病原体是指致病的微生物，我们的身体对其有很多防御的机制。 皮肤是第一道物理屏障，它形成难以渗透的保护层。我们的皮脂腺也会分泌酸性物质，从而防止病原体的生长。 病原体很容易通过口、鼻、眼进入。唾液、粘液和眼泪中含有溶菌酶，能分解许多细菌的细胞壁。 我们的呼吸系统有著自己的防禦系統，从鼻毛,粘液到酶都是。 微生物会进入我们的食物和饮料中，而胃里的盐酸可以杀死很多有害的微生物。 我们的血液也有很好的防御系统，血液中含有血小板和血纤维。血小板和血纤维能使血液凝固结痂，从外部封闭伤口。我们的血液还有一个神奇的武器，那就是白血球。它们可以追捕和消灭病原体。可以吞噬病原体也可以中和病原体毒素对人体的影响。 访问我们的网站：www.fuseschool.org，在这里，我们所有的视频都按主题进行了精心的分类和编排，来了解我们还能提供些什么。评论、点赞并与其他同学分享。你可以提问和回答问题，老师会为你解惑。 这些视频可以采用翻转课堂的模式，也可以作为复习指导。 Twitter: https://twitter.com/fuseSchool
Interest is the amount charged by a lender to a borrower. It means that if you borrow some money from a bank, you have to pay back more than the money you borrowed. Equally, if you have a savings account and deposit some money, the bank will pay you interest as a sort of thank you for saving with th
In this video we are going to look at a few different ways in which plant hormones can be used. Plant growth hormones (auxins) can be used as selective weedkillers. The selective weedkillers contain growth hormones, that cause the weeds to grow really quickly. This means the weed is absorbing nutr
Algebraic fractions are simply fractions with algebraic expressions either on the top, bottom or both. We treat them in the same way as we would numerical fractions. In this video we look at how to simplify algebraic fractions, and how to add and subtract them. VISIT us at www.fuseschool.org, wh
