On the other side of the smooth muscle layer is the serosa.

在平滑肌层的另一边是浆膜层。

Next is the muscularis externa, a smooth muscle layer, which contracts automatically, without you even having to think about it.

往内是肌层，由平滑肌构成；它们不需要你的意志参与，便能够自主收缩。

Also, between the circular and the longitudinal muscle layer, there's a plexus, or networks of nerves, which help coordinate muscle contraction and relaxation.

另外，在内环肌和外纵肌之间，还有神经丛（神经网络）的分布；神经丛可以协调肠道平滑肌的收缩与舒张。

Okay, so the intestinal wall, like this one, has lots of ridges and grooves, and also can be separated into the mucosal layer, submucosal layer, muscle layer, and serosa.

好，那肠壁有很多的脊和槽，像这个图片一样，肠壁还可以被分成黏膜层、黏膜下层、肌层和浆膜层。

Remember that those plexuses are in the muscle layer or submucosal layer, so a normal biopsy with just the mucosa wouldn't cut it, you need a sample of submucosa to see if the submucosal plexus is there or not, right?

记住！神经丛存在于肌层或黏膜下层，因此普通黏膜活检无法取到，需要黏膜下层的标本来检查是否有黏膜下层神经丛。