Page 79 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

Science

What causes a

5 Dry coughing
The air will push out
dry cough? 160km/h (100mph) in
of the lungs at up to
an effort to dislodge
any irritants in the
throat or lungs.
Find out what triggers a Anatomy of
dry cough and how it helps a cough

to keep your airways clear The physical effects of
coughing explained
oughing is an automatic defence refl ex that
helps to keep your airways and lungs clear. 1 Vocal chords open
CThere are two different types; a productive A tickling sensation can cause 4 Epiglottis opens
the vocal chords to open wide
The pressure behind
wet cough, which produces mucus or phlegm, and so that more air is able to enter the epiglottis will
a dry cough, considered nonproductive. the lungs. eventually cause it to
A dry or tickly cough can erupt from the chest open so the air can be
for a number of reasons. It occurs when the throat forcefully expelled.
and upper airways become infl amed, most 2 The lungs
commonly the result of an infection such as cold or expand
flu, but it can also be triggered by irritants (such as The lungs expand

dust, pollen or pet hair) or pollutants in the air. with extra air as
The body assumes this inflammation is a foreign the epiglottis

object partially blocking the airway and initiates closes at the top of
the throat.

the cough reflex in order to remove it.
The vocal chords within the trachea open wide
to allow more air into the lungs. The epiglottis at
the top of the throat will then close off the
windpipe while the abdominal and rib muscles
contract. This increases the pressure behind the
epiglottis, which opens to expel the air at up to 160
kilometres (100 miles) per hour.
k
y
l
c
r
A d
A dry or tickly
y o
r t
i
cough can erupt from 3 Abdominal
muscles contract
the chest for a number The abdominal and
rib-cage muscles then
contract, which causes © Thinkstock
of reasons pressure to build behind
the epiglottis.
How does laser hair removal work?
Does this technique really banish unwanted hair for good?

aser hair removal works by fi ring a should work very well, however, its limitations

specific concentrated light beam at the lie with people that do not have contrasting
Lundesired hair, with a wavelength that hair and skin colours. This means that less of
targets melanin responsible for hair colour and the laser beam is absorbed into the hair,
the hair bulb, where living cells divide to build making the treatment much less effective.
the hair shaft. The laser uses your hair to Even when this technique works it is rarely
absorb heat, which causes infl ammation to permanent; patients need between one and
form around the follicle, effectively killing it. four treatments a year to maintain it. This
As the hairs are not targeted individually, the is because at any one time, a number of
process is much quicker to carry out than your hairs will be in the resting phase of
electrolysis, but may cause damage to the skin growth, meaning that they won’t be affected
Laser hair removal isn’t cheap; a single treatment of a large if it is not carried out correctly. If you are by the laser treatment and will grow
area can cost in the region of £640 ($1,000) relatively pale with dark hair this treatment back again.

How It Works 79