Dermatoglyphics: Skin, Hair, Prints, Fibers, and Burns

Dermatoglyphics (Greek: skin, carve) Ridge formations visible due to lack of hair on palms of hands and soles of feet. Ridges form during the third or fourth month of fetal development- partly genetic, partly from contact between the amnion and the walls of the uterus making dermal ridges called dermal pegs.

Prints are patent (visible), latent (invisible without chemical development), and plastic (impression on a soft material like playdough, clay, or soap)

Unique to the individual. Decomposition is slow here; some ridges have been identified in mummies after thousands of years. Fingers, toes, ears (on a pillow), hands leave prints from secretions of sebaceous, and sudoriferous (sweat)/ceruminous (earwax) glands. Scars, moles, warts, burns.. may leave a mark.

If latent, develop with:

-Powders for hard surfaces (black for light surfaces and grey or fluorescent of dark or colorful surfaces)

-On porous surfaces use 1) iodine fuming -iodine crystals sublimate (solid turns to gas) and react with oils. Disappears quickly unless starch is added to make a blue stain that lasts weeks to months. 2) ninhydrin- reacts with amino acids from sweat and turns purple. 3) silver nitrate ( should only be used after the first two as it washes away amino acids and oils. Reacts with NaCl (salt) from sweat. 4) Superglue/cyanoacrylate fuming- makes white prints that are long lasting after polymerizing in response to water and salts.

Layers:

Epidermis:

Stratum corneum

Stratum lucidum (in thick skin only)

Stratum granulosum

Stratum spinosum

Stratum basale

Dermis-collagen, hair follicles, sebaceous glands, eccrine sweat glands, ridges in papillary layer, blood vessels and nerves, as well as arrector pili muscles, and sensory receptors

Hypodermis (subcutaneous layer of adipose or fat)

Pathologist examines the skin for birthmarks, scars, tattoos or other identifying marks, injuries such as abrasions, cuts, contusions, petechial in sclera of eye and inside oral cavity

Fingerprints: dermatoglyphics classifies hand and footprints. In ancient Babylonia business transactions as early as 500 BC were recorded with fingerprints.

Forks, bifurcations, short ridges, islands, deltas, and ridge endings, dot, bridge, hook (spur), eye (lake), double fork, triple fork, arch (no delta, plain or tented), loops (only one delta, radial or ulnar), and whorls (plain whorl, pocket whorl, double loop whorl…

Hair anatomy: Cuticle, cortex medulla; hair root (DNA) and shaft (no DNA but specific patterns that raise odds to hundreds or thousands to one of a match). Follicle and hair shape change with curly hair (flat) and straight hair (round). Medullary patterns are specific for various species as are cuticular patterns (coronal, spinous, or imbricate).

-Medulla is less than 1/3 present in human hair, greater than 1/3 in most animal hairs. The medulla in human hair is not structures (and not continuous) while in other animals it may be very structured with structural elements related to species.

-color of human hair- little variation along the shaft. Many animal hairs have variation.

Can use morphology to differentiate scalp from pubic hair

Hair has three growing stages:

Anagen- growing

Catagen- slowing

Telogen- not growing, club-shaped ending, easily lost

Can use cross-sectional shape as an indicator of curliness (perhaps race) of hair. Round (very straight), oval (wavy), ribbonlike- (very curly).

Fibers: analyzed via 1) microscopic evaluation for color, texture, shape, pattern, twist, cross-sectional appearance, and surface characteristics, 2) chemical analysis (acid, base, organic solvent such as acetone, oxidizing agents such as bleach/sodium hypochlorite), and 3) flame tests (type of burn, color of flame, type of ash), 4) dye absorbance, as well as 5) melting point, 6) density, 7) tensile strength, 8) scanning electron microscopy (EM), 9) pyrolysis (burning), 10) UV spectroscopy..

Fibers are natural- derived from plant or animal, like wool, cotton, or silk, or man-made (synthetic), like rayon, nylon, acetate, or polyester.

Fibers can be from natural textiles

-knit versus weave, number and color of fibers, threads per inch. Woven fabrics have warp fibers along the length of the loom and weft fibers go back and forth, in and out, to make a checkered woven pattern.

-plain weave- in and out every other warp fiber with

alternating rows

-twill (denim) weave goes over multiple fibers at an angle.

The angle can vary.

-satin- fibers pass over in same pattern making a smoother/shinier surface

-Yarns are filaments with man-made long fibers or short, spun twisted fibers (twists may be right-or left handed with more or fewer fibers)

Synthetic fibers

Petrochemical source- fibers melted and extruded through a mold in cylindrical, pentagonal, octagonal…shapes. Tri-lobed shapes reflect light for a sparkly surface; octagonal shapes resist dirt and are found in carpeting..

-Dyes may penetrate fiber or pigments may just attach to the surface. Some processes dull the shine on the surface with chemicals.

-homopolymers are all the same, while random have different fibers interspersed randomly, alternating have different fibers every other row, block have one fiber repeat several times and then the other fiber repeat several times.

Burns: may be caused by 1) heat, 2) caustic chemicals such as acids or bases, or 3) friction

Classification of first (epidermis only), second (epidermis and dermis, and third degree (layers under the skin)

Need to manage infection and fluid loss. Keep area moist and clean to prevent pathogens and fluid loss. Accomplished using sterile solutions and dressings, and sometimes artificial skin or skin grafts.
Rule of 9s used to estimate percentage of body affected

Chest 18%, Back 18%, legs- 9% for front and 9% for back of each; arms- 4.5% for front of each and back of each (9% for one whole arm); head-4.5% for front and 4.5% for back. Genetalia-1%.

Fluid replacement 4 ml lactated ringer’s solution /kg body weight/total body surface area burned (half to be given in first 8 hours, half in next 16 hours)- then follow urine output to maintain fluids.