Sanskrit "hrd" and "hanu"

From: Andrew Jarrette
Message: 49461
Date: 2007-08-04

Does anyone know the reason why Sanskrit has <h-> in <hrd> "heart" (also <ha:rdi>) where non-Indo-Iranian languages all have evidence of *k^-?  I think also Avestan has <z-> in this word too.
Similarly, why does <hanu> "jaw" have <h-> where non-Indo-Iranian IE all show *g^-?  I remember the theory that <dva:r> "door" has <d-> instead of <dh-> by the influence of <dva:> "two" (because doors often come in pairs, double-doors), but what could be the explanation for <hanu> and <hrd>?
 
Andrew