Hair PPT Flashcards
Three types of animal hairs.
Vibrissa
Bristle
Wool
Vibrissa hair:
Tactile and sensitive whisker of many animals, largest and longest hair on body.
Bristle hair:
Coarse bristle or guard hair that provide a protective coat ; can be readily identified, distinctive in appearance and morphology
Wool hair:
Fur hair that provides insulation from wet and cold; shorter finer hairs that cover bodies of all mammals.
Types of hair on human body:
Primodial
Lanugo
Vellus
Terminal
Primodial
Appear at 3rd month of gestation on upper lip, eyebrows, palms and soles of fetus.
Lanugo hair:
Found in fetal life, shed after 6th month of gestation. Smooth surface; observed on aborted fetus and can be used in infanticide investigation.
Vellus hair:
Spread uniformly over body surface. Soft fine unmedullated, rarely exceed 2cm in length. Cover entire body of human except soles of feet, palms of hands, lips and nipples.
Terminal hair:
Coarser hairs that replace vellus at specific sites and times of life; found on scalp, eyebrows, eyelashes, lesser extent on limbs of both sexes at all ages. Puberty accompanied by pubic and axillary hair growth.
Hair is:
Appendage of the skin that grows out of an organ called “hair follicle.”
Root is:
Portion of hair that lies in the follicle, whereas the portion above skin surface is called the “shaft.”
Bulb is:
Enlarged base of the root,which surrounds a mass of loose connective tissue called “dermal papilla.”
Hair is excellent for biological study:
The resist biological and chemical degradation.
Hair is excellent for biological study:
Hair is composed of a group of proteins called “keratins” that interconnect to form stable fibrils.
Hair is excellent for biological study:
Keratin protein chains are complex and produce an integral structure.
Hair is excellent for biological study:
Bonding of sulfur atoms between adjacent keratin chains makes them extremely resistant to degradation.
Microscopic structure of hair:
Cuticle, medulla and cortex
Cortex is:
Inner darker portion of hair
Medulla is:
Canal-like structure in the center of the cortex.
Cuticle is:
Outer layer of scales that surround the hair shaft.
“Color of hair” is due to:
pigment granules in the cortex and air bubbles in the medulla.
Types of Medulla:
Interrupted, Fragmented, Continuous, Absent or not present
Hair growth phases:
Anagen, Catagen and Telogen.
Anagen phase:
80-90 % of follicles
Active growth 2 to 6 years.
Follicle actively producing hair. When pulled, follicle tag maybe present, which is good DNA source.
Catagen phase:
2% of follicles
Transition growth 2 to 3 weeks. Root takes elongated appearance.
Telogen phase:
10-18% of follicles
Resting phase 5 to 6 weeks. Final growth phase in which hair falls out of the skin. Root takes a club-shaped appearance. After 2 to 6 months of growth, hair will naturally shed.
When hair is removed by “Force:”
Anagen phase - follicle tissue from root sheath may still be attached.
When hair is removed by “Force:”
Telogen phase - in resting phase before being shed, could be forcibly removed during an assault, otherwise, no way to tell.
When hair is removed by “Force:”
Only when tissue is attached can it be said the hair was forcibly removed.
Post Mortem:
“Decomposition”
- Color changes
- Loss of soft tissue
- Degradation of cortical structure
Post Mortem:
At decomposition, if anagen hairs are pulled, banding may appear around base of hair.
Post Mortem Banding:
useful to indicate hair was deposited after death, body has been moved or hairs plucked after death and dropped elsewhere.
Identification of human hair:
Species origin, racial origin and body or somatic location.
Species origin:
Scales on “human” cuticular surface are generally small and margins form irregular mosaic. Scales are flattened, outer cuticular margin show little if any serration.
Species origin
“Animals” exhibit wide range of cuticular patterns.
Species origin:
“Human” medulla index is less than 1/3 diameter of hair shaft. Untreated hairs are uniform in color. Pigmentation concentrated toward shaft perihery.
Species origin:
“Animal” medulla greater than 50% of hair shaft. There color changes along the shaft (banding). Pigmentation concentrated around medulla.
Racial origin:
Three major groups:
Caucasoid
Mongoloid
Negroid
Racial origin:
Primarily applied to head hair. Racial mixture, limited sample, size, and poorly defined characteristics may make it difficult to conclude racial origin based on hair.
Identification of hair:
Look for: Structure Color Cuticular traits Length Disease
Identification of hair:
“Length of Cuticle”
- length of each hair should be measured directly
- hair in question must be within range of lengths found in exemplar
- cuticular surface may reveal comparable damage and scale morphology.
Identification of hair:
Hair shaft abnormalities do not occur often. Blood crusts, fibers, dandruff. Diseases - unusual banding along hair shaft owing to presence of numerous small irregular air spaces.
Identification of hair:
Hair can be linked to an individual by DNA in the root or follicular tissue. Pulled hairs have the follicular tag (rich in DNA).
Identification of hair:
In the absence of follicle tissue, examiner relies on hair root.
Identification of hair:
“Anagen” phase has higher rate for DNA extraction. Telogen phase has inadequate amount of DNA.
Collect hairs for examination:
Facial- from mustache,beard and sideburns. Head hair from each of the major regions. Hairs should be pulled from skin. 50 hairs from each region. Vigorous combing or brushing.
Instrumentation:
Stereomicroscope - determine range of characteristics related to hairs. Aid of different temperature illuminators and colored backgrounds, examiner can discriminate specimens in initial color observations.
Instrumentation:
Compound microscope
with higher magnification and resolution, delineate hair’s finer characteristics.
Instrumentation:
Comparison microscope
compare questioned hair samples side by side.
