Our hair grows from follicles located under the
skin and has two main parts. Part of the hair that remains under the skin
inside the follicle is referred to as the root while the part that protrudes to
the surface (head, arms etc) is known as the shaft. The base of the root (hair
root) is referred to as the hair bulb and is the part through which the base of
the hair receives nutrients for the formation of new cells.
As the base takes in nutrients, new cells are formed and move up the root to become part of the shaft. Over time, these cells also undergo a process referred to as keratinization (maturation process) where they lose their nucleus and fill with a fibrous protein. Therefore, hair can simply be described as strands of keratinized protein.
Main parts/layers of the hair shaft:
Cuticle - This is the outer
part composed of overlapping keratin
Cortex - The cortex
makes up the middle layer. It's also responsible for giving the natural color
of the hair as well as its physical appearance (curves etc)
Medulla - This is the
central core made up of round cells (this is largely present among those with
Apart from macroscopic investigations, the microscopic investigation of hair is a big part of forensic investigations.
However students can use a microscope to observe and study the characteristics
of a hair fiber/strand including pigmentation, scales as well as the pattern of
A stereo microscope is typically used for the
initial examination of hair (mounted and unmounted) before moving on to the
compound microscope. This is because a stereo microscope has been shown to be particularly
ideal for viewing such characteristics as color, shape, texture and length of
hair, which are the eternal characteristics.
A strand of hair - students
can obtain different types of hair such as hair from human body, from a dog,
Using the tweezers, gently pick and place the
hair strand under low power stereo microscope
Observe and try to see if there are differences
between different types of hair
Under the stereo microscope, students will be
able to see the hair structure as a strand that may appear to have tiny fibers
or fragments on its surface. The stereo microscope will not only show the
shape of the hair (twisted etc) and such fragments on its surface, but also the
color of the hair strand. When viewing different types of hair, students will
also be able to differentiate the thickness between different strands.
There are several procedures that can be used to
view different structures of the hair.
Hair Shaft (casting)
Glass microscope slides
Microscope cover slips
A pair of tweezers
A compound microscope
Make a thin layer of nail polish at the central part of a clean glass slide
Using a brush, brush over the nail polish to create an even thin layer of the nail polish
Using the tweezers, place one or several strands of hair on the central part of the slide with nail polish
Allow the slide to stand for about 10 minutes or until the nail polish is tacky-dry
Using the tweezers, pull off the hair strands from the slide
Place the slide under the microscope and observe using low power objectives
* Latex can be used in place of nail polish
This procedure is used for the purposes of
viewing the scale cast of hair strands. Here, the nail polish/latex is used to
attach and retain the scale cast that remains on the slide once the hair
strands are pulled off.
It is worth noting that the purpose of this procedure
is not to view the internal structure of the hair strand, but the outer layer
of hair that contain the scales. Once the hair strands are pulled off, the
scales remain attached onto the slide and can be viewed using lower power
Using this procedure, students have the
opportunity to view different types of hairs and get to differentiate the characteristics
of the scales.
Observing the Medulla Under Compound Microscope
This is a whole mount procedure that involves
viewing the hair strand in order to observe and study the medulla.
A compound microscope
Microscope glass slides and
A pair of tweezers
Place a drop of water at
the center of a microscope glass slide
Using a pair of forceps,
place a few strands of hair onto the drop of water (or any other mountant
Place the slide under the
microscope and observe under low and high power
Compare different types of
hair under the microscope
The medulla is not always present and may not be
seen in some hair. When carrying out whole mount, students will have the
opportunity to compare different hair strands, study the characteristics of the
medulla (fragmented, continuous etc) and determine whether it is missing
Under the compound microscope, students will
view scales on the surface as irregular annular patterns which tend to be
different in appearance when compared with that of animal hair. On the other
hand, a whole mount will show the medulla part of the hair as either broken
(fragmented), continuous or absent.
Observing hair under the microscope (both stereo and compound microscope) can be and easy, fun activity for students. The students get an opportunity to view and study different types of hair and be in a position to identify hair based on its structure.
For instance, through experience, a student will be able to differentiate between human and animal hair as well as determine whether given hair is healthy or mistreated.
Bisbing, R. E. Forensic identification and
association of human hair. In: Forensic Science Handbook. Vol. 1, 2nd ed., R.
Saferstein, ed. Pearson Education, Upper Saddle River, New Jersey, 2002.
Forensic Human Hair Examination Guidelines.
Scientific Working Group on Materials Analysis (SWGMAT. April 2005.)
Lavker RM, Bertolini AP, Freedberg IM et al.
Biology of hair follicles. In: Freedberg IM et al (eds.). Fitzpatrick’s
Dermatology in General Medicine, 5th ed. New York: McGraw-Hill; 1999:230-238.
Leon Augustus Hausman, and Cornell University.
Human Hair Under the Microscope Recent Acquisitions to the Knowledge of Its
Minute Structure, and Their Applications. 1922.
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