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FSC300 > Structure - Persistence of Friction Skin and Matrix Composition > Flashcards

Structure - Persistence of Friction Skin and Matrix Composition Flashcards

1
Q

What is another term for friction skin?

A

Volar skin

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2
Q

In what groups of animals is friction skin found in?

A

Primates

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3
Q

List the 5 general descriptions of the skin?

A
  1. One of the largest organs in the body
  2. Performs several functions
  3. Contains skeleton and organs; sensory input
  4. Waste elimination
  5. Largest external organ
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4
Q

List some of the functions of the skin.

3

A
  1. Protection
  2. Sense of touch
  3. Temperature regulation
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5
Q

Define friction skin.

A

A raised portion of the epidermis of the palmar or plantar skin consisting of one or more connected ridge units of friction skin.

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6
Q

To what to areas is friction skin localized?

A

Palmar and plantar

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7
Q

What is the commonly accepted reason for primates having friction skin?

A

Grip

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8
Q

How does friction skin contribute to our ability to grip?

2

A
  1. Easier to pick up small items with hands
  2. Provides traction while walking barefoot
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9
Q

How much of our total skin surface area is accounted for by friction skin?

A

~ 5%

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10
Q

What is contained in each friction ridge unit?

2

A

One sweat gland and one pore

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11
Q

Why is it important to understand friction ridge composition?

A

If an expert is qualified to present evidence related to fingerprinting, they must have a basic understanding of its properties, how it forms and its composition.

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12
Q

Describe friction ridge development at 6 weeks.

2

A

Hand is paddle-like
Volar pads can be seen

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13
Q

Describe friction ridge development at 8 weeks.

A

Fingers separate

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14
Q

Describe friction ridge development at 10 weeks.

A

Digital pads are distinct

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15
Q

Describe friction ridge development at 12 weeks.

2

A

Friction ridges start to develop in basal layer
Volar pads regress

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16
Q

Describe friction ridge development at 17 weeks.

A

Pattern formation complete

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17
Q

What are the only things that friction risges are affected by?

A

Explainable differences.

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18
Q

Give examples of explainable differences that cant affect friction ridges.

6

A
  1. Scarring
  2. Disease
  3. Growth
  4. Weight fluctuations
  5. Skin grafting
  6. Occupation-related issues
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19
Q

How are ridges formed from ridge units?

A

As ridge units grow, they fuse together to form ridges

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20
Q

True or false: All ridge units grow for the same amount of time and at the same rate.

A

False. They all grow for the same amount of time but at different rates

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21
Q

What are sweat pores?

A

Opening on surface of skin from sweat glands

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22
Q

What is poroscopy?

A

The study of the size and shape of pores.

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23
Q

What is edgeoscopy?

A

Study of edges and ridges.

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24
Q

What are incipient ridges?

A

Ridges that were not fully formed at differentiation.

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25
Q

What are incipient ridges also known as?

A

False or nascent ridges

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26
Q

List some characteristics of incipient ridges.

4

A
  1. May not always record at crime scenes or on inked impressions
  2. Not as thick as fully developed ridges
  3. Frequently fragmented
  4. May not contain pores
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27
Q

How many layers of skin is friction skin comprised of?

A

2

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28
Q

What are the two layers that make up the friction skin?

A

Epidermis and dermis

29
Q

Describe the epidermis.

A

15-20 layers of dead cells that are shed off and replaced continuously from the basal layer.

30
Q

What is the basal layer often referred to?

A

The generating layer

31
Q

Describe the process of skin cell migration.

A

Cells created in the basal layer will migrate upward through the other four layers of the epidermis to the surface where they are sloughed off as dead skin cells.

32
Q

How long does the process of skin cell migration and shedding take?

A

~ 1 month

33
Q

How does scarring occur?

A

When there is damage/penetration of the basal layer.

34
Q

List the layers of the epidermis from superficial to deep.

5

A
  1. Stratum corneum (horny)
  2. Stratum lucidum (hyalin)
  3. Stratum granulosum (granular)
  4. Stratum Spinosum (spinous)
  5. Stratum basal(e) (basal)
35
Q

What is the dermis?

A

Thick foundation layer

36
Q

How is the epidermis attached to the dermis?

A

Double row of dermal papillae (“little skin pegs”)

37
Q

List some characteristics of friction skin.

6

A
  1. No sebaceous glands
  2. Eccrine glands only
  3. More sweat glands per square inch than other skin
  4. No hair
  5. Lack of pigmentation
  6. Over-abundance of nerve endings
38
Q

What are the three overall pattern types of friction skin?

A

Arch, loop, whorl

39
Q

Which basic fingerprint pattern does not contain a core?

A

Arch

40
Q

List the basic pattern types from most to least common.

A
  1. Loop
  2. Whorl
  3. Arch
41
Q

What affects the development of friction ridge patterns?

A

Tension and pressure on volar pads during fetal development

42
Q

What volar pad positioning is associated with a whorl pattern?

A

High volar pad

43
Q

What volar pad positioning is associated with the loop pattern?

A

Intermediate pad

44
Q

What volar pad positioning is associated with an arch pattern?

A

Low volar pad

45
Q

Do identical twins have the same fingerprints?

A

No

46
Q

List some damaging effects to friction skin.

4

A
  1. Injury
  2. Disease
  3. Amputation
  4. Mutilation
47
Q

What are the five basic characteristics that combine to produce ridge patterns?

A
  • Ridge ending
  • Bifurcation
  • Ridge dot/unit
  • Short ridge/island
  • Enclosure/lake
48
Q

Describe fingerprint composition.

A

Combination of different sources, including naturally secreted materials like sweat, sebum or lipids, and foreign materials picked up through daily contact with items and surfaces outside the body.

49
Q

What are the three sources of natural secretion in the human body?

A
  • Eccrine glands
  • Sebaceous glands
  • Apocrine glands
50
Q

What two natural sources of secretion are significant for friction ridge identification?

A

Eccrine and sebaceous glands

51
Q

Why aren’t apocrine glands considered significant for fingerprint identification?

A

Primarily found in underarm and genital areas.

52
Q

Describe the composition of eccrine sweat.

A

98.5%-99.5% water
0.5%-1.5% solids

53
Q

What solid materials can be found in eccrine sweat?

A

Inorganic salts and organic substances

54
Q

Where on the body are sebaceous glands found?

A

Areas associated with hair follicles

55
Q

Describe the composition of sebum.

A

Comprised mainly of saturated fats, waxes and squalene.

56
Q

List some foreign materials that are commonly found in a fingerprint deposit.

6

A
  • Blood
  • Paint
  • Automotive lubricants
  • Industrial grease
  • Oil
  • Cooking/food residue
57
Q

List the common factors that can affect the composition of fingerprint secretions and the concentration of certain components.

7

A
  • Rate and duration of sweating
  • Dietary habits
  • Age
  • Gender
  • Physical health
  • Physical exertion
  • Stress
58
Q

How can rate and duration of sweating impact fingerprint composition?

A

Excessive and prolonged sweating can dilute the concentration of solids within the sweat.

59
Q

How can dietary habits impact the composition of fingerprints?

A

Dietary intake influences secretion content, meaning certain food intake or absence can change the composition of secretions.

60
Q

How can age impact fingerprint composition?

A

Concentration of solids within sweat tends to decrease as we age.

61
Q

How can gender affect the composition of fingerprints?

A

Females generally have lower concentrations of solids than males.

62
Q

How can physical health impact fingerprint composition?

A

Can influence sweat quantity, relating back to rate and duration of sweating.

63
Q

How can physical exertion impact fingerprint composition?

A

Physical activity will potentially increase or promote sweating.

64
Q

How can stress impact fingerprint composition?

A

Elevated stress or anxiety has been shown to cause in increase in rate of sweating and concentration of solids.

65
Q

Describe a take away impression.

A

Formed by the removal of material from the surface by fingerprints.

66
Q

What is the method for capturing take-away impressions?

A

Oblique lighting to locate and photograph. Generally do not lift well.

67
Q

Why do take away immpressions generally not lift well?

A

Tape has static charge to it, which will interact with dust or other material.

68
Q

Why do we take elimination fingerprints?

3

A
  1. Incriminate
  2. Corroborate
  3. Eliminate
69
Q

List some methods for obtaining elimination prints.

4

A
  • Rolled - ink impressions C-216 RCMP form
  • Rolled ink - glass and paper method
  • Porelon fingerprint ink pad
  • Avery adhesive shipping labels with black powder

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