How were the initial values for the chaining variables in MD5 determined?

The original description of the MD5 algorithm initializes the values of A, B, C, and D to the following:

word A: 01 23 45 67
word B: 89 ab cd ef
word C: fe dc ba 98
word D: 76 54 32 10


How were the values determined and does it matter how they were chosen?