Arches are found in about 5% of fingerprint patterns encountered. The ridges run from one side to the other of the pattern, making no backward turn. Ordinarily, there is no delta in an arch pattern but where there a delta, no re-curving ridge must intervene between the core and delta points.
There are four types of arch patterns: plain arches, radial arches, ulnar arches and tented arches.
Plain arches have an even flow of ridges from one side to the other of the pattern, no “significant up thrusts” and the ridges enter on one side of the impression, and flow out the other with a rise or wave in the center.
The ridges of radial arches slope towards the thumb, have one delta and no re-curving ridges. On ulnar arches, the ridges slope towards the little finger, have one delta and no re-curving ridges.
Tented arches have an angle, an up thrust, or two of the three basic characteristics of the loop. They don’t have the same "easy" flow that plain arches do and particularly have “significant up thrusts” in the ridges near the middle that arrange themselves on both sides of a spine or axis towards which the adjoining ridges converge and appear to form tents.
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