Webster's New World Medical Dictionary

rhinorrhea
See 
nose, runny.
RhoGAM
RhO(D) immune globulin, an
injectable drug that is used to protect an Rh+ fetus
from antibodies in an Rh- mother’s blood and to
prevent Rh allergy in the mother.
rhythm method
See 
natural family planning.
rib
One of the 12 paired arches of bone that form
the skeletal structure of the chest wall (the rib cage).
The ribs attach to the vertebrae of the spine in the
back. The 12 pairs of ribs consist of 7 pairs of ribs
that attach to the sternum in the front and are known
as true, or sternal, ribs; and 5 pairs of lower ribs that
do not connect directly to the sternum and are known
as false ribs. The upper 3 false ribs connect to the
costal cartilages of the ribs just above them. The last
2 false ribs usually have no anchor in front and are
known as floating, fluctuating, or vertebral ribs.
rib, cervical
An extra rib that arises from the sev-
enth cervical vertebra. It is located above the nor-
mal first rib. A cervical rib is present in only about
1 in 200 people. It may cause pinching of nearby
nerves or arteries, in which case it sometimes is
removed surgically.
rib, false
See 
false rib.
rib, floating
See 
false rib.
rib, fluctuating
See 
false rib.
rib, sternal
See 
true rib.
rib, true
See 
true rib.
rib, vertebral
See 
false rib.
ribonucleic acid
A nucleic acid that is similar to
DNA but contains ribose rather than deoxyribose.
Abbreviated RNA. RNA, in fact, can form upon a DNA
template. The several classes of RNA molecules play
important roles in protein synthesis and other cell
activities. See also 
messenger RNA; RNA, riboso-
mal; RNA, transfer.