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GLOSSARY 297

Mesenteric veins Blood vessel that drains blood from the Mononucleosis Acute infectious disease caused most fre-
small intestine (jejunum and ileum). quently by the Epstein-Barr virus of the herpes virus group;
Metacercaria Encysted stage of the life cycle of a trematode characterized by swollen lymph nodes and elevated and abnor-
(flatworm) which occurs in an intermediate host and then in- mal presence of lymphocytes.
fects the definitive host. Morbidity Pertains to disease states as a statistical value of the
Metastasis Change in location of a disease by movement of number of cases in a certain population group (often accom-
bacteria or diseased body cells to another location. panied by mortality rates or the number of deaths for a given
Metazoan This form of life is multicellular, in comparison disease).
with the protozoan, a one-celled organism. Morphology Structure and shape of an element, such as a
Methylene blue This dye is used in a variety of staining pro- cell or organism.
cedures for bacteria, cells, and parasites. Mortality The condition of being mortal means a susceptibil-
Microcrustacean copecods Copepods are a group of small ity to experience death.
crustaceans found in the sea and nearly every freshwater habi- Motility Ability to move from one location to another.
tat. These organisms are the hosts for certain stages of parasitic Mucocutaneous Area of the skin which contains mucus
development, and when eaten by fish are able to transmit the membranes.
organisms to others. Multicellular This term refers to the opposite of unicellular,
Microfilaria Immature form of the filarial worm. meaning that an organism is composed of more than one cell.
Microgametes The male version of the gamete for conju- Multivesicular The term refers to numerous small vesicles
gation in the protozoa, specifically in the Plasmodium spp. or blisters.
reproductive process. Mutualism Parasitic relationship where both organisms ben-
Microgametocytes The gametocytes for the male reproduc- efit from association.
tive structure is the microgametocyte and the larger, the female Myalgia Refers to muscle pain.
macrogametocyte, are ingested by an Anopheles mosquito dur- Myeloproliferative disorders Refers to atypical prolifera-
ing a blood meal. tion of the stem cells that provide blood production.
Microsporidia Once thought to be protists, the microspo-
ridia are now known to be fungi and constitute a phylum of N
spore-forming unicellular parasites.
Microvilli Refers to an increase in the exposed surface of a Nagana A disease caused by Trypanosoma brucei, and which
living organism or cell by the presence of hair, pilli, or folds may affect humans, horses, and other animals; transmitted by
that increase surface area. the tsetse fly.
Miracidia Larvae that are free-swimming and that arise from Nemanthelminthes Refers to roundworms, organisms of
a digenetic fluke (undergoes either sexual and asexual repro- the phylum Nemanthelminthes.
duction alternately). After leaving the egg, it infects a particu- Nematodes Refers to the parasites that are roundworms.
lar species of snail and becomes a sprorocyst. Neorickettsia This strain includes species that are coccoid or
Mites Small arachnid, some of which are parasitic, and cause pleomorphic cells found in cytoplasmic vacuoles within mono-
or aggravate conditions such as allergies, asthma, mange, cytes and macrophages of dogs, horses, bats, and humans.
and scabies; occasionally are intermediate hosts for certain Nephrosis The condition is also called nephrotic syndrome
cestodes. or nephropathy, and is a kidney disease characterized by de-
Mitochondrion A rod-shaped or oval-shaped organelle of a generative lesions of the renal tubules.
cell; participate in aerobic respiration of the cell. Neurocysticercosis Cysticercosis, which is also called neu-
Mode of transmission Refers to the manner in which trans- rocysticercosis, is the most common parasitic infestation of the
mission takes place (e.g., eating poorly cooked beef containing central nervous system worldwide.
larvae). Neutrophils White blood cell with a segmented nucleus; re-
Mollusks Invertebrate animals of the phylum Mollusca; found sponds primarily to bacterial infections.
mostly in water and most often have a hard and protective outer NHANES National Health and Nutrition Examination
shell. They have a muscular foot for locomotion and a well-defined Survey.
circulatory and nervous system. Mollusks include gastropods that Nit The egg of a louse or other parasitic insect; often visible
are important in parasite transmission as an intermediate host. when head or body lice lay eggs on a hair shaft.
Molt Term used to describe an activity related to growth Norwegian scabies A strain of scabies; a contagious ec-
or change of season, and means to cast or shed the feathers, toparasite skin infection characterized by superficial burrows
scales, and skin. and intense pruritus (itching), that is characterized by larger
Monogenea Type of flatworm that lives on the outside of their number of organisms than for other strains of the mite.
host. They are not free-living and always need another creature Nucleus or nuclei Structure(s) normally at the center of
to which to live. a cell that contains the chromosomes with DNA and RNA
Mononuclear cells Cells that have only one nucleus, or a and is/are responsible for the cellular metabolism, growth,
nonsegmented nucleus. excretion, and production.