Development of Fingerprint
Fingerprint ridges are formed during the third to fourth month of foetal development and their formation completed by the sixth months The ridges, thus, formed during the foetal period do not change their course or alignment throughout the life of an individual, until destroyed by decomposition of skin, after death.
ANATOMY OF FINGER SKIN
The skin consists of two main layers: the outer skin or epidermis, and the inner or true skin, known the dermis. The epidermis is constantly being worn away and replaced by new skin generated by the upper layer of the dermis - a papillary layer (stratum mucous) which is the source of the ridges known as 'papillary ridges'. The sweat glands, located in the dermis, discharge sweat at the skin surface through sweat pores found at the top of the ridges.
These are characterized by a slight elevation in the ridges which enter on one side of the fingerprint pattern and exit on the opposite side. The arches are of two subtypes- Plain Arch and Tented Arch. In this no delta formation occurs.
In the plain arch that there is no delta and no significant core. Because there is no delta this pattern, by default, has to be an arch. If you study the image and look at the overall pattern you notice that the pattern area tends to just flow through the print with no significant changes. This makes it a plain arch pattern.
The tented arch pattern consists of at least one up thrusting ridge, which tends to bisect superior ridges at right angles, more or less. The tented arch does make a significant change and does not have the same "easy" flow that the plain arch does. The technical definition is that a tented arch has a "significant up thrust" where a plain arch does not.
Loops constitute between 60 and 70 per cent of the patterns encountered. In a loop pattern, one or more of the ridges enters on either side of the impression, recurves, touches or crosses the line of the glass running from the delta to the core, and terminates or tends to terminate on or in the direction of the side where the ridge or ridges entered. There is one delta. On the right you will see a loop pattern. You will notice that it has one delta (shown in the blue box) and a core (shown in the red box). By definition the existence of a core and one delta makes this pattern a loop. Loops are classified not only by the fact that they have one delta and one core but also by something called a ridge count. Loops are two kinds, 'radial' and 'ulnar', named after the radius and ulna, the two bones in the forearm. The radius joins the hand on the same side as the thumb, and the ulna on the same side as the little finger.
In order to distinguish between ulnar and radial loops you must: 1) Know from which hand the loop pattern comes from and; 2) place your hand palm side down over top of the impression and determine if the recurving ridges originate from the little finger side or the thumb side. If the ridges flow in from the little finger side this would be an 'ulnar' loop.
If the ridges flow in from the thumb side this would be a 'radial' loop. Now, if you were to place your right hand up to the screen and make the same comparison you would find that the pattern area now tends to come in and go out towards your thumb. It so happens that the radial bone in your arm is on your thumb side so now this loop would be considered a radial loop
The whorl pattern consists of one or more free recurving ridges and two points of delta. When the line of the fingerprint disc is placed on the two points of delta, it will bisect at least one of the ridges belonging to the core group. Between 25 and 35 per cent of the patterns encountered consist of whorls. In a whorl, some of the ridges make a turn through at least one circuit. Any fingerprint pattern which contains 2 or more delta's will be a whorl pattern. In the scheme of classification you can make the assumption that if a pattern contains no delta's then it is an arch, if it contains one (and only one) delta it will be a loop and if it contains 2 or more it will always be a whorl.
The technical definition of a plain whorl is a whorl which consists of one or more ridges which make or tend to make a complete circuit, with two deltas’, between which an imaginary line is drawn and at least one recurving ridge within the inner pattern area is cut or touched.