SMOOTH MUSCLE
S
EFFECTS OF SMOKING
About 20 per cent of all deaths in the UK are attributed to smoking. The main
harmful effects of smoking are respiratory diseases (lung cancer and COPD) and
cardiovascular diseases (coronary artery disease and peripheral vascular disease).
Smoking also causes a range of other cancers, including cancer of the bladder,
cervix, tongue, larynx, and stomach. Smoking kills around half of all smokers.
-
Cilia
- Cells lining
airways
_ Smoke particles
.
Extra mucus
produced
Cilia dam aged
Smoker
Coalesced
alveoli
How smoking damages the lungs
Smoke particles irritate the lungs’ airways,
causing excess mucus production (top right).
The smoke particles also indirectlydestroythe
walls of the lungs’ alveoli, which merge together
(above right), resulting in a smaller area overall
for oxygen absorption. Both factors reduce lung
efficiency. In addition, tar in tobacco smoke has
a direct cancer-causing action.
S m o k i n g
i s
e x t r e m e l y
h a r m f u l
d u r i n g
p r e g n a n c y .
B a b i e s
o f
w o m
e n
w h o
s m o k e a r e s m a l l e r a n d a r e l e s s l i k e l y t o
s u r v i v e t h a n t h o s e w h o s e m o t h e r s a r e
n o n s m o k e r s . C h i l d r e n w i t h p a r e n t s w h o
s m o k e
a r e
m o r e
l i k e l y t o s u f f e r f r o m
a s th m a
o r o t h e r r e s p i r a t o r y d i s e a s e s .
T h e r e
i s
a l s o
e v i d e n c e
t h a t
p a s s iv e
s m o k e rs
a r e a t i n c r e a s e d r i s k o f t o b a c c o -
r e l a t e d d i s o r d e r s . A l s o , p a s s i v e s m o k e r s
s u f f e r
i m m e d i a t e
d i s c o m f o r t
w h e n
b r e a t h i n g i n s m o k e a s d e m o n s t r a t e d b y
c o u g h i n g , w h e e z i n g , a n d s o r e e y e s .
T o b a c c o i s
k n o w n t o
c o n t a i n m a n y
t o x i c c h e m i c a l s . A d d i c t i o n t o t o b a c c o i s
c a u s e d
b y
n ic o t in e .
N i c o t i n e
a c t s
a s
a
t r a n q u i l l i z e r
b u t
a l s o
s t i m u l a t e s
t h e
r e l e a s e
o f
a d re n a lin e
i n t o
t h e
b l o o d -
s t r e a m , w h i c h c a n r a i s e b l o o d p r e s s u r e .
T a r i n t o b a c c o p r o d u c e s c h r o n i c i r r i t a -
t i o n
o f t h e
r e s p i r a t o r y
s y s t e m
a n d
i s
t h o u g h t t o
b e
a m
a j o r
c a u s e
o f l u n g
c a n c e r . C a r b o n m
o n o x i d e p a s s e s f r o m
t h e l u n g s i n t o t h e b l o o d s t r e a m , w h e r e
i t e a s i l y c o m b i n e s w i t h
h a e m o g lo b in
i n
r e d b l o o d
c e l l s , i n t e r f e r i n g w i t h
o x y -
g e n a t i o n o f t i s s u e s . I n t h e l o n g
t e r m
,
p e r s i s t e n t l y
h i g h
l e v e l s
o f
c a r b o n
m
o n o x i d e i n t h e b l o o d c a u s e h a r d e n i n g
o f t h e a r t e r i e s , w h i c h g r e a t l y i n c r e a s e s
t h e r i s k o f
c o ro n a ry t h ro m b o s is .
s m o o th m u s c le
A t y p e o f
m u s c le
.
s n a ils a n d d is e a s e
S n a i l s a c t a s h o s t t o a v a r i e t y o f f l u k e s ,
s u c h a s
liv e r flu k e s ,
t h a t i n f e s t h u m a n s .
s n a il tra c k u lc e r
A
s h a l l o w ,
g r e y i s h
m o u t h
u l c e r .
S n a i l
t r a c k
u l c e r s a r e a c h a r a c t e r i s t i c s y m p -
t o m
t h a t
o c c u r
d u r i n g
t h e
s e c o n d a r y
s t a g e o f
s y p h ilis .
s n a k e b ite s
E v e r y
y e a r ,
h u n d r e d s
o f t h o u s a n d s
o f
p e o p l e a l l o v e r t h e w o r l d a r e b i t t e n b y
s n a k e s , b u t t h e c h a n c e o f d e a t h o r s e r i -
o u s i n j u r y f o l l o w i n g a b i t e i s r e l a t i v e l y
s m a l l . M
o s t b i t e s a r e b y n o n v e n o m o u s
s p e c i e s o f s n a k e ; f u r t h e r m o r e , m e d i c a l
t r e a t m e n t o f p o i s o n o u s b i t e s i s u s u a l l y
e f f e c t i v e ,
p r o v i d e d
t h e
v i c t i m
c a n
b e
Snake bite
Following an adder bite, this boy’s arm has become
bruised and swollen, and the lymph nodes in his
armpit have become enlarged.
t a k e n t o h o s p i t a l q u i c k l y . E v e n t h e m o s t
p o w e r f u l
s n a k e v e n o m t a k e s h o u r s
o r
d a y s t o k i l l a h u m a n b e i n g .
VENOMOUS SPECIES
V e n o m o u s s n a k e s a r e f o u n d m a i n l y i n
t h e t r o p i c s ; t h e o n l y p o i s o n o u s s p e c i e s
n a t i v e t o t h e U K i s t h e a d d e r , a m
e m b e r
o f t h e V i p e r i d a e ( v i p e r f a m i l y ) . R o u n d
t h e w o r l d , t h i s g r o u p o f s n a k e s i n c l u d e s
l a n c e - h e a d e d
v i p e r s ,
w a t e r
m o c c a s i n s
( c o t t o n m o u t h s ) ,
a n d
A m e r i c a n
r a t t l e -
s n a k e s . T h e
s a w - s c a l e d
o r
c a r p e t v i p e r ,
w h i c h i s n a t i v e t o p a r t s o f A f r i c a , t h e
M
i d d l e E a s t ,
a n d t h e I n d i a n s u b c o n t i -
n e n t , p r o b a b l y k i l l s m o r e p e o p l e
t h a n
a n y o t h e r s p e c i e s o f s n a k e .
A n o t h e r g r o u p o f v e n o m o u s s n a k e s ,
E l a p i d a e , i n c l u d e s c o b r a s , c o r a l s n a k e s ,
k r a i t s ,
a n d
m a m b a s .
V e n o m o u s
b i t e s
a r e
c a u s e d
b y
o t h e r
s n a k e s
i n c l u d i n g
A t r a c t a s p i d i d a e ( b u r r o w i n g a s p s ) , H y d r o -
p h i i d a e
( s e a
s n a k e s ) ,
a n d
a
r e l a t i v e l y
s m a l l n u m b e r o f t h e C o l u b r i d a e f a m i l y .
EFFECTS OF A BITE
T h e e f f e c t s o f a v e n o m o u s b i t e d e p e n d
o n t h e s p e c i e s a n d s i z e o f t h e s n a k e , t h e
a m o u n t o f v e n o m i n j e c t e d , a n d t h e a g e
a n d h e a l t h o f t h e v i c t i m .
A b i t e f r o m a v i p e r s u c h a s a r a t t l e -
s n a k e
i s
c h a r a c t e r i z e d b y t w o
d i s t i n c t
p u n c t u r e w o u n d s . T y p i c a l l y , t h e r e i s a n
i m m e d i a t e b u r n i n g p a i n a n d s w e l l i n g a t
t h e s i t e , f o l l o w e d b y d i z z i n e s s a n d n a u -
s e a . T h e b l o o d p r e s s u r e d r o p s a n d h e a r t
r a t e i n c r e a s e s . A p i n s - a n d - n e e d l e s s e n s a -
t i o n ,
t h i r s t ,
a n d
h e a d a c h e
a r e
o t h e r
c o m
m o n
s y m p t o m s .
T h e
v e n o m
m a y
p r e v e n t t h e b l o o d f r o m c l o t t i n g , c a u s -
i n g
b l e e d i n g
f r o m
t h e
w o u n d
a n d
b r u i s i n g u n d e r t h e s k i n . T h e r e m a y a l s o
b e i n t e r n a l b l e e d i n g f r o m t h e
u r i n a r y
t r a c t , m o u t h , r e c t u m , o r v a g i n a .
E l a p i d a e a l s o m a k e p u n c t u r e w o u n d s
b u t
m a y
c h e w
t h e
s k i n . T h e i r v e n o m
p r i m a r i l y
a f f e c t s
t h e
n e r v o u s
s y s t e m .
S e r i o u s
s y m p t o m s
d e v e l o p
f r o m
1 0
m i n u t e s t o e i g h t h o u r s a f t e r t h e b i t e a n d
m a y
i n c l u d e
d r o o p i n g
e y e l i d s ,
s l u r r e d
700
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