Webster's New World Medical Dictionary

particularly helpful in the diagnosis of inflammatory
diseases of the central nervous system (CNS), espe-
cially meningitis and other infections. It can also
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lumbar puncture
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provide clues to the diagnosis of stroke, spinal cord
tumor, and cancer in the CNS. An LP can also be
done for therapeutic purposes, as a way of adminis-
tering antibiotics, cancer drugs, or anesthetic agents
into the spinal canal. Spinal fluid is sometimes
removed via LP to decrease spinal fluid pressure in
patients with conditions such as normal-pressure
hydrocephalus or benign intracranial hypertension.
Risks related to LP include headache, brain hernia-
tion, bleeding, and infection. These complications
are uncommon, with the exception of headache,
which can appear up to a day after LP. Headaches
are less likely to occur if the patient remains lying
flat for 1 to 3 hours after the procedure. Also known
as spinal tap, spinal puncture, thecal puncture, and
rachiocentesis.
lumbar vertebrae
The five vertebrae situated
between the thoracic vertebrae and the sacral verte-
brae in the spinal column. The lumbar vertebrae are
represented by the symbols L1 through L5.
lumpectomy
The surgical removal of a small
tumor, which may be benign or cancerous. In com-
mon use, lumpectomy refers especially to removal
of a lump from the breast. Lumpectomy, often with
chemotherapy or radiation therapy, can be an alter-
native to mastectomy in cases of nonmetastatic
breast cancer.
lung
One of a pair of three-lobed breathing
organs located within the right and left sides of the
chest. The lungs remove carbon dioxide from the
blood and bring oxygen into the blood. Air comes
into the lungs via the trachea, traveling evenly into
the left and right lungs by means of the left and right
bronchi. Each bronchus branches off into several
smaller bronchioles, which end in many alveolar
sacs. In the tiny alveoli within these sacs, oxygen is
exchanged for carbon dioxide in blood delivered
back to the heart by the pulmonary veins. Lung
function is controlled by several muscles, including
the diaphragm muscle beneath the lungs and the
intercostal muscles that surround the lungs.