Webster's New World Medical Dictionary

pantothenic acid
Vitamin B5. See also Appendix
C, “Vitamins.”
Pap test
A screening test for cervical cancer that
involves the microscopic examination of cells col-
lected from the cervix, smeared on a slide, and spe-
cially stained. A Pap test can reveal premalignant
and malignant changes in the cells, as well as
changes that are due to noncancerous conditions,
such as inflammation. Named after the physician
George Papanicolaou, who developed the test. Also
known as Pap smear.
papilla, fungiform
See 
fungiform papillae.
papillary muscle
See 
muscle, papillary.
papillary tumor
A tumor that is shaped like a
small mushroom, with its “stem” attached to an
organ, such as the inner lining of the bladder.
papilledema
Swelling of the head of the optic
nerve, a sign of increased pressure within the skull.
The optic nerve head is the area where the optic
nerve (the nerve that carries information from the
retina to the brain) enters the eyeball. Papilledema is
diagnosed through use of an ophthalmoscope.
The optic nerve head is abnormally elevated in
papilledema, almost always in both eyes. The causes
of papilledema include swelling of the brain (as from
encephalitis or trauma), tumors and other lesions
that occupy space within the skull, increased pro-
duction of cerebrospinal fluid (CSF), decreased
resorption of CSF (due to meningitis, venous sinus
thrombosis, or subarachnoid hemorrhage), obstruc-
tion of the ventricular system within the brain, hydro-
cephalus, craniosynostosis (premature closure of the
sutures of the skull), and pseudotumor cerebri
(increased pressure within the brain in the absence
of a tumor). When papilledema is found, the patient
requires immediate further evaluation and, if needed,
intervention. Also known as a choked disk. See also
brain cancer; cerebrospinal fluid; craniosynosto-
sis; encephalitis; hydrocephalus; meningitis;
pseudotumor cerebri; ventricle, cerebral.
papilloma
A small solid benign tumor with a
clear-cut border that projects above the surrounding
tissue. A raised wart is an example of a papilloma.