Questions & Answers about Таз підтримує хребет.
Because the basic word order here is subject + verb + object:
- таз = subject
- підтримує = verb
- хребет = object
So the sentence is understood as The pelvis supports the spine.
This matters especially because both таз and хребет are masculine singular inanimate nouns, and in this sentence their forms do not clearly show the difference by themselves. Word order does a lot of the work here.
Хребет is in the accusative case because it is the direct object of the verb.
But for many masculine inanimate nouns in Ukrainian, the accusative singular looks exactly the same as the nominative singular. So:
- nominative: хребет
- accusative: хребет
That is why the form does not change.