Definitions and descriptions

Definitions and descriptions

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There are currently 39 terms in this directory beginning with the letter N.
Nail follicle (NAYL FAH-li-kuhl)
The structure within the skin of a finger or toe in which a nail grows; mitosis takes place in the nail root
Narrow spectrum (NAR-oh SPEK-trum)
An antibiotic that is effective against only a few kinds of bacteria
Nasal cavities (NAY-zuhl KAV-i-tees)
The two air cavities within the skull through which air passes from the nostrils to the nasopharynx; separated by the nasal septum
Nasal mucosa (NAY-zuhl mew-KOH-sah)
The lining of the nasal cavities; made of ciliated epithelium that warms and moistens the incoming air and sweeps mucus, dust, and pathogens toward the nasopharynx
Nasal septum (NAY-zuhl SEP-tum)
The vertical plate made of bone and cartilage that separates the two nasal cavities
Nasopharyngeal Cancer
Nasopharyngeal carcinoma is the predominant tumor type arising in the epithelium of the nasopharynx.
Nasopharynx (NAY-zo-FA-rinks)
The upper portion of the pharynx above the level of the soft palate; an air passageway
Natural killer cell (NATCH-er-al KILL-er SELL)
A type of lymphocyte that is not specific and is part of innate immunity; kills pathogens and tumor cells by direct contact
Necrotizing Fasciitis
Life threatening progressive rapidly spreading inflammatory infection located in deep fascia, most commonly caused by Streptococcus species or polymicrobial.
Necrotizing fasciitis (NEK-roh-ty-zing FASH-ee-EYEtis)
An acute, fulminant, and potentially fatal infection of fasciae often caused by Group A streptococci
Negative feedback mechanism (NEG-ah-tiv FEED-bak)
A control system in which a stimulus initiates a response that reverses or reduces the stimulus, thereby stopping the response until the stimulus occurs again and there is a need for the response
Neonatal Conjunctivitis (Ophthalmia Neonatorum)
Ophthalmia Neonatorum (ON) means inflammation of the conjunctival of a newborn baby of less than 1 month of age. This is a potentially sight threatening condition.
Neonatal herpes (NEE-oh-NAY-tal HER-peez)
A herpes simplex infection in a newborn; may cause encephalitis and may be fatal
Neonatal tetanus
Usually occurs through introduction of tetanus spores via the umblical cord during delivery through the use of unclean instruments to cut the cord, or after delivery by "dressing" the umblical stump with substances heavily contaminated with tetanus spores.
Nephritis (ne-FRY-tis)
Inflammation of the kidney; may be caused by bacterial infection or toxic chemicals
Nephron (NEFF-ron)
The structural and functional unit of the kidney that forms urine; consists of a renal corpuscle and a renal tubule
Nerve (NERV)
A group of neurons, together with blood vessels and connective tissue
Nerve tissue (NERV TISH-yoo)
The tissue specialized to generate and transmit electrochemical impulses that have many functions in the maintenance of homeostasis
Nerve tract (NERV TRAKT)
A group of neurons that share a common function within the central nervous system; a tract may be ascending (sensory) or descending (motor)
Nervous system (NERV-us SIS-tem)
The organ system that regulates body functions by means of electrochemical impulses; consists of the brain, spinal cord, cranial nerves, and spinal nerves
Neuralgia (new-RAL-jee-ah)
Sharp, severe pain along the course of a nerve
Neuritis (new-RYE-tis)
Inflammation of a nerve
Neuroglia (new-ROG-lee-ah)
The non-neuronal cells of the central nervous system; produce the myelin sheath and contribute to the blood–brain barrier, among other functions
Neurohypophysis (NEW-roo-high-POFF-e-sis)
The posterior pituitary gland
Neurolemma (NEW-roh-LEM-ah)
The sheath around peripheral axons and dendrites, formed by the cytoplasm and nuclei of Schwann cells; is essential for the regeneration of damaged peripheral neurons
Neuromuscular junction (NYOOR-oh-MUSS-kew-lar JUNK-shun)
The termination of a motor neuron on the sarcolemma of a muscle fiber; the synapse is the microscopic space between the two structures
Neuron (NYOOR-on)
A nerve cell; consists of a cell body, an axon, and dendrites
Neuropathy (new-RAH-puh-thee)
Any disease or disorder of the nerves; may be primary, such as shingles or rabies, or secondary, such as diabetic neuropathy
Neurotoxin (NEW-roh-TOK-sin)
A chemical that disrupts an aspect of the functioning of the nervous system
Neurotransmitter (NYOOR-oh-TRANS-mih-ter)
A chemical released by the axon of a neuron, which crosses a synapse and affects the electrical activity of the postsynaptic membrane (neuron or muscle cell or gland)
Neutron (NEW-trahn)
A subatomic particle that has no electrical charge; found in the nucleus of an atom
Neutrophil (NEW-troh-fill)
A type of granular white blood cell; capable of phagocytosis of pathogens
Non-odontogenic jaw cysts
A group of cysts arising from epithelial remnants of embryonic ducts left behind after embryonal facial and jaw development; they are located deep within the tissues in the region of former epithelial ridges, epithelial walls, and primary facial fissural and cleft structures.
Non-ST Elevation Myocardial Infarction (NSTEMI)
Non-ST Elevation Myocardial Infarction is a medical emergency characterized with chest pain that is increasing in frequency and/or severity or occurring at rest, associated with elevated cardiac enzymes and ST segment depression or T wave inversion or normal ECG.
Non-ulcer Dyspepsia (Functional Dyspepsia)
It is a chronic recurrent dyspeptic disorder characterized by epigastric pain syndrome and post prandial distress syndrome without any organic, systemic or metabolic disease to explain its presence.
Nonionizing radiation.
Ultra-violet (UV) rays (280–200 nm) are a type of nonionizing radiation that is rapidly absorbed by a variety of materials. UV rays are therefore used only to reduce airborne pathogen counts (surgical theaters, filling equipment) and for disinfection of smooth surfaces.
Nose bleeding (Epistaxis)
Nose bleeding is a condition which is common in adults. It may be due to a local cause in the nasal cavity (e.g. trauma, tumor, foreign body, septal verisces or septal deviation); or a systemic cause (e.g. blood disorders, vascular disorders, renal failure, hepatic failure, or use of anticoagulants (warfarin, heparin). Most cases of epistaxis are minor; do not require hospitalization.
Nosocomial infection
Infection acquired during hospitalization (urinary tract infections, infections of the respiratory organs, wound infection, sepsis)
Nucleus (NEW-klee-us)
1. The membrane bound part of a cell that contains the hereditary material in chromosomes.

2. The central part of an atom containing protons and neutrons
Gafacom
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