Webster's New World Medical Dictionary

septum, heart
See 
septum, cardiac.
septum, interatrial
See 
septum, atrial.
septum, interventricular
See 
septum,
ventricular.
septum, nasal
The dividing wall that runs down
the middle of the nose, creating two nasal passages,
each ending in a nostril.
septum, ventricular
The wall between the two
lower chambers (ventricles) of the heart. Also
known as interventricular septum.
sequencing
Determining the order of nucleotides
(base sequences) in a DNA or RNA molecule, or
determining the order of amino acids in a protein.
SERM
Selective estrogen-receptor modulator.
seroconversion
The development of detectable
antibodies in the blood that are directed against an
infectious agent. Antibodies do not usually develop
until some time after the initial exposure to the
agent. Following seroconversion, a person tests pos-
itive for the antibody when given tests that are based
on the presence of antibodies, such as ELISA.
serositis
Inflammation of the serous tissues of
the body (the tissues that line the lungs, heart,
abdomen, and inner abdominal organs).
serotonin
A neurotransmitter that is involved in
the transmission of nerve impulses. Serotonin can
trigger the release of substances in the blood vessels
of the brain that in turn cause the pain of migraine.
Serotonin is also key to mood regulation; pain per-
ception; gastrointestinal function, including percep-
tion of hunger and satiety; and other physical
functions.
serotype
A subdivision of a particular species of
microorganism characterized by identification of
recognizable antigens on its surface.
serous membrane
The tissue that lines the cavi-
ties containing the lungs (pleural cavity) and heart
(pericardial cavity), the cavity containing most of the
abdominal organs (peritoneal cavity), and that cov-
ers the surfaces of many internal organs. Serous
membranes act as a protective lining by providing a