Latent period The time when an illness is developing but
overt signs and symptoms are not apparent.Lectins Glycoproteins that bind to carbohydrate residues
on macromolecules or cell membranes.Lesions Structural or functional abnormalities.Leukocyte One of several types of white blood cell each
with its own function.Leukocytosis Leukocytecount in excess of 20q 109 dm–3
compared with reference values of 4–11q 109 dm–3.Leukodepletion Removal of leukocytesfrom blood by
filtering it through leukocyte-specific filters which
trap the leukocytes but not the smallererythrocytes
or platelets, and reduces the leukocyte count to less
than 5q 106 dm–3.Leukopheresis The removal of leukocytes from blood with
the resulting plasma and erythrocytes being returned
to the blood donor (seeapheresis, plasmapheresis
andplateletpheresis).Life expectancy The average length of life of individuals
in a population.Lipofuscins Yellow-brown pigments produced by degen-
eration of cell membranes and organelles, probably
by the free radical peroxidation of membrane lipids.Lipoprotein particles Complexes of cholesterol, triacyl-
glycerols and proteins involved in transport of these
lipids in the blood. They occur as high density lipopro-
tein (HDL), low density lipoprotein (LDL)and very low
density lipoprotein particles (VLDL). Chylomicrons
formed from fatty materials absorbed by the gastroin-
testinal tract are also lipoprotein particles.Lower reference nutrient intake (LRNI) The amount of a
nutrient sufficient for the requirements of 2.5% of a
population (compare withestimated average require-
ment,reference nutrient intakeandsafe intake).Lymphocytes Mononuclear leukocytes that occur in
the blood as large granular lymphocytes and small
lymphocytes.Lymphoid stem cells Hemopoietic stem cells found in
bone marrow which can divide to produce the precur-
sors ofsmall lymphocytes.Lymphoma A tumor that arises from lymphoid tissue,
such as a lymph node.Lymphopenia A reducedlymphocytecount.Macrophages Immune cells that differentiate in solid tis-
sues from immaturemonocytes.Major Histocompatibility Complex (MHC) A region of
the chromosome that encodes membrane proteins
which present antigenic peptides derived from pro-teins on the surfaces of antigen-presenting cells to T
lymphocytes.Malignant tumor Seecancer.Mammography An X-ray examination of the breast.Marasmus A chronic disorder that develops over a period
of months to years caused by an inadequate protein-
energy intake (seekwashiorkor).Mast cell A type of granule-containing white blood cell
that resembles abasophilbut which is found in solid
tissues.Medical microbiology The science concerned with
the detection and identification of pathogenic
microorganisms.Megakaryocytes Large precursor cells from the bone
marrow that eventually fragment to formplateletsin
the blood.Meiosis Reduction division. The type of cell division in
which the daughter cells receive only one of each type
of chromosome and which results in the formation of
haploidgametes (seemitosis).Membrane Attack Complex (MAC) This is a large, cylin-
drical, hydrophobic structure constructed from single
complement protein molecules (C5b, C6, C7, C8)
along with several molecules of C9. It can insert itself
into a cell membrane leading to cell lysis.Mesentery The double-layered, fan-shaped portion of
peritoneumthat extends from the posterior abdomi-
nal wall and wraps around the small intestine and
returns to its origin and contains the blood and lym-
phatic vessels and nerves that supply the small intes-
tine (see alsomesocolon).Mesocolon The structure with similar functions to the
mesenterybut which holds the large intestine.Metabolic acid–base disorder This is the occurrence of an
abnormal blood pH because of a metabolic or renal
dysfunction (seerespiratory acid–base disorder).Metastasis The detachment of cells from aprimary tumor
allowing it to spread and formsecondary tumors.Methemoglobin Oxidation of ferrous (Fe(II)) iron in the
heme group of hemoglobin to Fe(III) iron produces
methemoglobin which is incapable of carrying
oxygen.Mitogens Substances that stimulate cells to divide.See
mitosis.Mitosis The type of cell division in which each of the
daughter cells receives a full complement of chromo-
somes (seemeiosis).GLOSSARYmmk^ W^dad\nd[Y^hZVhZ