TEMPERATURE METHOD
T
STRUCTURE AND ARRANGEMENT OF TEETH
At the heart of each tooth is the living
pulp, which contains blood vessels
and nerves. A hard substance called
dentine surrounds the pulp. The part
of the tooth above the gum, the
crown, is covered by enamel. The
roots of the tooth, which fit into
sockets in the jawbone, are covered
by a sensitive, bonelike material,
the cementum. The periodontal
ligament connects the cementum to
the gums and to the jaw. It acts as a
shock absorber and prevents jarring
of the teeth and skull when food is
being chewed.
Cross-section
Enamel
Dentine
N eckof tooth
Gum
Pulp
Jawbone
Root
Cementum
Blood vessels
Nerve
Central and
lateral incisors
(7 to 9 years)
Firstand second
prem olars
(10 to 12 years)
Second molars
(11 to 13 years)
Third molars
(17+ years)
First molars
(6 to 7 years)
Canines
(9 to 11 years)
The permanent teeth
The illustration above showsthe arrangement in
the jaw ofthe permanent teeth - eight incisors,
four canines, eight premolars, and 12 molars.
The ages when these teeth erupt are indicated.
X-ray of teeth
The panoramicX-ray on the left shows all the
teeth (there are no wisdom teeth) ofthe upper
and lower jaw and their surrounding structures.
The tooth roots, buried in jawbones, can be
clearly seen; several teeth have been filled.
Molars
The molars are large, strong teeth,
efficient at grinding food. The third
molars, or wisdom teeth, are the
lastto erupt; in some people, the
wisdom teeth never appear.
Premolars
Also known as bicuspids, because of
their two distinct edges, the premolars
are concerned with grinding food.
There are no premolars among the
primary (milk) teeth.
Incisors
These teeth have a chisel-shaped,
sharp cutting edge that is ideal for
biting. The upper incisors overlap
the lower incisors slightly when
the jaws are closed.
Canines
These are sharp, pointed teeth, ideal
for tearing food. They are larger and
stronger than the incisors, with very
long roots. The upper canines are
often known as eye teeth.
a c t i v a t e s m
e c h a n i s m s a u t o m a t i c a l l y t o
c o m p e n s a t e f o r a n y c h a n g e s .
W
h e n
b o d y
t e m p e r a t u r e
f a l l s ,
t h e
h y p o t h a l a m u s s e n d s n e r v e i m p u l s e s t o
s t i m u l a t e
s h iv e r in g ,
w h i c h c r e a t e s h e a t
b y m u s c l e a c t i v i t y . N e r v e i m p u l s e s a r e
a l s o s e n t t o
c o n s t r i c t b l o o d v e s s e l s i n
t h e
s k i n ,
w h i c h
m i n i m i z e s
h e a t
l o s s .
W
h e n t h e b o d y t e m p e r a t u r e r i s e s , t h e
h y p o t h a l a m u s
s t i m u l a t e s
s w e a t in g
a n d
d i l a t e s
( w i d e n s )
b l o o d
v e s s e l s
i n
t h e
s k i n t o i n c r e a s e h e a t l o s s . A l a r g e n u m
-
b e r o f f a c t o r s ( s u c h a s i n f e c t i o n s o r e x -
t r e m e s
o f h e a t a n d c o l d )
m a y d i s r u p t
t h e b o d y ’s h e a t - r e g u l a t i n g s y s t e m , m a k -
i n g
t e m p e r a t u r e
t o o h i g h
o r
t o o
l o w .
( S e e a l s o
f e v e r; h e a ts tro k e ; h y p o t h e rm ia .)
te m p e ra tu re m e th o d
S e e
c o n tra c e p t io n , n a tu ra l m e t h o d s of.
te m p o ra l
A m e d i c a l t e r m m e a n i n g o f o r n e a r t h e
t e m p l e s o r a t e m p l e .
te m p o ra l a rte rit is
A n u n c o m
m o n d i s e a s e o f o l d e r p e o p l e
i n w h i c h t h e w a l l s o f t h e a r t e r i e s i n t h e
s c a l p o v e r t h e t e m p l e s b e c o m e i n f l a m e d .
O t h e r a r t e r i e s i n t h e h e a d a n d n e c k m a y
a l s o b e a f f e c t e d , a s m a y t h e a o r t a
( t h e
732
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