stressful (最有压力的) period of the year. You’ve worked all the term on your classes and now it’s the time to prove what you have learned. With so much at stake, it is easy to get stressed about your exams. However, with the right amount or hard work and focus you can pass your tests 1! When I was in school, I used to get very stressed over my examinations. So did my friends. Some people stopped eating and others ate too much! Some 2 and others burned themselves out! The most important thing to remember when studying is not to panic! Take the middle path---stay calm, eat healthy food and get your rest. Stressing out and _3___yourself too hard is just as dangerous as not studying enough. A tired, overworked brain is just as useless as a stupid, empty one! So, what do you do? Set aside a time each day for study and a time For __4 . You may have less time to relax than usual, but you still need to let your brain rest for a few moments. Get plenty of sleep. If you are_ 5 , information will not stick in your memory. Finally, eat healthy food that fuels your body and mind. It does no good to look at your exams like the rest of your life 6 them. Instead, just view them as another obstacle (障碍物) you will overcome. You have overcome all kinds of obstacles in your life so far. With the right amount of work and focus, you will pass your examinations with flying colors! High school is right around the corner.
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