CELLULOSE
CELL TYPES
Despite their fundamental similarities in structure, the cells
of the body are differentiated so that they can perform a variety
of specific tasks, such as carrying oxygen (red blood cells),
destroying invading microorganisms (white blood cells),
and making hormones (secretory cells in glands). Some cells
(nerve cells, for instance) cannot be replaced once they have
been destroyed, while other cells (those that form toe- and
fingernails, for instance) regrow and continue to function even
after a person’s death. There are four main types of cells,
which are grouped according to their primary functions.
C e ll m e m b r a n e
E n d o p l a s m i c
r e t ic u lu m
M ic r o t u b u le
P e r o x i s o m e
N u c l e a r m e m b r a n e
Epithelial cells
These make up the
tissuesthat cover the
outside ofthe body
and line the digestive,
respiratory, and urinary
tracts. The epithelium
includes glandular tissue,
which is specialized
for secretion.
.
M i c r o f i l a m e n t
M it o c h o n d r io n
V illu s
N u c l e o l u s
Blood cells
Red and white blood
cells, and platelets,
circulate individually
in the blood to carry
nutrients and combat
infection and injury.
V e s i c l e s e c r e t i n g
e n z y m e s a t c e l l s u r f a c e
N u c le u s
R i b o s o m e s
Muscular tissue
Muscle is formed from different types of
muscle cells that are specialized to contract.
L y s o s o m e
Cells in the nervous tissue
G o l g i
These cells conduct electrochemical
c o m p l e x
messagesthroughoutthe body.
C
w hich produce antibodies. T-lympho-
cytes
recognize
specific
antigens
(substances that the body identifies as
foreign), including
cancer
cells and
cells infected by viruses. One group of
T-lymphocytes, known as killer T-cells,
attach themselves to the abnormal cells
and release toxic proteins that destroy
them. (See also
humoral immunity.)
cellular pathology
See
pathology, cellular.
cellulite
The popular term for the subcutaneous
fat that gives the skin a dimpled, or
orange-peel, appearance, especially on
the thighs and buttocks. Cellulite usual-
ly affects women rather than men and
is often attributed to water retention.
cellulitis
A bacterial infection of the skin and the
tissues beneath it, w hich usually affects
the lower legs but can occur anywhere
on the body. Cellulitis is most com-
m only caused by streptococci bacteria,
w hich enter the skin via a wound.
SYMPTOMS
There may be fever and chills; and the
affected area is hot, red and swollen.
Cellulitis is more severe in people with
reduced immunity, such as those who
have an
immunodeficiencydisorder
.
Untreated cellulitis at the site of a
wound may progress
to
bacteraemia
(bacterial infection of the blood) and
septicaemia
(blood poisoning). Facial
infections may spread to the eye socket.
TREATMENT
Treatment of cellulitis is w ith an
anti-
biotic drug
such as a
penicillin
drug or
erythromycin
.
(See also
erysipelas
. )
cellulose
A
carbohydrate
consisting of chains of
glucose (a simple sugar). Cellulose is
the
main
constituent
of
plant-cell
walls. Because it cannot be digested,
cellulose is an important source
of
dietary fibre (see
fibre, dietary
) .
153
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