What is a Vein?
什么是静脉
What is a vein? First thing you need to know is that there are three main types of vessels that transport nutrients through the body – the arteries, the veins, and the capillaries.
什么是静脉？首先需要知道的是，我们有三种主要的血管通过身体运输营养物质，它们是动脉、静脉和毛细血管。
The image on the screen shows you some of the most important veins in your body which are all these blue structures. Here is one of the most well-known, the inferior vena cava.
屏幕上的图像描绘了身体中的一些最重要的静脉，它们都是蓝色的结构。这是最为人所知的静脉之一，下腔静脉。
Veins carry blood away from the tissues and towards the heart and have thin walls.
静脉将血液从组织输送到心脏，血管壁很薄。
Their internal lumen is larger than that of the arteries due to the fact that they contain blood under low pressure. They also have valves that prevent the blood from flowing backwards.
它们的内腔比动脉的内腔大，因为它们在低压下含有血液。它们也有防止血液回流的瓣膜。
Blood that returns to the heart via the veins comes from the capillaries. They are the point where the arteries and veins merge with one another and serve as a complex plexus of many tiny branches.
通过静脉返回心脏的血液来自毛细血管。它们是动脉和静脉相互汇合处，是由许多细小分支组成的复杂血管丛。
This is also where the exchange of gases, nutrients and waste products takes place because the capillary walls are thin and fenestrated.
这也是气体、营养物质和废物交换发生的位置，因为毛细管壁很薄且有孔。
After they are emptied of oxygen and nutrients, the capillaries collect into venules, and finally into the veins which wind their way back to the heart.
当氧气和营养物耗尽后，毛细血管聚集成小静脉，最后汇入静脉，然后回流到心脏。
（图源：太帅图库）
相关单词学习
Capillary
①发音和释义
cap•il•lar•y/kəˈpɪləri/n. 毛细血管
One of the tiny, hairlike blood vessels between the arteries and the veins.
单词 capillary 由下列成分构成
capill 毛发，毛细管
+
-ary（后缀）与…有关
（图源：太帅图库）
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