I work with RNA-seq data and have found a few deferentially expressed genes across particular tissue sample. Now I have been instructed to work with GTEX data to see the deferentially expressed genes across different tissue samples.

Now to go green with GTEX data set, I first don't understand their sample codes like

GTEX-N7MS-0007-SM-2D7W1 for which tissue?

I tried to search the bar codes for GTEX but haven't found any. Please can anyone give some idea for decoding the GTEX bar codes and also performing such analysis. I am sorry if this question is silly because I am a complete naive in the field of NGS.
In [the download section][1], where it says "A de-identified, open access version of the sample annotations available in dbGaP.", you should find a file called `GTEx_Data_V4_Annotations_SampleAttributesDS.txt`, containing the annotation of each sample. For example GTEX-N7MS-0007-SM-2D7W1 is from Whole Blood.

 [1]: http://www.gtexportal.org/home/datasets2