Webster's New World Medical Dictionary

interstitial cystitis
See 
cystitis, interstitial.
interstitial radiation
See 
radiation therapy,
interstitial.
interstitial-cell-stimulating hormone (ICSH)
See 
luteinizing hormone.
intervening sequence
See 
intron.
interventional radiology
See 
radiology,
interventional.
interventricular foramen
An opening between
the lateral and third ventricles in the system of four
communicating cavities within the brain that are
continuous with the central canal of the spinal cord.
interventricular septum
The stout wall that
separates the lower chambers (the ventricles) of the
heart from one another. A hole in the interventricu-
lar septum is termed a ventricular septal defect
(VSD).
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interventricular septum
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intervertebral disc
A disk-shaped piece of spe-
cialized tissue that separates the bones of the spinal
column. Intervertebral discs form the intervertebral
joints and provide protection and shock absorbing
functions for the spine. The center of a disc, called
the nucleus, is soft, springy, and receives the shock
of standing, walking, running, etc. The outer ring of
the disc, called the 
annulus
(Latin for ring), pro-
vides structure and strength to the disc. The inter-
vertebral discs are susceptible to degenerative
changes associated with wear and tear or aging, and
a disc can herniate or rupture. A herniated disc is
often referred to as a slipped disc. This term comes
from the action of the nuclear tissue when it is
forced from the center of the disc. The nuclear tis-
sue located in the center of the disc can be placed
under so much pressure that it can cause the annu-
lus to rupture. When the disc has herniated or rup-
tured, it may create pressure against one or more of
the spinal nerves, which can cause pain, weakness,
or numbness. Also known as intervertebral disk.