1. TWU Department of Biology
Denton, Texas
TWU Department of Biology TWU Department of Biology TWU Department of Biology
ELECTRON MICROSCOPE AS AN INVESTIGATIVE TOOL TO STUDY EFFECT OF HAIR COSMETICS ON HUMAN HAIR
MORPHOLOGY
MAMTA KUMAR AND DR.WESTMORELAND
ABSTRACT
INTRODUCTION
PURPOSE
METHODS
RESULTS
CONCLUSIONS
Hair Shaft: Hair is an epidermal structure
consisting of the hair follicle and the hair shaft. The
hair shaft has three major parts; from the outside to
the inside they are: the cuticle, the cortex and the
medulla (see fig. 1). Hair is made up of protein,
lipid, water, melanin, and trace elements. The
cortex is the main bulk of the hair, which is made of
keratin filaments arranged parallel to longitudinal
axis of the hair shaft. Multiple keratin filaments
make covalent disulphide bonds between the
sulphur-containing amino acid molecules of
cysteine. Disulphide bonds are responsible for the
shape, stability, and texture of the hair. The cuticle
is made up of 6-8 layers of flattened overlapping
cells with their free edges pointing upward to the
tip of hair shaft (see fig. 1). Normal hair has a
smooth appearance, which allows light to reflect
and is responsible for the luster and texture of the
hair (see fig. 2). The hair follicle is not affected in
cosmetic hair procedures or treatments, but the hair
shaft may be affected (Sinclair 2007).
Hair weathering: Hair weathering is the
progressive degeneration of hair from root to the tip
due to environmental and cosmetic factors. For
example, free margin of the cuticle cells lift up and
break irregularly, thus altering hair texture (see
figures 3,4,10,11). Similarly, many keratin fibers
lose overlapping cuticle cells and show longitudinal
fissures (see fig. 5). In severely damaged hair,
cortical cells may be totally exposed giving a ‘split
ends’ appearance sometimes looking like a paint
brush (Dawber 2002).
Cosmetic Chemicals: Hair cosmetics alter anatomy
of the hair fiber. For example, hydrogen peroxide
used in hair bleach is an oxidizing agent,
responsible for altering the physical properties of
the hair, which is visible under the electron
microscope as weathering of the hair shaft (Dawber
2002).
DISCUSSION
This research paper is my reflection on the inquiry
method of learning science, using the scanning
electron microscope as the investigation tool. This
study was an attempt to find the effect of various
chemicals used in hair cosmetics on the
morphology of human hair. The hair shaft consists
of an outer lipid epicuticle and a layer of flattened
cuticle cells surrounding the elongated cortical
cells. Some chemicals used in hair products cause
progressive degeneration of cuticle cells in the
form of longitudinal fissures. The hypothesis
tested in this experiment is that chemicals such as,
alcohol, hydrogen peroxide, vinegar and lemon
juice alter hair morphology. The control of the
study is untreated scalp hair of a 4-year-old girl.
Hair samples from the same source were treated
with chemicals for a fixed duration of time. The
hair morphology micrographs from this study are
also compared with published micrographs.
This study was an attempt to find the effect of hair
cosmetics on the morphology of hair. Hair cosmetics may
alter hair morphology and accelerate the weathering of hair.
In addition, this study focused on using the electron
microscope as an investigation tool for implementing the
inquiry method of learning science. This experimental
research was the pilot project and was developed through an
initial experience of exploring different hair samples from
various sources such as, human scalp hair, dog, and cat hair
(See figures 6,7,8) . Therefore, the questions generated
during the research and my prior experience with hair
cosmetics helped me begin my journey towards using the
electron microscope as the inquiry tool to study hair
morphology.
Electron Micrographs human scalp hair
Based on the comparison of
electron micrographs, it appears
that alcohol causes maximum
weathering of hair cuticle in the
form of broken cuticle, followed
by hydrogen peroxide, and lemon
juice. However, vinegar does not
cause any weathering of hair
cuticle.
Fig 3. SEM showing minimal
weathering of cuticle with chipped
cuticle cells
Fig 5 SEM showing severe
weathering and loss of the cuticle
Fig 1,2,3, 4 : Published Micrographs of Human Hair
(Harrison and Sinclair 2004)
Fig 2 .SEM of normal overlapping
cuticle cells
Fig 4 Scanning Electron
micrograph showing
weathering of cuticle with
lifting of cuticle cells
Scalp hair samples of a 4yr old girl were treated with each
of the following: hydrogen peroxide (3%), white vinegar,
lemon juice (Readymade commercial brand), and
isopropyl alcohol (50%). The hair samples were left in the
cosmetic chemical overnight (12 hours) and electron
micrograph pictures were compared to published
micrographs.
From left to right - Fig 9, 10, 11 – Hair sample treated with Alcohol – at Magnifications – 1000X, 2000X and 5000X
From left to right - Fig 12, 13, 14 – Hair sample treated with Hydrogen Peroxide – at Magnifications – 500X, 1000X and 1500X
From left to right - Fig 15, 16, 17 – Hair sample treated with Lemon Juice – at Magnifications – 1500X, 2500X and 4000X
From left to right - Fig 18, 19, 20– Hair sample treated with Vinegar – at Magnifications – 1000X, 1500X and 4000X
Hair samples treated with alcohol, hydrogen peroxide and lemon juice accelerate weathering of hair
cuticle as visible in electron micrographs (see figures 9-17). However, vinegar does not alter the
morphology of hair (see figures 18-20). In addition, the hair samples from different mammals show
distinct structural differences as visible in the electron micrographs in the form of thickness of hair
and arrangement of cuticle cells on the hair shaft (see figures 6-8). However, more research is required
for identifying hair samples from different animals.
This study is the pilot project
inspired by initial exploration of
different hair samples from a dog, a
cat, and a human. It is difficult to
draw final conclusion about which
hair chemical used in the
experiment caused hair weathering
due to many reasons. For example,
the micrographs compared are at
different magnifications due to
charging of the hair sample. In
addition, the assumption was made
that the hair sample was
undamaged and that the hair
weathering was induced only by
the chemicals used in the study. An
attempt was made to reduce
charging of the hair sample by
using liquid carbon and by
adjusting the height of the stub.
However, the charging continued
and the cause of charging was
unpredictable. Many questions
remain unanswered during the
study and finding answers to these
questions will be the scope for
future studies. For example, is it
possible to measure the hair
dimensions and use these
measurements in forensic science?
Does hair from different body parts
of the same animal has same
structure and dimensions? Is it
possible to reverse the weathering
of hair caused by the use of hair
cosmetics? Therefore, this pilot
project provided a true inquiry-
based learning experience and
could be the basis for further
research in studying the effect of
hair cosmetics on structure of hair.
Harrison and Sinclair. 2004. Hair colouring, styling and
structure. J Cosmet Dermatol. 2:180-185.
Sinclair R. 2007. Healthy Hair: What is it? J Investig
Dermatol Symp Proc. 12:2-5.
Dawber R. 2002. Cosmetic and medical causes of hair
weathering. J Cosmet Dermatol. 1:196-201.
Fig 1. Hair Shaft Cross Section. Available from:
http://www.hairremoval4guys.com/images/Hair_Shaft_Cross_Section.jpg.
Fig 6. Untreated Human scalp Hair sample – Control - 1000X Fig 7. Cat Hair - 1000X Fig 8. Dog Hair – 1000X
ACKNOWLEDGEMENTREFERENCES
My sincere thanks to
Dr.Westmoreland for facilitating
this study and providing the true
inquiry based learning experience.
Also, I thank Ms.Cathy Boyles
(Wildlife Administrator) for
helping me search research
information on mammalian hair.