PERIPHERAL NERVES
p e rip h e ra l n e rv e s
N e rv e s
t h a t r u n b e t w e e n t h e
c e n tra l n e r -
v o u s s y s t e m
( C N S , t h e b r a i n a n d s p i n a l
c o r d )
a n d p a r t i c u l a r
b o d y
t i s s u e s .
O f
t h e s e , 1 2 p a i r s a r e
c ra n ia l n e rv e s
a n d 3 1
p a i r s a r e
s p in a l n e rv e s .
S o m e p e r i p h e r a l
n e r v e s
a r e
s e n s o r y ,
c a r r y i n g m e s s a g e s
f r o m s e n s o r y o r g a n s a n d n e r v e e n d i n g s
( s e e
re c e p t o r
)
t o w a r d s
t h e
b r a i n
a n d
s p i n a l
c o r d ; o t h e r s
a r e
m
o t o r n e r v e s ,
c a r r y i n g s i g n a l s a w a y f r o m t h e C N S t o
s t i m u l a t e r e s p o n s e s i n t h e t i s s u e s .
p e rip h e ra l n e rv o u s s y ste m
T h e s y s t e m
o f
p e r ip h e r a l n e rv e s ,
w h i c h
f a n o u t f r o m t h e
c e n tra l n e rv o u s s y s te m
( t h e b r a i n a n d s p i n a l c o r d ) t o t h e m u s -
c l e s , s k i n , i n t e r n a l o r g a n s , a n d g l a n d s .
p e rip h e ra l v a s c u la r d is e a s e
N a r r o w i n g o f a r t e r i e s i n t h e l e g s , a n d
s o m e t i m e s i n t h e a r m s , w h i c h r e s t r i c t s
b l o o d f l o w a n d c a u s e s p a i n . I n s e v e r e
c a s e s ,
g a n g r e n e
( d e a t h
o f t i s s u e s
s u p -
p l i e d b y t h e v e s s e l s ) m a y d e v e l o p .
CAUSES
I n m o s t a f f e c t e d p e o p l e , p e r i p h e r a l v a s -
c u l a r d i s e a s e i s c a u s e d b y
a t h e ro s c le ro s is
,
i n w h i c h f a t t y d e p o s i t s f o r m o n t h e i n n e r
w a l l s o f a r t e r i e s . T h e g r e a t e s t r i s k f a c t o r
f o r d e v e l o p i n g a t h e r o s c l e r o s i s i s
s m o k in g .
O t h e r
r i s k
f a c t o r s
i n c l u d e
h y p e rte n s io n
( h i g h
b l o o d p r e s s u r e ) ,
a h i g h - f a t
d i e t ,
a n d
p o o r l y
c o n t r o l l e d
d ia b e t e s m e llitu s.
PERIPHERAL
P
VASCULAR DISEASE
The disease usually starts with the
formation of atheroma (fatty plaques)
in the lining of artery walls. Smokers
are among those at highest risk.
Clot formation
Clots mayform on top of the atheroma
(plaques), restricting blood flow to tissues,
which may lead to pain and tissue death.
D i s e a s e s o f t h e p e r i p h e r a l a r t e r i e s t h a t
a r e n o t c a u s e d b y a t h e r o s c l e r o s i s i n c l u d e
B u e r g e r ’s d is e a s e
a n d
R a y n a u d ’s d is e a se .
SYMPTOMS AND COMPLICATIONS
T h e f i r s t s y m p t o m o f n a r r o w e d a r t e r i e s
d u e
t o
a t h e r o s c l e r o s i s
i s
u s u a l l y
a n
a c h i n g f e e l i n g i n t h e l e g m u s c l e s ( u s u -
a l l y i n t h e c a l f ) w h e n w a l k i n g . T h e p a i n
m a y
b e
r e l i e v e d
b y r e s t i n g
f o r
a f e w
m i n u t e s ,
b u t
r e c u r s
a f t e r
t h e
s a m e
a m o u n t o f w a l k i n g a s b e f o r e . P r o l o n g e d
u s e o f t h e a r m s m a y a l s o c a u s e p a i n .
S y m p t o m s t h e n b e c o m
e w o r s e u n t i l ,
e v e n t u a l l y ,
p a i n
i s
p r e s e n t
e v e n w h e n
t h e p e r s o n i s a t r e s t . T h e p a i n m a y b e
s e v e r e a n d c o n t i n u o u s , e v e n d i s r u p t i n g
s l e e p . B y t h i s s t a g e , t h e b l o o d s u p p l y t o
t h e a f f e c t e d l e g i s d a n g e r o u s l y l o w . T h e
a f f e c t e d l i m b i s
c o l d a n d n u m b , w i t h
d r y , s c a l y s k i n , a n d
le g u lc e rs
m a y d e v e l -
o p a f t e r e v e n m
i n o r i n j u r i e s . I n t h e f i n a l
s t a g e ,
g a n g re n e
( t i s s u e d e a t h ) d e v e l o p s ,
i n i t i a l l y a p p e a r i n g i n t h e t o e s a n d t h e n
s p r e a d i n g u p t h e l e g .
S u d d e n
a r t e r i a l
b l o c k a g e
s o m e t i m e s
o c c u r s , c a u s i n g a c u t e
is c h a e m ia
( i n s u f f i -
c i e n t b l o o d s u p p l y t o a n o r g a n o r t i s s u e ) .
T h i s a r t e r i a l b l o c k a g e m a y b e d u e t o t h e
r a p i d d e v e l o p m e n t o f a c l o t o n t o p o f a
p l a q u e o f a t h e r o s c l e r o s i s , b y a d i s s e c t i n g
a n e u r y s m ( s p l i t t i n g o f a n a r t e r i a l w a l l ) ,
o r b y a n e m b o l i s m a r i s i n g f r o m a c l o t
f o r m e d
i n
t h e
h e a r t
a n d
c a r r i e d
t o
a
p e r i p h e r a l a r t e r y . I t c a u s e s s u d d e n , s e v e r e
p a i n . T h e
a f f e c t e d
l i m b
b e c o m e s
c o l d
a n d p a l e o r b l u e , w i t h n o p u l s e . M o v e -
m e n t a n d f e e l i n g i n t h e l i m b a r e l o s t .
DIAGNOSIS AND TREATMENT
A d i a g n o s i s i s o f t e n b a s e d o n t h e r e s -
u l t s
o f
D o p p le r u lt ra s o n o g ra p h y ,
w h i c h
s h o w s t h e f l o w o f b l o o d t h r o u g h t h e
a f f e c t e d v e s s e l s ,
o r
a n g io g ra p h y ,
w h i c h
w i l l r e v e a l s i g n s o f n a r r o w i n g o r o t h e r
s t r u c t u r a l a b n o r m a l i t i e s .
E x e r c i s e a n d g i v i n g u p
s m o k i n g
a r e
i m p o r t a n t
a s p e c t s
o f
t r e a t m e n t .
F o r
p e r i p h e r a l v a s c u l a r
d i s e a s e o f t h e l e g s ,
t h e a f f e c t e d p e r s o n n e e d s t o t a k e s c r u p u -
l o u s c a r e o f t h e f e e t i n o r d e r t o p r e v e n t
i n f e c t i o n a n d m i n i m i z e t h e r i s k o f g a n -
g r e n e .
A rt e ria l re c o n s tru c t iv e s u rg e ry , b y -
p a s s
s u r g e r y , o r b a l l o o n
a n g io p la s ty
m a y
b e n e e d e d t o w i d e n o r b y p a s s t h e a f f e c t -
e d b l o o d v e s s e l s .
A m p u ta tio n
i s n e c e s s a r y
i f g a n g r e n e h a s d e v e l o p e d .
p e ris t a ls is
W a v e l i k e
m o v e m e n t
c a u s e d
b y
t h e
r h y t h m i c c o n t r a c t i o n a n d r e l a x a t i o n o f
t h e s m
o o t h m u s c l e s i n t h e w a l l s o f t h e
d i g e s t i v e t r a c t a n d t h e u r e t e r s . P e r i s t a l s i s
i s r e s p o n s i b l e f o r t h e m o v e m e n t o f f o o d
a n d w a s t e p r o d u c t s t h r o u g h t h e d i g e s -
t i v e s y s t e m a n d f o r t r a n s p o r t i n g u r i n e
f r o m t h e k i d n e y s t o t h e b l a d d e r .
I n t h e d i g e s t i v e s y s t e m , p e r i s t a l s i s i n
t h e
o e s o p h a g u s
( g u l l e t )
m o v e s
f o o d
t o w a r d s t h e s t o m a c h , e v e n i f t h e b o d y i s
PERISTALSIS
The walls of many body passages
contain a special type of muscle
called smooth muscle. The muscle
fibres contract in sequence, sending
waves of contraction along the walls
of the passage.
R e l a x e d m u s c l e
O e s o p h a g u s
,
F o o d
b o l u s
Effect of peristalsis
As each group of muscle fibres in the wall of
the intestinel contracts, it narrows that part
ofthe passage, squeezing the food bolus
into an adjoining section where the muscle
fibres are relaxed.
L a r g e
i n t e s t i n e -
Sites of peristaltic action
Peristalsis occurs most obviouslyin the
digestive tract, shown above, but it also moves
urine through the ureters.
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