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The apico-caudal axis gives various subdivisions by addition of intermediate parts:
for example, tripartition: head, thorax, abdomen.

In fact, one observes even a subdivision very detailed in the form of what is called  "metameres" or "somites", kinds of varied rings, but preserving the same plan.

It is what we can see on a very elementary level either in worms or in human embryo.
These gathered metameres, makes it possible to find the apico-caudal or tripartite structure that was mentioned earlier.