Morphology pattern recognition lecture 3 8/28/24

Learning Objectives

Morphology is defined as "the study of the forms of things". As this applies to Friction Ridge Skin we will:

  • Learn about the factors that influence the growth and formation of friction ridge skin.

  • Discuss and explore how these factors contribute to the variation that is observed in friction ridge skin.

  •  Observe and recognize the different pattern types that are present in friction ridge skin.


Discrimination and Persistence*

The use of friction ridge skin as a means of identification is rooted in the conceptual understanding of discrimination and persistence.


  • Discriminating in that no two individuals have been found to have the same arrangement of friction ridge detail and that there are specific aspects of friction ridge skin that allow it to stand apart from a similar arrangement of friction ridge skin.

  • Persistent in that from fetal development until decomposition after death, the friction ridges remain largely the same, only increasing in size until one reaches adulthood.


We see the application of these principles through the morphology of friction ridge skin.


Discrimination: recognition and understanding of the difference between one thing and another - Oxford Languages dictionary


Embryology - Concept of Biological

Uniqueness

• Biological Uniqueness is a concept that the overall

"Uniqueness" of an individual is determined within the biological makeup of that organism. That biological makeup is rooted within their genetics.


• In humans as it pertains to fingerprints, genetics dictate the environment (stability) in which the developmental noise (variation) can take place.


Embryology - Formation of FRS

  • The basis of persistence lies in morphology and physiology whereas the basis of uniqueness lies in embryology.

  • From 0 - 12 EGA the embryo undergoes changes, starting with rapid cell division known as cleavage and by week 12 the embryo's nervous systems and organs develop.

  • Friction ridge skin uniqueness is related to biological uniqueness.

  • Friction ridges begin to form at about 10.5 weeks EGA







Embryology - Volar Pads

  • Primarily at EGA (early gestational age) 7-8 weeks, this is when the volar pads begin to form.The volar pads are the areas of skin that the friction ridges (which make up fingerprints, palm prints and footprints), will form on.

  •  Volar pads are visible in the areas where friction ridges will be and can be considered a "template" for the friction ridges to later form on top of.


Embryology - Volar Pads

  • Primarily at EGA (early gestational age) 7-8 weeks, this is when the volar pads begin to form.The volar pads are the areas of skin that the friction ridges (which make up fingerprints, palm prints and footprints), will form on.

  • Volar pads are visible in the areas where friction ridges will be and can be considered a "template" for the friction ridges to later form on top of.


Volar Pads

After 9-10 weeks EGA, the volar pads which have grown in size begin their regression.


  • During regression, the volar pads stop their growth and begin to keep their final shape.

  •  By 16 Weeks EGA regression is complete.


Differentiation of FR Skin


Epidermis

  • The primitive Epidermis is established by 1 week EGA, with the second layer formed at approximately 4-5 week EGA.

  • The epidermis is a few cells thick but without any clearly defined shape -it is smooth- this is important.


Dermis

• Fibroblasts are the first to differentiate from the mesoderm. As such, these lay the structural groundwork for the dermis. This occurs at about 4 - 8 weeks EGA Nerves begin to appear at 9 weeks EGA. The vascular network at this point has already begin to make the necessary changes within and occurs from 8- 20 weeks EGA


Primary Ridge Formation

  •  At approximately 10-10.5 weeks EGA the basal cells of the epidermis begin to rapidly divide. This can continue until about 16 weeks EGA.


  •  Simultaneously, the cells on the volar pads begin to form shallow "ledges" hereby setting the blueprint for the primary ridges to form.


Secondary Ridge Formation

  •  At 15 weeks EGA primary ridges grow in two directions: downward (inner) and upward.

  • Between 15 - 17 weeks EGA secondary ridges appear between the primary ridges on the underside of the epidermis, and between the primary ridges (themselves).

  • Dermal Papillae form at approximately 23 weeks EGA and continue through adulthood.



Factors of Pattern Formation

  • Volar pad shape is dependent on volar pad height, position, timing of events, stresses across the skin and symmetry of that stress.


  • As such the position of the volar pad, as well as the onset and completion of volar pad regression all influence the pattern type (and formation) that would result.


So... what about the effect of Genetics? 

 (main things different weeks of it happening, what is considered normal) missing eyes ears genetic defeat change into development noise 


The effect of genetics on pattern formation and pattern type is one that is vaguely understood.


As such, there are numerous genes that influence even more specific functions and aspects of friction ridge skin formation that cannot be directly contributed to one gene.


  • • Genetics plays a role in the genetic blueprint whereas nature provides the boundaries for such patterning.

  • • As such, genetics contributes to the developmental noise that is observed in friction ridge prints.

Twins who have the same DNA have different, albeit similar fingerprints.


Developmental Stability and Developmental Noise

• Developmental noise is a concept within developmental biology in which the phenotype varies between individuals even though the genes and natural environment are the same.

• Examples include: cow nose print (used to identify cattle), pattern and arrangement of butterfly wings, zebra stripes etc.

• This is different from Developmental stability which refers to what is considered genetically stable and within a population. (Population entirety of human race or breed of dogs what we are talking about )


Evidence of Developmental Noise in FRS

Ridge path: fetal volar pads play a substantial role in effecting pattern formation and ridge count.

• Localized stresses (stresses due to the timing of events) play a role.


Ridge Morphology: functionally impossible to replicate, the ridge morphology of an individual may appear similar to others-especially relatives.

• However, given that the ridge morphology is rooted within the structure of the skin and established during fetal development it is especially difficult to repeat -if at all-, thus allowing it to be discriminating


Conclusion

  • The morphology of FRS is the product of a meticulously orchestrated process in which time, positioning and genetics all play a role in the appearance of FRS.


  • This process is carried out within the framework of the genetic blueprint and developmental noise influences the details of the FRS.