2. The Function of Hair Regulates body temperature Decreases friction
Protects against sunlight
Forensic Science: Fundamentals & Investigations, Chapter 3

3. A follicle embedded in the skin produces the hair shaft
The Structure of Hair
A follicle embedded in the skin produces the hair shaft
Three layers (illustrated above):
the inner medulla
the cortex
the outer cuticle
Forensic Science: Fundamentals & Investigations, Chapter 3

4. Skin Structure
Kendall/Hunt Publishing Company

5. Hair Shaft Composed of:
Cuticle—outside covering, made of overlapping scales
Cortex—inner layer made of keratin and imbedded with pigment; also contains air sacs called cortical fusion
Medulla—inside layer running down the center of the cortex
Kendall/Hunt Publishing Company

6. The Cuticle Coronal Spinous Imbricate
outermost layer of hair which is covered with scales.
The scales point toward the tip of the hair.
Scales differ between species of animals and are named based on their appearance.
The three basic patterns are:
Coronal
Spinous
Imbricate
Kendall/Hunt Publishing Cmpany

7. Animal Hair and Human Hair
Spinous Coronal Imbricate
Animals: cuticle scales resemble petals (spinous) or a stack of crowns (coronal)
Humans: commonly flattened and narrow (imbricate)(animals can also have imbricate!)
Forensic Science: Fundamentals & Investigations, Chapter 3

8. The Cortex The cortex gives the hair its shape.
It has two major characteristics:
Melanin—pigment granules that give hair its color. (distribution of pigment varies)
Cortical fusi—air spaces, usually found near the root but may be found throughout the hair shaft
Kendall/Hunt Publishing Company

9. The Medulla
The medulla is the hair core that is not always visible. The medulla comes in different types and patterns.
Kendall/Hunt Publishing Company

10. Types of Medulla
Forensic Science: Fundamentals & Investigations, Chapter 3

11. Types of Hair Arm or Leg Beard Hair Pubic Hair
Buckled Blunt Double Medulla
A cross section: circular, triangular, irregular, or flattened
Shape: influences the curl of the hair
Texture: coarse or fine
Forensic Science: Fundamentals & Investigations, Chapter 3

12. Hair Shape
Can be straight, curly or kinky depending on the cross-section, which may be round, oval or crescent-shaped
Oval
(Curly)
Crescent moon/
Flattened
(Kinky)
Round
(Straight)
Kendall/Hunt Publishing Company

14. The Root
Human roots look different based on whether they have been forcibly removed or if they are telogen hairs and have fallen out. Animal roots will vary, but in general have a spear shape.
Fallen out
Forcibly removed
Kendall/Hunt Publishing Company

15. Treated Hair
Hair can be treated in many different ways.

16. Ethnic or Ancestral Differences
There are some key physical characteristics that are associated with hair of different ancestral groups.

17. Can you identify the animal hairs shown?B C D G E F H I
Teacher Note: I challenge students to identify each hair sample pictured on this slide as they examine the sets of animal hairs I have prepared for them. An observation worksheet is available on my website which requires students to draw an image of what they see and add a description that highlights unique characteristics of each specimen. A key for the animal hairs is available on the next to last slide of this presentation!
Think About It …
In which samples are we viewing the cuticle? How do they compare?
(2) In which samples are we viewing the medulla? How do they compare?
(3) What characteristics can be used to identify hair samples?

18. Types of Animal Hairs - Key
Cat
Horse
Pig
Human A B C D G E F H I
Deer
Dog
Rabbit
Rat
Human