Is the upper palate really a part of the Maxilla?

I have a underbite , and my midface is really long and there is something off when i close my mouth. My face simply dont look normal. I used to Breath with my mouth since i am 10 , but since 5 month ago , ive start to close my mouth and breath trough my nose and it definitily change the shape of my face , nose bones and my cheeck came foward , its just my upper palate that didnt change , seems back and not in the right position. I thought that the maxilla and the upper palate were all togheter ?

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