MMR VACCINATION
THE MECHANISM OF MITOSIS
Mitosis is the simplest type of cell division. It provides new body cells to replace
those that have died. Each of the new cells receives an identical copy of the
chromosomes from the original cell.
N u c l e u s
,
C e ll
m e m b r a n e
1
Chromosomes in a cell nucleus are
invisible, long threads. Before cell division,
the threads replicate, coil up, and shorten,
appearing as dark rods. The two copies of each
chromosome are joined at a point called the
centromere, so they appear X-shaped.
2
The doubled chromosomes line up
in the centre ofthe cell. The cell
nucleus breaks down, and threads
appear in the cell. The two copies of
each chromosome then move apart
along the threads.
T h r e a d s
3
The two identical
groups of single
chromosomes now
gather at opposite
ends ofthe cell, and
a nuclear membrane
forms around each
group. The rest ofthe
cell then divides.
N u c l e a r m e m b r a n e
C h r o m o s o m e
c o p i e s
4
When division has finished and new
nuclei have fully formed in the two
daughter cells, the chromosomes uncoil to
resume their invisible, threadlike form.
Mitosis is now complete.
m itra l s t e n o s is
N a r r o w i n g o f t h e o p e n i n g o f t h e
m i t r a l
v a l v e
i n t h e
h e a r t
.
T h e l e f t a t r i u m ( u p p e r
c h a m b e r )
h a s t o w o r k h a r d e r t o f o r c e
b l o o d
t h r o u g h
t h e
n a r r o w e d
v a l v e .
M i t r a l
s t e n o s i s
i s
m
o r e
c o m
m o n
i n
w o m e n
a n d
m a y
b e
a c c o m p a n i e d
b y
m i t r a l i n c o m p e t e n c e
( f a i l u r e o f t h e v a l v e
t o c l o s e p r o p e r l y ) . I t i s u s u a l l y d u e t o
d a m a g e c a u s e d b y
r h e u m a t i c f e v e r
.
SYMPTOMS
T h e m a i n s y m p t o m i s b r e a t h l e s s n e s s o n
e x e r t i o n .
A s
m i t r a l
s t e n o s i s
w o r s e n s ,
b r e a t h i n g
d i f f i c u l t y
e v e n t u a l l y
o c c u r s
w h e n t h e p e r s o n i s a t r e s t . O t h e r s i g n s
i n c l u d e
p a l p i t a t i o n s
,
a t r i a l f i b r i l l a t i o n
( a
r a p i d ,
u n c o o r d i n a t e d ,
i r r e g u l a r
h e a r t -
b e a t ) ,
a n d f l u s h e d
c h e e k s . T h e p e r s o n
m a y
a l s o
c o u g h
u p
b l o o d
a n d
f e e l
f a t i g u e d . P o s s i b l e
c o m p l i c a t i o n s a r e a s
f o r m i t r a l i n c o m p e t e n c e .
DIAGNOSIS AND TREATMENT
A d i a g n o s i s i s m a d e f r o m
t h e p a t i e n t ’s
h i s t o r y , l i s t e n i n g t o h e a r t s o u n d s , a n d
b y
v a r i o u s
i n v e s t i g a t i o n s
s u c h
a s
a n
E C G
,
c h e s t X - r a y s
,
e c h o c a r d i o g r a p h y
,
a n d
c a r d i a c
c a t h e t e r i z a t i o n
.
D r u g t r e a t m
e n t
i s
b r o a d l y
t h e
s a m e
a s
f o r
m
i t r a l
i n c o m
p e t e n c e .
I f s y m
p t o m
s p e r s i s t , b a l l o o n
v a l v u -
l o p l a s t y
m a y b e c a r r i e d o u t i n o r d e r t o
s t r e t c h
t h e
v a l v e .
A l t e r n a t i v e l y ,
h e a r t -
v a l v e
s u r g e r y
m a y
b e
p e r f o r m
e d
t o
r e p l a c e t h e v a l v e .
m itra l v a lv e
A v a l v e i n t h e l e f t s i d e o f t h e
h e a r t .
T h e
m i t r a l ( o r b i c u s p i d ) v a l v e i s m a d e u p o f
t w o f l a p s , a l l o w i n g o n e - w a y b l o o d f l o w
f r o m
t h e l e f t
a t r i u m
( u p p e r
c h a m b e r )
i n t o t h e l e f t
v e n t r i c l e
( l o w e r c h a m
b e r ) .
m itra l v a lv e p ro la p s e
A c o m m o n , s l i g h t d e f o r m i t y o f t h e
m i t r a l
v a l v e ,
i n t h e l e f t s i d e o f t h e
h e a r t ,
t h a t c a n
p r o d u c e a d e g r e e
o f
m i t r a l i n c o m p e t e n c e
( f a i l u r e o f t h e v a l v e t o c l o s e p r o p e r l y ) . T h e
p r o l a p s e i s m o s t c o m m o n i n w o m e n a n d
c a u s e s a h e a r t
m u r m u r .
I t m a y b e i n h e r i t -
e d , b u t t h e c a u s e i s o f t e n u n k n o w n .
U s u a l l y , t h e r e a r e n o s y m p t o m s . O c c a -
s i o n a l l y ,
h o w e v e r ,
t h e
c o n d i t i o n
m a y
p r o d u c e c h e s t p a i n ,
a r r h y t h m i a
( i r r e g u -
l a r h e a r t b e a t ) , o r , r a r e l y ,
h e a r t f a i l u r e .
O f t e n ,
n o
t r e a t m e n t i s
r e q u i r e d f o r
m i t r a l v a l v e p r o l a p s e , b u t s o m
e p e o p l e
m a y b e t r e a t e d w i t h
b e t a - b l o c k e r d r u g s ,
d i u r e t i c d r u g s ,
a n t i a r r h y t h m i c d r u g s ,
o r ,
r a r e l y ,
h e a r t - v a l v e s u r g e r y
.
m itte ls c h m e rz
L o w e r a b d o m i n a l p a i n e x p e r i e n c e d b y
s o m e w o m e n a t t h e t i m e o f
o v u l a t i o n .
T h e p a i n u s u a l l y o c c u r s o n o n e s i d e o f
t h e a b d o m e n a n d l a s t s f o r o n l y a f e w
h o u r s . I t m a y b e a c c o m p a n i e d b y s l i g h t
v a g i n a l
b l o o d
l o s s .
I n
c a s e s
o f s e v e r e
m i t t e l s c h m e r z ,
o r a l c o n t r a c e p t i v e s
m a y b e
p r e s c r i b e d t o s u p p r e s s o v u l a t i o n .
m ix e d c o n n e c tiv e tis s u e
d is o rd e r
A n
a u t o i m m u n e d i s e a s e
t h a t a f f e c t s t h e
c o n n e c t i v e t i s s u e
( w h i c h s u p p o r t s b o d y
s t r u c t u r e s )
t h r o u g h o u t
t h e
b o d y .
I t
c o m b i n e s f e a t u r e s o f
s y s t e m i c s c l e r o s i s
,
s y s t e m i c
l u p u s e r y t h e m a t o s u s
,
p o l y m y o -
s i t i s
,
a n d
r h e u m a t o i d a r t h r i t i s
.
M i x e d
c o n n e c t i v e
t i s s u e
d i s o r d e r
i s
d i a g n o s e d
b y
b l o o d
t e s t s
t h a t
r e v e a l
a n t i b o d i e s
t o
a
c e l l u l a r
p r o t e i n
c a l l e d
r i b o n u c l e i c p r o t e i n ( R N P ) . T r e a t m e n t i s
s i m i l a r t o t h a t f o r s y s t e m i c l u p u s e r y t h -
e m a t o s u s , w i t h
c o r t i c o s t e r o i d d r u g s
a n d
i m m u n o s u p p r e s s a n t d r u g s
.
M M R v a c c in a tio n
A d m i n i s t r a t i o n
o f a
c o m
b i n e d
v a c c i n e
t h a t
g i v e s
p r o t e c t i o n
a g a i n s t
m e a s l e s
,
m u m p s
,
a n d
r u b e l l a
.
T h e v a c c i n a t i o n i s
o f f e r e d t o a l l c h i l d r e n b e t w e e n
1 2 a n d
1 5 m o n t h s o f a g e , w i t h a b o o s t e r s h o t
a t t h r e e t o f i v e y e a r s . V a c c i n a t i o n i s p o s t -
p o n e d i f a c h i l d i s f e v e r i s h , a n d i t i s n o t
g i v e n t o c h i l d r e n w i t h u n t r e a t e d
c a n c e r
o r
a l l e r g i e s
t o a m i n o g l y c o s i d e
a n t i b i o t i c
d r u g s
s u c h a s
n e o m y c i n .
M i l d
f e v e r ,
r a s h ,
a n d
m a l a i s e
m a y
o c c u r
a f t e r v a c c i n a t i o n .
I n a m
i n o r i t y
o f c a s e s , m i l d , n o n i n f e c t i o u s s w e l l i n g o f
t h e
p a r o t i d g l a n d s
d e v e l o p s t h r e e t o f o u r
w e e k s a f t e r v a c c i n a t i o n . T h e r e i s n o e v i -
d e n c e
f o r
a
l i n k
b e t w e e n
M M R
a n d
C r o h n ’s d i s e a s e
o r
a u t i s m
.
M
511
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