The Critical Stage of Friction Ridge and Pattern Formation

Permanence, individuality

Cellular attachments ensure _____, while variable stresses and cellular distributions account for _____.

Tension, 10.5, 16

Volar patterning is dependent upon the _____ across the surface of the developing skin during a critical stage of approximately __ to __ weeks EGA

The onset of epidermal cellular proliferation and the timing of the regression of the volar pads

Fingerprint ridge counts are predominantly affected by what two combined timing events? 

• Recite the philosophy of identification

• Define the methodology used in examinations

• Explain the scientific bases of the permanence and uniqueness of friction ridge skin based upon empirical and scientific research data

All latent print examiners should understand and be prepared to do to what three things?

1993

Until ____, the standard of admissibility was that the scientific technique or procedure be generally accepted and practiced by the relevant scientific community

Observational

Knowledge of the physical and natural scientific basis, rather than _____ data alone, must be exhibited to explain why friction ridge skin is unique and why this uniqueness is permanent

Anastomoses

Branches of the epidermis that bridge primary and secondary ridges and mold the papillae pegs of the dermis

1. The adherence of the epidermal cells to each other

2. The basal cell layer of the epidermis and its attachment to the basement membrane

3. The attachment of the basement membrane to the dermis

There are three principal structural elements of skin that allow for the permanence of friction ridge detail: 

1.8 mm, keratinocytes

The epidermis of volar skin is approximately _____ in thickness and is comprised mostly of cells called _____.

Differentiation

Keratinocytes undergo a maturation process, termed _____, as they move from the basal layer of the epidermis to the surface.

Stratum germinativum

The basal layer of keratinocytes of the epidermis; the generating layer

Desmosomes, hemidesmosomes

Basal cells are joined to each other by complex cell junctions called _____ and are joined to the basement membrane by another type of junction called a _____.

Stratum spinosum

A zone 2 to 4 cell layers in thickness in which the keratinocytes exhibit the first stage of differentiation by organizing the necessary components of keratin synthesis; the spinous layer

Stratum granulosum

The keratinocytes of this layer are the last of the living cells of the epidermis as they begin to display the first precursors of keratin; as keratinization occurs, all other cellular activities and components degrade, marking the beginning stages of cell death; the granular layer

Stratum lucidum

The small layer of histologically clear cells at the top of the granular layer

100, 25, 30

The horny layer of adult volar skin can be up to __ cells in thickness, making it __ to __ times thicker than most other areas of the body.

30

The entire progression through the different stages of cell maturation, from cell birth to exfoliation, is approximately __ days.

720

Individuals who live to be 60 years old will undergo complete turnovers of epidermis approximately ___ times in their lifetime.

The complex and secure junction between cells of the epidermis

What is the first structural element that enforces the permanence of friction ridges (and other skin features)?

The attachment site between the basal cells of the epidermis and the basement membrane

What is the second structural element of permanence?

True

True or False: The rate at which a basal cell produces new epidermal cells is reasonably consistent.

Fibrous

The _____ material of the dermal matrix gives the skin bulk and tensile strength while allowing for flexibility.

Nonfibrous

The _____ material of the dermal matrix forms a ground substance which influences the passage of nutrients, allows for cellular migration, and provides a continuous medium for structural fibers.

The attachment of the dermis to the basement membrane through small, anchoring fibers

What is the third structural element attributing to permanence?

Structural, filter

The BMZ serves a _____ function and acts as a _____ between the epidermis and dermis.

Increase, more

Dermal papillae (increase/decrease) in number and become arranged in a progressively (more/less) crowded state throughout adulthood

Rate

The consistent proportional _____ of basal cell proliferation explains why third level detail remains permanent during the aging process of skin, in spite of changes in the shape of the epidermal-dermal boundary.

Central nervous, cardiovascular

With respect to fingerprint patterns, one milestone along the pathway from blueprint to model involves the development of the _____ _____ and _____ systems.

Capillary-nerve

Several researchers have postulated that the distribution of the ____-____ pairs at the junction of the epidermis and dermis directly influences the alignment of the primary ridges.

Developmental fields

Groupings of fingers on which patterns have a greater tendency to be similar

Compression

A theory proposes that the same forces of _____ on the deeper layers of the epidermis which condition ridge alignment also stimulate the proliferation of basal cells.

Merkel

_____ cells occupy the epidermis just prior to innervation along those pathways.

10, 10.5

At around __ to __ weeks EGA, basal cells of the epidermis begin to rapidly divide.

Ledges

As the basal cells proliferate, shallow “_____” can be seen on the bottom of the epidermis which already delineate the overall patterns that will become permanently established on the volar surfaces several weeks later

Primary ridges

During embryonic development, _____ _____ are the first visual evidence of interaction between the dermis and epidermis.

Active cell proliferation

The prevailing theory of events prior to the visualization of primary ridge structure involves centers of _____ _____ _____.

10.5, 16

Initial formation of primary ridges begins at about __ weeks EGA and continues until about __ weeks EGA, at which time secondary ridges begin to form.

Bifurcations would occur as a mechanical separation in the first theory versus a static formation in the second.

What is the difference between the two theories of minutiae formation during fetal development?

14

Sweat glands begin to appear around __ weeks EGA as the existing primary ridges increase in width and continue to penetrate the dermis

15

By _ weeks EGA, the primary ridges are experiencing development in two directions: the downward penetration of the sweat glands and the upward push of new cell growth.

15, 17

Between __ and __ weeks EGA, secondary ridges appear between the primary ridges on the underside of the epidermis.

The randomly located minutiae within the fingerprint pattern become permanently set, marking the end of new primary ridge formation.

What event marks the end of the critical stage?

16, 24

Secondary ridges continue to mature from __ to __ weeks EGA.

Primary ridge, secondary ridge

Incipient ridges could be a result of an abnormal transition from _____ _____ formation to _____ _____ formation at about 16 weeks EGA

Incipient ridges

Those primary ridges that are in the earliest stages of development when secondary ridge formation begins would become _____ _____.

24

After maturation of the primary and secondary ridges at __ weeks EGA, anastomoses begin to cross through the dermis, linked primary and secondary ridges and molding the upper portion of the dermis into papillae pegs.

Palm, fingers

The volar pads of the ____ begin to regress first, followed by the volar pads of the _____.

16

By __ weeks EGA, volar pads have completely merged with the contours of the fingers, palms, and soles of the feet.

Physical stresses

The growth and regression of the volar pads produce variable _____ _____ across the volar surface that affect the alignment of the ridges as they first begin to form.

Size, height

The ____, particularly the _____, of the volar pad during primary ridge formation affects the core to delta ridge count of normal fingerprint patterns.

Early

_____ onset of volar pad regression would lead to a volar pad which was in a more regressed state by the time of the onset of primary ridge formation, and a lower ridge count pattern (or arch) would result.

Lower

Later than average onset of primary ridge formation would lead to a _____-than-average ridge count

Timing, environmental

_____ events, rather than _____ factors, play the dominant role in determining total friction ridge count.

Shape, symmetry

The overall _____ and _____ of the finger volar pad when ridges first begin to form determines pattern type.

Whorl, loop, arch

Generally, high and round volar pads form _____ patterns, asymmetrical “leaning” pads form _____ patterns, and low or absent volar pads form _____ patterns.

Critical stage

Any one of the numerous genetic or environmental factors present during the _____ _____ could cause a slight deviation in the normal developmental symmetry of the volar pad, and, therefore, affect the resulting pattern type.

1. The timing of the onset of friction ridge formation with respect to the stage of volar pad regression

2. The degree of volar pad symmetry

What are the two fundamental factors that serve as a starting point during the critical stage of development in determining what pattern will result on a particular finger?

• Irregular volar pad growth or regression

• Unique growth of the bony distal phalanx

• Physical pressure on the digit

What are three possible causes for abnormal patterns? 

Dissociated ridges, dysplasia

A lack of tension across a portion of the pattern could be the cause of _____ _____, or a complete lack of tension across the entire digit might explain _____.

Chromosomal, timing

_____ abnormalities are closely linked with critical _____ events in the development of the nervous system and other important fetal milestones during the 10.5 to 16 weeks EGA critical stage

Deltas

_____ on the palm form along the shoulders of the volar pads, which have mostly regressed into the surface of the palm before the critical stage.

Thenar, hypothenar

The _____ and _____volar pads are the first to regress and are usually completely absent during the onset of primary ridge formation.

Congenital lymphedema

Swelling of the limb during fetal formation

Ridge alignment, minutiae placement, ridge shape, pore location.

Tension during the critical stage conditions _____ _____, stresses across small areas determine _____ _____, and heterogeneous basal cell distribution determines _____ _____ and _____ _____.

Distal transverse flexion crease

The most common area to see disruptions in ridge flow in the palm is the _____ _____ _____ _____ just under the little finger. 

Vestige pattern

Ridge flow opposite to the main flow of the ridge

Distal phalanx

In 1987, Babler found that radial loops and the distinctive ridge flow on the tips of the thumbs are associated with unique shapes in the bony _____ _____.

Distal phalanx

The terminal bone of each finger

Second

Localized stresses (tensions and compressions), resulting from growth of the tissue layers of the digit and interactions with existing ridge fields, create the foundations for _____ level uniqueness.