Here are pictures which show how blood vessels branch from the body side to feed the frenulum and inner skin etc.
Cutting out piece and clamping it back / sewing in some adult cases alters the blood flow - ie damage.

Warning graphic picture of intact below:


Click image for larger version

Name:	tumblr_oepigqHFyW1vhkwfjo5_1280.jpg
Views:	124
Size:	300.8 KB
ID:	10033