Difference between Cambria Math italic font in Word 2010

In Microsoft Word you can use Equation Editor to insert math equations. The font used in the editor is shown as Cambria Math. I found there is a difference between italic version of the font in the editor and those out of the editor, as shown in the following picture (The first row is the alphabets in the editor and the second row is those out of the editor:

However the normal version (non-italic) of the font shows no difference:

I what to know what's the cause for the difference. Thanks.

In response Matthew Strawbridge's answer:
I checked my font folder and there is only Cambria Math Regular there. There are 4 versions for the Cambria font though. So I make a new observation. In the image below from top to bottom there are: Cambria, Cambria Italic, Cambria Math Italic in Equation Editor, Cambria Math, Cambria Math Italic.

It seems the alphabet font in Cambria and Cambra Math are the same. Since Cambra Math doesn't have a italic version, so there is a sloped Roman one. However what makes me confused is that the third row (Cambria Math Italic in Equation Editor) doesn't look like any other row, so I really wonder which font is used instead.

Edit: According to this blog post from Microsoft's Murray Sargent, the italic characters shown in the Equation Editor are the special mathematical italics that exist as a separate range of glyphs.

The Cambria Math font is a Roman font, but appears to have these mathematical italic glyphs within it. Therefore the mathematical variables will look different from the sloped Roman you get when typing the same thing in Word and making it italic.

Getting the same glyphs in running text is possible, but tricky. For example, you can get a Mathematical italic small r you can type 1d45f and press Alt+X to convert the Unicode code to the corresponding character.