请教一句正确的句子的结构

云游

Taste buds are onion-shaped structures with between 50 and 100 taste cells, each of which has finger like projections poking through the opening, called the taste pore, located at the top of the taste bud.

这里是一个正确的句子，想请教下：
1. each of which在词句子中的结构和成分
2. "called..."和"located..."此两处的结构在在这里是并列的修饰成分吗？他们的修饰对象又是什么呢？
谢谢！

云游

http://forum.chasedream.com/thread-535336-2-1.html

wyw1018

each of which是一个定语从句
called 和located 都是修饰the opening的，只不过called相当于一个插入语，去掉called就是下面的形式：
each of which has finger like projections poking through the opening located at the top of the taste bud