RECTAL BLEEDING
the attachment of the tooth in the sock-
et may weaken, causing the tooth to
become loose. Severe cases of receding
gums are usually a sign of gum disease
(see
g in g iv it is
;
p e r io d o n t it is
).
re c e d in g h a irlin e
A feature that is characteristic of male-
pattern baldness (see
a lo p e c ia
).
re c e p to r
A general term for any sensory nerve
cell
(one that
converts
stimuli
into
nerve impulses). The term receptor is
also used to refer to specific structures
that occur on the surface of a cell (see
T y p e s of re c e p t o r
box, left)
that allow
chemicals to bind with the cell in order
to exert their effects.
re c e s s iv e
A term used in genetics to describe
one of the ways by w hich a
g e n e
is
passed from parent to offspring. Many
characteristics are determined by a sin-
gle pair of genes, one of each pair
being inherited from each parent. A
recessive gene is
overridden by an
equivalent
d o m in a n t
gene. For example,
the gene for blue eye colour is reces-
sive; therefore, if a child inherits the
gene for brown eyes from one parent
and the gene for blue eyes from the
other, the “blue eye” gene is overrid-
den by the “ brown eye” gene, and the
child ends up w ith brown eyes. The
child must inherit the recessive blue
eye gene from both parents in order to
develop blue eyes.
Many
g e n e t ic d is o r d e r s
are
deter-
mined by a recessive gene. Examples
include
c y s t ic f ib r o s is
and
s ic k le c e ll
a n a e m ia
.
The child w ill only have the
disease if he or she inherits the gene
from both parents.
re c o m b in a n t DNA
A section of
D N A
(genetic material)
from one organism that has been artifi-
cially spliced into the DNA of another
organism, often that of a viral or bacte-
rial cell. This procedure may be carried
out in order to make the recipient cell
produce a substance that it w ould not
normally be able to produce. An exam-
ple of this technique is the addition of
a DNA section containing the genetic
code for the hormone
in s u lin
into a
recipient cell. If this cell can be en-
couraged to replicate, it is possible for
large amounts of the hormone to be
obtained. (See also
g e n e t ic e n g in e e r in g
.)
re c o n s tru c tiv e s u r g e ry
See
a rte ria l re c o n s tru c t iv e s u r g e r y
;
p la s t ic
s u rg e ry .
re c o v e ry p o sitio n
The position in w hich to
place an
unconscious, breathing casualty, while
waiting for medical help to arrive.
The body is placed on its side with
the upper leg bent at a right angle; the
lower leg is kept straight. The lower arm
is bent at a right angle; the upper arm is
bent with the back of the hand placed
against the lower cheek to support the
head, w hich is tilted back to keep the
airway open. Casualties with suspected
spinal injuries should not be placed in
the recovery position.
re c o v e ry ro o m
A hospital unit situated near operating
theatres and delivery rooms that con-
tains specialized equipment and staff
w ho have been trained in the m onitor-
ing and care of postoperative patients
and women who have recently given
birth. Patients leave the recovery room
to return to general nursing care as
soon as they are considered to be in a
sufficiently safe and stable condition.
(See also
in t e n s iv e c a re u n it .)
re c ta l b le e d in g
The passage of blood from the
re c tu m
or
anus.The blood may range in colour from
bright red to dark brown or black. It may
be mixed with, or on the surface of,
fa e c e s
or passed separately. Rectal bleeding may
or may not be accompanied by pain.
H a e m o rrh o id s
(swollen veins in the
lining of the anus) are the most com-
mon cause
of rectal bleeding. Small
amounts of bright red blood appear on
the surface of faeces or on toilet paper.
A n a l f is s u r e
(an ulcer or tear at the mar-
gin of the anus),
a n a l fistu la
(an abnormal
anal channel),
p ro c titis
(inflammation of
the rectum), or
re c ta l p r o la p s e
(protru-
sion of the rectal lining) may also cause
rectal bleeding.
Cancer of the colon (see
c o lo n , c a n c e r
o f
)
or the rectum (see
re c tu m , c a n c e r o f
)
or
p o ly p s
(grape-like growths) can also
cause bleeding. Disorders of the colon,
such as
d iv e r t ic u la r d is e a s e
,
may cause
dark red faeces. Black faeces (see
m e la e -
n a
) may be due to bleeding from high
in the digestive tract. Bloody diarrhoea
may be caused by
u lc e ra tiv e c o lit is
,
a m o e -
b ia s is
,
or
s h ig e ll o s is
.
Diagnosis may be made from a
recta l
e x a m in a tio n
,
p ro c to s c o p y
,
s ig m o id o s c o p y
,
or
c o lo n o s c o p y
(internal examination using a
RECOMBINANT DNA AND GENETICALLY ENGINEERED INSULIN
Genetic engineering can force bacteria to produce human insulin. The insulin gene
is obtained (by removing it from human DNA, then purifying it) and spliced into the
DNA of a bacterium, causing it to produce human insulin. The bacterium is then
cultured for large-scale insulin extraction.
R
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