Webster's New World Medical Dictionary

film
Slang shortening of X-ray film.
film, AP
An X-ray picture in which the beams
pass from front to back (anteroposterior). See also
film, PA.
film, lateral
An X-ray picture taken from the
side.
film, PA
An X-ray picture in which the beams pass
from back to front (posteroanterior). See also 
film, AP.
filovirus
A virus in the family filoviridae that
causes hemorrhagic fever. Filoviruses have single-
stranded RNA as their genetic material. Ebola virus
and the Marburg virus are both filoviruses.
fine needle aspiration
The use of a thin needle
to withdraw material from the body for analysis. For
example, when a nodule is felt in the thyroid, fine
needle aspiration may be done to remove a tissue
sample that can be examined to determine whether
the nodule is benign or malignant. The aspirated
material is examined under the microscope by a
pathologist.
fingernail
A covering for the tip of the finger that
is produced by living skin cells in the finger. A fin-
gernail consists of several parts, including the nail
plate (the visible part of the nail), the nail bed (the
skin beneath the nail plate), the cuticle (the tissue
that overlaps the plate and rims the base of the
nail), the nail folds (the skin folds that frame and
support the nail on three sides), the lunula (the
whitish half-moon at the base of the nail), and
the matrix (the hidden part of the nail unit under
the cuticle). A fingernail grows from the matrix and
is composed largely of keratin, a hardened protein
that is also found in skin and hair. See also 
nail;
nail care.
fingers, six
See 
hexadactyly.
fire, St. Anthony’s
An intensely painful burning
sensation in the limbs and extremities that is caused
by ergot, which is the consequence of a fungus
(Claviceps purpurea) that contaminates rye and
wheat. See also 
ergot.
fire ant
Originally from South America, a red or
yellowish ant of small to medium size that has a
severe sting that burns like fire. The sting of a fire
ant causes a pustule to form within 24 hours that
takes several days to resolve. Fire ant toxin can trig-
ger an allergic reaction, particularly in people aller-
gic to bee, wasp, and yellow jacket stings. Avoidance
and prompt treatment are essential.