In a whorl, some of the ridges make a turn through at least one circuit. Whorls are seen in about 25-35 % of fingerprint patterns encountered. The ulna is on the same side as the little finger and the flow of the pattern in a ulnar loop runs in the direction of the ulna (toward the little finger). Ulnar loops are named after the ulna, a bone in the forearm. Radial loops are not very common and most of the time radial loops will be found on the index fingers. The flow of the pattern in radial loops runs in the direction of the radius (toward the thumb). Radial loops are named after the radius, a bone in the forearm that joins the hand on the same side as the thumb. Each loop pattern has is one delta and one core and has a ridge count.
One or more of the ridges enters on either side of the impression, re-curves, touches or crosses the line running from the delta to the core and terminates on or in the direction of the side where the ridge or ridges entered. Loops occur in about 60-70 % of fingerprint patterns encountered. 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. Tented arches have an angle, an up thrust, or two of the three basic characteristics of the loop. On ulnar arches, the ridges slope towards the little finger, have one delta and no re-curving ridges. The ridges of radial arches slope towards the thumb, have one delta and no re-curving ridges. 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. There are four types of arch patterns: plain arches, radial arches, ulnar arches and tented arches.
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. The ridges run from one side to the other of the pattern, making no backward turn. There are three main fingerprint patterns:Īrches are found in about 5% of fingerprint patterns encountered.