It's in these capillary beds,

它们在毛细血管床上
which are illustrated here by these little meshes,

在图上用这些小孔表示出来
where you have the smallest diameter vessels.

这些血管的直径最小
They're feeding very particular regions of tissue,

它们滋养着组织中特定的部分
not your whole intestine

不是你的整个肠道
but only a very small region of the intestine.

而只是肠道中一片很小的区域
They have thin walls that lack muscle;

毛细血管壁很薄不含肌肉
they're not muscular walls.

它们没有肌肉壁
It's in these capillary beds that exchange of nutrients takes place.

养料在这些毛细血管床上进行交换
It's in these capillary beds that exchange of

在这些毛细血管床上交换的东西有
oxygen, carbon dioxide, sugar, amino acids--

氧气二氧化碳糖氨基酸
that takes place in capillaries.

养分交换在毛细血管中发生